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[merged] libfs-fix-infoleak-in-simple_attr_read.patch removed from -mm tree

by akpm＠linux-foundation.org

The patch titled Subject: libfs: fix infoleak in simple_attr_read() has been removed from the -mm tree. Its filename was libfs-fix-infoleak-in-simple_attr_read.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Eric Biggers <ebiggers(a)google.com> Subject: libfs: fix infoleak in simple_attr_read() Reading from a debugfs file at a nonzero position, without first reading at position 0, leaks uninitialized memory to userspace. It's a bit tricky to do this, since lseek() and pread() aren't allowed on these files, and write() doesn't update the position on them. But writing to them with splice() *does* update the position: #define _GNU_SOURCE 1 #include <fcntl.h> #include <stdio.h> #include <unistd.h> int main() { int pipes[2], fd, n, i; char buf[32]; pipe(pipes); write(pipes[1], "0", 1); fd = open("/sys/kernel/debug/fault_around_bytes", O_RDWR); splice(pipes[0], NULL, fd, NULL, 1, 0); n = read(fd, buf, sizeof(buf)); for (i = 0; i < n; i++) printf("%02x", buf[i]); printf(" "); } Output: 5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a5a30 Fix the infoleak by making simple_attr_read() always fill simple_attr::get_buf if it hasn't been filled yet. Link: http://lkml.kernel.org/r/20200308023849.988264-1-ebiggers@kernel.org Fixes: acaefc25d21f ("[PATCH] libfs: add simple attribute files") Signed-off-by: Eric Biggers <ebiggers(a)google.com> Reported-by: syzbot+fcab69d1ada3e8d6f06b(a)syzkaller.appspotmail.com Reported-by: Alexander Potapenko <glider(a)google.com> Cc: Al Viro <viro(a)zeniv.linux.org.uk> Cc: Arnd Bergmann <arnd(a)arndb.de> Cc: Greg Kroah-Hartman <gregkh(a)linuxfoundation.org> Cc: "Rafael J. Wysocki" <rafael(a)kernel.org> Cc: Kees Cook <keescook(a)chromium.org> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> --- fs/libfs.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/fs/libfs.c~libfs-fix-infoleak-in-simple_attr_read +++ a/fs/libfs.c @@ -891,7 +891,7 @@ int simple_attr_open(struct inode *inode { struct simple_attr *attr; - attr = kmalloc(sizeof(*attr), GFP_KERNEL); + attr = kzalloc(sizeof(*attr), GFP_KERNEL); if (!attr) return -ENOMEM; @@ -931,9 +931,11 @@ ssize_t simple_attr_read(struct file *fi if (ret) return ret; - if (*ppos) { /* continued read */ + if (*ppos && attr->get_buf[0]) { + /* continued read */ size = strlen(attr->get_buf); - } else { /* first read */ + } else { + /* first read */ u64 val; ret = attr->get(attr->data, &val); if (ret) _ Patches currently in -mm which might be from ebiggers(a)google.com are kmod-make-request_module-return-an-error-when-autoloading-is-disabled.patch fs-filesystemsc-downgrade-user-reachable-warn_once-to-pr_warn_once.patch docs-admin-guide-document-the-kernelmodprobe-sysctl.patch selftests-kmod-fix-handling-test-numbers-above-9.patch selftests-kmod-test-disabling-module-autoloading.patch

5 years, 7 months

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[merged] x86-mm-split-vmalloc_sync_all.patch removed from -mm tree

by akpm＠linux-foundation.org

The patch titled Subject: x86/mm: split vmalloc_sync_all() has been removed from the -mm tree. Its filename was x86-mm-split-vmalloc_sync_all.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Joerg Roedel <jroedel(a)suse.de> Subject: x86/mm: split vmalloc_sync_all() Commit 3f8fd02b1bf1 ("mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy()") introduced a call to vmalloc_sync_all() in the vunmap() code-path. While this change was necessary to maintain correctness on x86-32-pae kernels, it also adds additional cycles for architectures that don't need it. Specifically on x86-64 with CONFIG_VMAP_STACK=y some people reported severe performance regressions in micro-benchmarks because it now also calls the x86-64 implementation of vmalloc_sync_all() on vunmap(). But the vmalloc_sync_all() implementation on x86-64 is only needed for newly created mappings. To avoid the unnecessary work on x86-64 and to gain the performance back, split up vmalloc_sync_all() into two functions: * vmalloc_sync_mappings(), and * vmalloc_sync_unmappings() Most call-sites to vmalloc_sync_all() only care about new mappings being synchronized. The only exception is the new call-site added in the above mentioned commit. Shile Zhang directed us to a report of an 80% regression in reaim throughput. Link: http://lkml.kernel.org/r/20191009124418.8286-1-joro@8bytes.org Link: https://lists.01.org/hyperkitty/list/lkp@lists.01.org/thread/4D3JPPHBNOSPFK… Link: http://lkml.kernel.org/r/20191113095530.228959-1-shile.zhang@linux.alibaba.… Fixes: 3f8fd02b1bf1 ("mm/vmalloc: Sync unmappings in __purge_vmap_area_lazy()") Signed-off-by: Joerg Roedel <jroedel(a)suse.de> Reported-by: kernel test robot <oliver.sang(a)intel.com> Reported-by: Shile Zhang <shile.zhang(a)linux.alibaba.com> Acked-by: Rafael J. Wysocki <rafael.j.wysocki(a)intel.com> [GHES] Tested-by: Borislav Petkov <bp(a)suse.de> Cc: Dave Hansen <dave.hansen(a)linux.intel.com> Cc: Andy Lutomirski <luto(a)kernel.org> Cc: Peter Zijlstra <peterz(a)infradead.org> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Ingo Molnar <mingo(a)redhat.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> --- arch/x86/mm/fault.c | 26 ++++++++++++++++++++++++-- drivers/acpi/apei/ghes.c | 2 +- include/linux/vmalloc.h | 5 +++-- kernel/notifier.c | 2 +- mm/nommu.c | 10 +++++++--- mm/vmalloc.c | 11 +++++++---- 6 files changed, 43 insertions(+), 13 deletions(-) --- a/arch/x86/mm/fault.c~x86-mm-split-vmalloc_sync_all +++ a/arch/x86/mm/fault.c @@ -190,7 +190,7 @@ static inline pmd_t *vmalloc_sync_one(pg return pmd_k; } -void vmalloc_sync_all(void) +static void vmalloc_sync(void) { unsigned long address; @@ -217,6 +217,16 @@ void vmalloc_sync_all(void) } } +void vmalloc_sync_mappings(void) +{ + vmalloc_sync(); +} + +void vmalloc_sync_unmappings(void) +{ + vmalloc_sync(); +} + /* * 32-bit: * @@ -319,11 +329,23 @@ out: #else /* CONFIG_X86_64: */ -void vmalloc_sync_all(void) +void vmalloc_sync_mappings(void) { + /* + * 64-bit mappings might allocate new p4d/pud pages + * that need to be propagated to all tasks' PGDs. + */ sync_global_pgds(VMALLOC_START & PGDIR_MASK, VMALLOC_END); } +void vmalloc_sync_unmappings(void) +{ + /* + * Unmappings never allocate or free p4d/pud pages. + * No work is required here. + */ +} + /* * 64-bit: * --- a/drivers/acpi/apei/ghes.c~x86-mm-split-vmalloc_sync_all +++ a/drivers/acpi/apei/ghes.c @@ -171,7 +171,7 @@ int ghes_estatus_pool_init(int num_ghes) * New allocation must be visible in all pgd before it can be found by * an NMI allocating from the pool. */ - vmalloc_sync_all(); + vmalloc_sync_mappings(); rc = gen_pool_add(ghes_estatus_pool, addr, PAGE_ALIGN(len), -1); if (rc) --- a/include/linux/vmalloc.h~x86-mm-split-vmalloc_sync_all +++ a/include/linux/vmalloc.h @@ -141,8 +141,9 @@ extern int remap_vmalloc_range_partial(s extern int remap_vmalloc_range(struct vm_area_struct *vma, void *addr, unsigned long pgoff); -void vmalloc_sync_all(void); - +void vmalloc_sync_mappings(void); +void vmalloc_sync_unmappings(void); + /* * Lowlevel-APIs (not for driver use!) */ --- a/kernel/notifier.c~x86-mm-split-vmalloc_sync_all +++ a/kernel/notifier.c @@ -519,7 +519,7 @@ NOKPROBE_SYMBOL(notify_die); int register_die_notifier(struct notifier_block *nb) { - vmalloc_sync_all(); + vmalloc_sync_mappings(); return atomic_notifier_chain_register(&die_chain, nb); } EXPORT_SYMBOL_GPL(register_die_notifier); --- a/mm/nommu.c~x86-mm-split-vmalloc_sync_all +++ a/mm/nommu.c @@ -370,10 +370,14 @@ void vm_unmap_aliases(void) EXPORT_SYMBOL_GPL(vm_unmap_aliases); /* - * Implement a stub for vmalloc_sync_all() if the architecture chose not to - * have one. + * Implement a stub for vmalloc_sync_[un]mapping() if the architecture + * chose not to have one. */ -void __weak vmalloc_sync_all(void) +void __weak vmalloc_sync_mappings(void) +{ +} + +void __weak vmalloc_sync_unmappings(void) { } --- a/mm/vmalloc.c~x86-mm-split-vmalloc_sync_all +++ a/mm/vmalloc.c @@ -1295,7 +1295,7 @@ static bool __purge_vmap_area_lazy(unsig * First make sure the mappings are removed from all page-tables * before they are freed. */ - vmalloc_sync_all(); + vmalloc_sync_unmappings(); /* * TODO: to calculate a flush range without looping. @@ -3128,16 +3128,19 @@ int remap_vmalloc_range(struct vm_area_s EXPORT_SYMBOL(remap_vmalloc_range); /* - * Implement a stub for vmalloc_sync_all() if the architecture chose not to - * have one. + * Implement stubs for vmalloc_sync_[un]mappings () if the architecture chose + * not to have one. * * The purpose of this function is to make sure the vmalloc area * mappings are identical in all page-tables in the system. */ -void __weak vmalloc_sync_all(void) +void __weak vmalloc_sync_mappings(void) { } +void __weak vmalloc_sync_unmappings(void) +{ +} static int f(pte_t *pte, unsigned long addr, void *data) { _ Patches currently in -mm which might be from jroedel(a)suse.de are

5 years, 7 months

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[merged] mm-slub-prevent-kmalloc_node-crashes-and-memory-leaks.patch removed from -mm tree

by akpm＠linux-foundation.org

The patch titled Subject: mm, slub: prevent kmalloc_node crashes and memory leaks has been removed from the -mm tree. Its filename was mm-slub-prevent-kmalloc_node-crashes-and-memory-leaks.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Vlastimil Babka <vbabka(a)suse.cz> Subject: mm, slub: prevent kmalloc_node crashes and memory leaks Sachin reports [1] a crash in SLUB __slab_alloc(): BUG: Kernel NULL pointer dereference on read at 0x000073b0 Faulting instruction address: 0xc0000000003d55f4 Oops: Kernel access of bad area, sig: 11 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries Modules linked in: CPU: 19 PID: 1 Comm: systemd Not tainted 5.6.0-rc2-next-20200218-autotest #1 NIP: c0000000003d55f4 LR: c0000000003d5b94 CTR: 0000000000000000 REGS: c0000008b37836d0 TRAP: 0300 Not tainted (5.6.0-rc2-next-20200218-autotest) MSR: 8000000000009033 <SF,EE,ME,IR,DR,RI,LE> CR: 24004844 XER: 00000000 CFAR: c00000000000dec4 DAR: 00000000000073b0 DSISR: 40000000 IRQMASK: 1 GPR00: c0000000003d5b94 c0000008b3783960 c00000000155d400 c0000008b301f500 GPR04: 0000000000000dc0 0000000000000002 c0000000003443d8 c0000008bb398620 GPR08: 00000008ba2f0000 0000000000000001 0000000000000000 0000000000000000 GPR12: 0000000024004844 c00000001ec52a00 0000000000000000 0000000000000000 GPR16: c0000008a1b20048 c000000001595898 c000000001750c18 0000000000000002 GPR20: c000000001750c28 c000000001624470 0000000fffffffe0 5deadbeef0000122 GPR24: 0000000000000001 0000000000000dc0 0000000000000002 c0000000003443d8 GPR28: c0000008b301f500 c0000008bb398620 0000000000000000 c00c000002287180 NIP [c0000000003d55f4] ___slab_alloc+0x1f4/0x760 LR [c0000000003d5b94] __slab_alloc+0x34/0x60 Call Trace: [c0000008b3783960] [c0000000003d5734] ___slab_alloc+0x334/0x760 (unreliable) [c0000008b3783a40] [c0000000003d5b94] __slab_alloc+0x34/0x60 [c0000008b3783a70] [c0000000003d6fa0] __kmalloc_node+0x110/0x490 [c0000008b3783af0] [c0000000003443d8] kvmalloc_node+0x58/0x110 [c0000008b3783b30] [c0000000003fee38] mem_cgroup_css_online+0x108/0x270 [c0000008b3783b90] [c000000000235aa8] online_css+0x48/0xd0 [c0000008b3783bc0] [c00000000023eaec] cgroup_apply_control_enable+0x2ec/0x4d0 [c0000008b3783ca0] [c000000000242318] cgroup_mkdir+0x228/0x5f0 [c0000008b3783d10] [c00000000051e170] kernfs_iop_mkdir+0x90/0xf0 [c0000008b3783d50] [c00000000043dc00] vfs_mkdir+0x110/0x230 [c0000008b3783da0] [c000000000441c90] do_mkdirat+0xb0/0x1a0 [c0000008b3783e20] [c00000000000b278] system_call+0x5c/0x68 This is a PowerPC platform with following NUMA topology: available: 2 nodes (0-1) node 0 cpus: node 0 size: 0 MB node 0 free: 0 MB node 1 cpus: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 node 1 size: 35247 MB node 1 free: 30907 MB node distances: node 0 1 0: 10 40 1: 40 10 possible numa nodes: 0-31 This only happens with a mmotm patch "mm/memcontrol.c: allocate shrinker_map on appropriate NUMA node" [2] which effectively calls kmalloc_node for each possible node. SLUB however only allocates kmem_cache_node on online N_NORMAL_MEMORY nodes, and relies on node_to_mem_node to return such valid node for other nodes since commit a561ce00b09e ("slub: fall back to node_to_mem_node() node if allocating on memoryless node"). This is however not true in this configuration where the _node_numa_mem_ array is not initialized for nodes 0 and 2-31, thus it contains zeroes and get_partial() ends up accessing non-allocated kmem_cache_node. A related issue was reported by Bharata (originally by Ramachandran) [3] where a similar PowerPC configuration, but with mainline kernel without patch [2] ends up allocating large amounts of pages by kmalloc-1k kmalloc-512. This seems to have the same underlying issue with node_to_mem_node() not behaving as expected, and might probably also lead to an infinite loop with CONFIG_SLUB_CPU_PARTIAL [4]. This patch should fix both issues by not relying on node_to_mem_node() anymore and instead simply falling back to NUMA_NO_NODE, when kmalloc_node(node) is attempted for a node that's not online, or has no usable memory. The "usable memory" condition is also changed from node_present_pages() to N_NORMAL_MEMORY node state, as that is exactly the condition that SLUB uses to allocate kmem_cache_node structures. The check in get_partial() is removed completely, as the checks in ___slab_alloc() are now sufficient to prevent get_partial() being reached with an invalid node. [1] https://lore.kernel.org/linux-next/3381CD91-AB3D-4773-BA04-E7A072A63968@lin… [2] https://lore.kernel.org/linux-mm/fff0e636-4c36-ed10-281c-8cdb0687c839@virtu… [3] https://lore.kernel.org/linux-mm/20200317092624.GB22538@in.ibm.com/ [4] https://lore.kernel.org/linux-mm/088b5996-faae-8a56-ef9c-5b567125ae54@suse.… Link: http://lkml.kernel.org/r/20200320115533.9604-1-vbabka@suse.cz Fixes: a561ce00b09e ("slub: fall back to node_to_mem_node() node if allocating on memoryless node") Signed-off-by: Vlastimil Babka <vbabka(a)suse.cz> Reported-by: Sachin Sant <sachinp(a)linux.vnet.ibm.com> Tested-by: Sachin Sant <sachinp(a)linux.vnet.ibm.com> Reported-by: PUVICHAKRAVARTHY RAMACHANDRAN <puvichakravarthy(a)in.ibm.com> Tested-by: Bharata B Rao <bharata(a)linux.ibm.com> Debugged-by: Srikar Dronamraju <srikar(a)linux.vnet.ibm.com> Reviewed-by: Srikar Dronamraju <srikar(a)linux.vnet.ibm.com> Cc: Mel Gorman <mgorman(a)techsingularity.net> Cc: Michael Ellerman <mpe(a)ellerman.id.au> Cc: Michal Hocko <mhocko(a)kernel.org> Cc: Christopher Lameter <cl(a)linux.com> Cc: linuxppc-dev(a)lists.ozlabs.org Cc: Joonsoo Kim <iamjoonsoo.kim(a)lge.com> Cc: Pekka Enberg <penberg(a)kernel.org> Cc: David Rientjes <rientjes(a)google.com> Cc: Kirill Tkhai <ktkhai(a)virtuozzo.com> Cc: Vlastimil Babka <vbabka(a)suse.cz> Cc: Nathan Lynch <nathanl(a)linux.ibm.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> --- mm/slub.c | 26 +++++++++++++++++--------- 1 file changed, 17 insertions(+), 9 deletions(-) --- a/mm/slub.c~mm-slub-prevent-kmalloc_node-crashes-and-memory-leaks +++ a/mm/slub.c @@ -1973,8 +1973,6 @@ static void *get_partial(struct kmem_cac if (node == NUMA_NO_NODE) searchnode = numa_mem_id(); - else if (!node_present_pages(node)) - searchnode = node_to_mem_node(node); object = get_partial_node(s, get_node(s, searchnode), c, flags); if (object || node != NUMA_NO_NODE) @@ -2563,17 +2561,27 @@ static void *___slab_alloc(struct kmem_c struct page *page; page = c->page; - if (!page) + if (!page) { + /* + * if the node is not online or has no normal memory, just + * ignore the node constraint + */ + if (unlikely(node != NUMA_NO_NODE && + !node_state(node, N_NORMAL_MEMORY))) + node = NUMA_NO_NODE; goto new_slab; + } redo: if (unlikely(!node_match(page, node))) { - int searchnode = node; - - if (node != NUMA_NO_NODE && !node_present_pages(node)) - searchnode = node_to_mem_node(node); - - if (unlikely(!node_match(page, searchnode))) { + /* + * same as above but node_match() being false already + * implies node != NUMA_NO_NODE + */ + if (!node_state(node, N_NORMAL_MEMORY)) { + node = NUMA_NO_NODE; + goto redo; + } else { stat(s, ALLOC_NODE_MISMATCH); deactivate_slab(s, page, c->freelist, c); goto new_slab; _ Patches currently in -mm which might be from vbabka(a)suse.cz are revert-topology-add-support-for-node_to_mem_node-to-determine-the-fallback-node.patch mm-compaction-fully-assume-capture-is-not-null-in-compact_zone_order.patch mm-hugetlb-remove-unnecessary-memory-fetch-in-pageheadhuge.patch

5 years, 7 months

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[merged] epoll-fix-possible-lost-wakeup-on-epoll_ctl-path.patch removed from -mm tree

by akpm＠linux-foundation.org

The patch titled Subject: epoll: fix possible lost wakeup on epoll_ctl() path has been removed from the -mm tree. Its filename was epoll-fix-possible-lost-wakeup-on-epoll_ctl-path.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Roman Penyaev <rpenyaev(a)suse.de> Subject: epoll: fix possible lost wakeup on epoll_ctl() path This fixes possible lost wakeup introduced by commit a218cc491420. Originally modifications to ep->wq were serialized by ep->wq.lock, but in the a218cc491420 new rw lock was introduced in order to relax fd event path, i.e. callers of ep_poll_callback() function. After the change ep_modify and ep_insert (both are called on epoll_ctl() path) were switched to ep->lock, but ep_poll (epoll_wait) was using ep->wq.lock on wqueue list modification. The bug doesn't lead to any wqueue list corruptions, because wake up path and list modifications were serialized by ep->wq.lock internally, but actual waitqueue_active() check prior wake_up() call can be reordered with modifications of ep ready list, thus wake up can be lost. And yes, can be healed by explicit smp_mb(): list_add_tail(&epi->rdlink, &ep->rdllist); smp_mb(); if (waitqueue_active(&ep->wq)) wake_up(&ep->wp); But let's make it simple, thus current patch replaces ep->wq.lock with the ep->lock for wqueue modifications, thus wake up path always observes activeness of the wqueue correcty. Link: http://lkml.kernel.org/r/20200214170211.561524-1-rpenyaev@suse.de Fixes: a218cc491420 ("epoll: use rwlock in order to reduce ep_poll_callback() contention") References: https://bugzilla.kernel.org/show_bug.cgi?id=205933 Signed-off-by: Roman Penyaev <rpenyaev(a)suse.de> Reported-by: Max Neunhoeffer <max(a)arangodb.com> Bisected-by: Max Neunhoeffer <max(a)arangodb.com> Tested-by: Max Neunhoeffer <max(a)arangodb.com> Cc: Jakub Kicinski <kuba(a)kernel.org> Cc: Christopher Kohlhoff <chris.kohlhoff(a)clearpool.io> Cc: Davidlohr Bueso <dbueso(a)suse.de> Cc: Jason Baron <jbaron(a)akamai.com> Cc: Jes Sorensen <jes.sorensen(a)gmail.com> Cc: <stable(a)vger.kernel.org> [5.1+] Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> --- fs/eventpoll.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) --- a/fs/eventpoll.c~epoll-fix-possible-lost-wakeup-on-epoll_ctl-path +++ a/fs/eventpoll.c @@ -1854,9 +1854,9 @@ fetch_events: waiter = true; init_waitqueue_entry(&wait, current); - spin_lock_irq(&ep->wq.lock); + write_lock_irq(&ep->lock); __add_wait_queue_exclusive(&ep->wq, &wait); - spin_unlock_irq(&ep->wq.lock); + write_unlock_irq(&ep->lock); } for (;;) { @@ -1904,9 +1904,9 @@ send_events: goto fetch_events; if (waiter) { - spin_lock_irq(&ep->wq.lock); + write_lock_irq(&ep->lock); __remove_wait_queue(&ep->wq, &wait); - spin_unlock_irq(&ep->wq.lock); + write_unlock_irq(&ep->lock); } return res; _ Patches currently in -mm which might be from rpenyaev(a)suse.de are kselftest-introduce-new-epoll-test-case.patch

5 years, 7 months

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[merged] mm-do-not-allow-madv_pageout-for-cow-pages.patch removed from -mm tree

by akpm＠linux-foundation.org

The patch titled Subject: mm: do not allow MADV_PAGEOUT for CoW pages has been removed from the -mm tree. Its filename was mm-do-not-allow-madv_pageout-for-cow-pages.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Michal Hocko <mhocko(a)suse.com> Subject: mm: do not allow MADV_PAGEOUT for CoW pages Jann has brought up a very interesting point [1]. While shared pages are excluded from MADV_PAGEOUT normally, CoW pages can be easily reclaimed that way. This can lead to all sorts of hard to debug problems. E.g. performance problems outlined by Daniel [2]. There are runtime environments where there is a substantial memory shared among security domains via CoW memory and a easy to reclaim way of that memory, which MADV_{COLD,PAGEOUT} offers, can lead to either performance degradation in for the parent process which might be more privileged or even open side channel attacks. The feasibility of the latter is not really clear to me TBH but there is no real reason for exposure at this stage. It seems there is no real use case to depend on reclaiming CoW memory via madvise at this stage so it is much easier to simply disallow it and this is what this patch does. Put it simply MADV_{PAGEOUT,COLD} can operate only on the exclusively owned memory which is a straightforward semantic. [1] http://lkml.kernel.org/r/CAG48ez0G3JkMq61gUmyQAaCq=_TwHbi1XKzWRooxZkv08PQKu… [2] http://lkml.kernel.org/r/CAKOZueua_v8jHCpmEtTB6f3i9e2YnmX4mqdYVWhV4E=Z-n+zR… Link: http://lkml.kernel.org/r/20200312082248.GS23944@dhcp22.suse.cz Fixes: 9c276cc65a58 ("mm: introduce MADV_COLD") Signed-off-by: Michal Hocko <mhocko(a)suse.com> Reported-by: Jann Horn <jannh(a)google.com> Acked-by: Vlastimil Babka <vbabka(a)suse.cz> Cc: Minchan Kim <minchan(a)kernel.org> Cc: Daniel Colascione <dancol(a)google.com> Cc: Dave Hansen <dave.hansen(a)intel.com> Cc: "Joel Fernandes (Google)" <joel(a)joelfernandes.org> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> --- mm/madvise.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) --- a/mm/madvise.c~mm-do-not-allow-madv_pageout-for-cow-pages +++ a/mm/madvise.c @@ -335,12 +335,14 @@ static int madvise_cold_or_pageout_pte_r } page = pmd_page(orig_pmd); + + /* Do not interfere with other mappings of this page */ + if (page_mapcount(page) != 1) + goto huge_unlock; + if (next - addr != HPAGE_PMD_SIZE) { int err; - if (page_mapcount(page) != 1) - goto huge_unlock; - get_page(page); spin_unlock(ptl); lock_page(page); @@ -426,6 +428,10 @@ regular_page: continue; } + /* Do not interfere with other mappings of this page */ + if (page_mapcount(page) != 1) + continue; + VM_BUG_ON_PAGE(PageTransCompound(page), page); if (pte_young(ptent)) { _ Patches currently in -mm which might be from mhocko(a)suse.com are selftests-vm-drop-dependencies-on-page-flags-from-mlock2-tests.patch

5 years, 7 months

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[merged] mm-memcg-throttle-allocators-based-on-ancestral-memoryhigh.patch removed from -mm tree

by akpm＠linux-foundation.org

The patch titled Subject: mm, memcg: throttle allocators based on ancestral memory.high has been removed from the -mm tree. Its filename was mm-memcg-throttle-allocators-based-on-ancestral-memoryhigh.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Chris Down <chris(a)chrisdown.name> Subject: mm, memcg: throttle allocators based on ancestral memory.high Prior to this commit, we only directly check the affected cgroup's memory.high against its usage. However, it's possible that we are being reclaimed as a result of hitting an ancestor memory.high and should be penalised based on that, instead. This patch changes memory.high overage throttling to use the largest overage in its ancestors when considering how many penalty jiffies to charge. This makes sure that we penalise poorly behaving cgroups in the same way regardless of at what level of the hierarchy memory.high was breached. Link: http://lkml.kernel.org/r/8cd132f84bd7e16cdb8fde3378cdbf05ba00d387.158403614… Fixes: 0e4b01df8659 ("mm, memcg: throttle allocators when failing reclaim over memory.high") Signed-off-by: Chris Down <chris(a)chrisdown.name> Reported-by: Johannes Weiner <hannes(a)cmpxchg.org> Acked-by: Johannes Weiner <hannes(a)cmpxchg.org> Cc: Tejun Heo <tj(a)kernel.org> Cc: Michal Hocko <mhocko(a)kernel.org> Cc: Nathan Chancellor <natechancellor(a)gmail.com> Cc: Roman Gushchin <guro(a)fb.com> Cc: <stable(a)vger.kernel.org> [5.4.x+] Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> --- mm/memcontrol.c | 93 ++++++++++++++++++++++++++++------------------ 1 file changed, 58 insertions(+), 35 deletions(-) --- a/mm/memcontrol.c~mm-memcg-throttle-allocators-based-on-ancestral-memoryhigh +++ a/mm/memcontrol.c @@ -2297,28 +2297,41 @@ static void high_work_func(struct work_s #define MEMCG_DELAY_SCALING_SHIFT 14 /* - * Scheduled by try_charge() to be executed from the userland return path - * and reclaims memory over the high limit. + * Get the number of jiffies that we should penalise a mischievous cgroup which + * is exceeding its memory.high by checking both it and its ancestors. */ -void mem_cgroup_handle_over_high(void) +static unsigned long calculate_high_delay(struct mem_cgroup *memcg, + unsigned int nr_pages) { - unsigned long usage, high, clamped_high; - unsigned long pflags; - unsigned long penalty_jiffies, overage; - unsigned int nr_pages = current->memcg_nr_pages_over_high; - struct mem_cgroup *memcg; + unsigned long penalty_jiffies; + u64 max_overage = 0; - if (likely(!nr_pages)) - return; + do { + unsigned long usage, high; + u64 overage; + + usage = page_counter_read(&memcg->memory); + high = READ_ONCE(memcg->high); + + /* + * Prevent division by 0 in overage calculation by acting as if + * it was a threshold of 1 page + */ + high = max(high, 1UL); + + overage = usage - high; + overage <<= MEMCG_DELAY_PRECISION_SHIFT; + overage = div64_u64(overage, high); + + if (overage > max_overage) + max_overage = overage; + } while ((memcg = parent_mem_cgroup(memcg)) && + !mem_cgroup_is_root(memcg)); - memcg = get_mem_cgroup_from_mm(current->mm); - reclaim_high(memcg, nr_pages, GFP_KERNEL); - current->memcg_nr_pages_over_high = 0; + if (!max_overage) + return 0; /* - * memory.high is breached and reclaim is unable to keep up. Throttle - * allocators proactively to slow down excessive growth. - * * We use overage compared to memory.high to calculate the number of * jiffies to sleep (penalty_jiffies). Ideally this value should be * fairly lenient on small overages, and increasingly harsh when the @@ -2326,24 +2339,9 @@ void mem_cgroup_handle_over_high(void) * its crazy behaviour, so we exponentially increase the delay based on * overage amount. */ - - usage = page_counter_read(&memcg->memory); - high = READ_ONCE(memcg->high); - - if (usage <= high) - goto out; - - /* - * Prevent division by 0 in overage calculation by acting as if it was a - * threshold of 1 page - */ - clamped_high = max(high, 1UL); - - overage = div64_u64((u64)(usage - high) << MEMCG_DELAY_PRECISION_SHIFT, - clamped_high); - - penalty_jiffies = ((u64)overage * overage * HZ) - >> (MEMCG_DELAY_PRECISION_SHIFT + MEMCG_DELAY_SCALING_SHIFT); + penalty_jiffies = max_overage * max_overage * HZ; + penalty_jiffies >>= MEMCG_DELAY_PRECISION_SHIFT; + penalty_jiffies >>= MEMCG_DELAY_SCALING_SHIFT; /* * Factor in the task's own contribution to the overage, such that four @@ -2360,7 +2358,32 @@ void mem_cgroup_handle_over_high(void) * application moving forwards and also permit diagnostics, albeit * extremely slowly. */ - penalty_jiffies = min(penalty_jiffies, MEMCG_MAX_HIGH_DELAY_JIFFIES); + return min(penalty_jiffies, MEMCG_MAX_HIGH_DELAY_JIFFIES); +} + +/* + * Scheduled by try_charge() to be executed from the userland return path + * and reclaims memory over the high limit. + */ +void mem_cgroup_handle_over_high(void) +{ + unsigned long penalty_jiffies; + unsigned long pflags; + unsigned int nr_pages = current->memcg_nr_pages_over_high; + struct mem_cgroup *memcg; + + if (likely(!nr_pages)) + return; + + memcg = get_mem_cgroup_from_mm(current->mm); + reclaim_high(memcg, nr_pages, GFP_KERNEL); + current->memcg_nr_pages_over_high = 0; + + /* + * memory.high is breached and reclaim is unable to keep up. Throttle + * allocators proactively to slow down excessive growth. + */ + penalty_jiffies = calculate_high_delay(memcg, nr_pages); /* * Don't sleep if the amount of jiffies this memcg owes us is so low _ Patches currently in -mm which might be from chris(a)chrisdown.name are mm-memcg-prevent-memoryhigh-load-store-tearing.patch mm-memcg-prevent-memorymax-load-tearing.patch mm-memcg-prevent-memorylow-load-store-tearing.patch mm-memcg-prevent-memorymin-load-store-tearing.patch mm-memcg-prevent-memoryswapmax-load-tearing.patch mm-memcg-prevent-mem_cgroup_protected-store-tearing.patch mm-memcg-bypass-high-reclaim-iteration-for-cgroup-hierarchy-root.patch

5 years, 7 months

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[merged] mm-memcg-fix-corruption-on-64-bit-divisor-in-memoryhigh-throttling.patch removed from -mm tree

by akpm＠linux-foundation.org

The patch titled Subject: mm, memcg: fix corruption on 64-bit divisor in memory.high throttling has been removed from the -mm tree. Its filename was mm-memcg-fix-corruption-on-64-bit-divisor-in-memoryhigh-throttling.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Chris Down <chris(a)chrisdown.name> Subject: mm, memcg: fix corruption on 64-bit divisor in memory.high throttling 0e4b01df8659 had a bunch of fixups to use the right division method. However, it seems that after all that it still wasn't right -- div_u64 takes a 32-bit divisor. The headroom is still large (2^32 pages), so on mundane systems you won't hit this, but this should definitely be fixed. Link: http://lkml.kernel.org/r/80780887060514967d414b3cd91f9a316a16ab98.158403614… Fixes: 0e4b01df8659 ("mm, memcg: throttle allocators when failing reclaim over memory.high") Signed-off-by: Chris Down <chris(a)chrisdown.name> Reported-by: Johannes Weiner <hannes(a)cmpxchg.org> Acked-by: Johannes Weiner <hannes(a)cmpxchg.org> Cc: Tejun Heo <tj(a)kernel.org> Cc: Roman Gushchin <guro(a)fb.com> Cc: Michal Hocko <mhocko(a)kernel.org> Cc: Nathan Chancellor <natechancellor(a)gmail.com> Cc: <stable(a)vger.kernel.org> [5.4.x+] Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> --- mm/memcontrol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/mm/memcontrol.c~mm-memcg-fix-corruption-on-64-bit-divisor-in-memoryhigh-throttling +++ a/mm/memcontrol.c @@ -2339,7 +2339,7 @@ void mem_cgroup_handle_over_high(void) */ clamped_high = max(high, 1UL); - overage = div_u64((u64)(usage - high) << MEMCG_DELAY_PRECISION_SHIFT, + overage = div64_u64((u64)(usage - high) << MEMCG_DELAY_PRECISION_SHIFT, clamped_high); penalty_jiffies = ((u64)overage * overage * HZ) _ Patches currently in -mm which might be from chris(a)chrisdown.name are mm-memcg-prevent-memoryhigh-load-store-tearing.patch mm-memcg-prevent-memorymax-load-tearing.patch mm-memcg-prevent-memorylow-load-store-tearing.patch mm-memcg-prevent-memorymin-load-store-tearing.patch mm-memcg-prevent-memoryswapmax-load-tearing.patch mm-memcg-prevent-mem_cgroup_protected-store-tearing.patch mm-memcg-bypass-high-reclaim-iteration-for-cgroup-hierarchy-root.patch

5 years, 7 months

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[merged] page-flags-fix-a-crash-at-setpageerrorthp_swap.patch removed from -mm tree

by akpm＠linux-foundation.org

The patch titled Subject: page-flags: fix a crash at SetPageError(THP_SWAP) has been removed from the -mm tree. Its filename was page-flags-fix-a-crash-at-setpageerrorthp_swap.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Qian Cai <cai(a)lca.pw> Subject: page-flags: fix a crash at SetPageError(THP_SWAP) The commit bd4c82c22c36 ("mm, THP, swap: delay splitting THP after swapped out") supported writing THP to a swap device but forgot to upgrade an older commit df8c94d13c7e ("page-flags: define behavior of FS/IO-related flags on compound pages") which could trigger a crash during THP swapping out with DEBUG_VM_PGFLAGS=y, kernel BUG at include/linux/page-flags.h:317! page dumped because: VM_BUG_ON_PAGE(1 && PageCompound(page)) page:fffff3b2ec3a8000 refcount:512 mapcount:0 mapping:000000009eb0338c index:0x7f6e58200 head:fffff3b2ec3a8000 order:9 compound_mapcount:0 compound_pincount:0 anon flags: 0x45fffe0000d8454(uptodate|lru|workingset|owner_priv_1|writeback|head|reclaim|swapbacked) end_swap_bio_write() SetPageError(page) VM_BUG_ON_PAGE(1 && PageCompound(page)) <IRQ> bio_endio+0x297/0x560 dec_pending+0x218/0x430 [dm_mod] clone_endio+0xe4/0x2c0 [dm_mod] bio_endio+0x297/0x560 blk_update_request+0x201/0x920 scsi_end_request+0x6b/0x4b0 scsi_io_completion+0x509/0x7e0 scsi_finish_command+0x1ed/0x2a0 scsi_softirq_done+0x1c9/0x1d0 __blk_mqnterrupt+0xf/0x20 </IRQ> Fix by checking PF_NO_TAIL in those places instead. Link: http://lkml.kernel.org/r/20200310235846.1319-1-cai@lca.pw Fixes: bd4c82c22c36 ("mm, THP, swap: delay splitting THP after swapped out") Signed-off-by: Qian Cai <cai(a)lca.pw> Acked-by: "Huang, Ying" <ying.huang(a)intel.com> Reviewed-by: David Hildenbrand <david(a)redhat.com> Acked-by: Rafael Aquini <aquini(a)redhat.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> --- include/linux/page-flags.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/include/linux/page-flags.h~page-flags-fix-a-crash-at-setpageerrorthp_swap +++ a/include/linux/page-flags.h @@ -311,7 +311,7 @@ static inline int TestClearPage##uname(s __PAGEFLAG(Locked, locked, PF_NO_TAIL) PAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) __CLEARPAGEFLAG(Waiters, waiters, PF_ONLY_HEAD) -PAGEFLAG(Error, error, PF_NO_COMPOUND) TESTCLEARFLAG(Error, error, PF_NO_COMPOUND) +PAGEFLAG(Error, error, PF_NO_TAIL) TESTCLEARFLAG(Error, error, PF_NO_TAIL) PAGEFLAG(Referenced, referenced, PF_HEAD) TESTCLEARFLAG(Referenced, referenced, PF_HEAD) __SETPAGEFLAG(Referenced, referenced, PF_HEAD) _ Patches currently in -mm which might be from cai(a)lca.pw are mm-disable-kcsan-for-kmemleak.patch mm-swapfile-fix-data-races-in-try_to_unuse.patch kasan-detect-negative-size-in-memory-operation-function-fix.patch mm-vmscan-fix-data-races-at-kswapd_classzone_idx.patch percpu_counter-fix-a-data-race-at-vm_committed_as.patch mm-kmemleak-silence-kcsan-splats-in-checksum.patch mm-frontswap-mark-various-intentional-data-races.patch mm-page_io-mark-various-intentional-data-races.patch mm-page_io-mark-various-intentional-data-races-v2.patch mm-swap_state-mark-various-intentional-data-races.patch mm-swapfile-fix-and-annotate-various-data-races.patch mm-swapfile-fix-and-annotate-various-data-races-v2.patch mm-page_counter-fix-various-data-races-at-memsw.patch mm-memcontrol-fix-a-data-race-in-scan-count.patch mm-list_lru-fix-a-data-race-in-list_lru_count_one.patch mm-mempool-fix-a-data-race-in-mempool_free.patch mm-util-annotate-an-data-race-at-vm_committed_as.patch mm-rmap-annotate-a-data-race-at-tlb_flush_batched.patch mm-annotate-a-data-race-in-page_zonenum.patch mm-swap-annotate-data-races-for-lru_rotate_pvecs.patch

5 years, 7 months

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[merged] mm-hotplug-fix-hot-remove-failure-in-sparsememvmemmap-case.patch removed from -mm tree

by akpm＠linux-foundation.org

The patch titled Subject: mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case has been removed from the -mm tree. Its filename was mm-hotplug-fix-hot-remove-failure-in-sparsememvmemmap-case.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Baoquan He <bhe(a)redhat.com> Subject: mm/hotplug: fix hot remove failure in SPARSEMEM|!VMEMMAP case In section_deactivate(), pfn_to_page() doesn't work any more after ms->section_mem_map is resetting to NULL in SPARSEMEM|!VMEMMAP case. It caused hot remove failure: kernel BUG at mm/page_alloc.c:4806! invalid opcode: 0000 [#1] SMP PTI CPU: 3 PID: 8 Comm: kworker/u16:0 Tainted: G W 5.5.0-next-20200205+ #340 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015 Workqueue: kacpi_hotplug acpi_hotplug_work_fn RIP: 0010:free_pages+0x85/0xa0 Call Trace: __remove_pages+0x99/0xc0 arch_remove_memory+0x23/0x4d try_remove_memory+0xc8/0x130 ? walk_memory_blocks+0x72/0xa0 __remove_memory+0xa/0x11 acpi_memory_device_remove+0x72/0x100 acpi_bus_trim+0x55/0x90 acpi_device_hotplug+0x2eb/0x3d0 acpi_hotplug_work_fn+0x1a/0x30 process_one_work+0x1a7/0x370 worker_thread+0x30/0x380 ? flush_rcu_work+0x30/0x30 kthread+0x112/0x130 ? kthread_create_on_node+0x60/0x60 ret_from_fork+0x35/0x40 Let's move the ->section_mem_map resetting after depopulate_section_memmap() to fix it. [akpm(a)linux-foundation.org: remove unneeded initialization, per David] Link: http://lkml.kernel.org/r/20200307084229.28251-2-bhe@redhat.com Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") Signed-off-by: Baoquan He <bhe(a)redhat.com> Acked-by: Michal Hocko <mhocko(a)suse.com> Reviewed-by: Pankaj Gupta <pankaj.gupta.linux(a)gmail.com> Reviewed-by: David Hildenbrand <david(a)redhat.com> Cc: Wei Yang <richardw.yang(a)linux.intel.com> Cc: Oscar Salvador <osalvador(a)suse.de> Cc: Mike Rapoport <rppt(a)linux.ibm.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> --- mm/sparse.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) --- a/mm/sparse.c~mm-hotplug-fix-hot-remove-failure-in-sparsememvmemmap-case +++ a/mm/sparse.c @@ -734,6 +734,7 @@ static void section_deactivate(unsigned struct mem_section *ms = __pfn_to_section(pfn); bool section_is_early = early_section(ms); struct page *memmap = NULL; + bool empty; unsigned long *subsection_map = ms->usage ? &ms->usage->subsection_map[0] : NULL; @@ -764,7 +765,8 @@ static void section_deactivate(unsigned * For 2/ and 3/ the SPARSEMEM_VMEMMAP={y,n} cases are unified */ bitmap_xor(subsection_map, map, subsection_map, SUBSECTIONS_PER_SECTION); - if (bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION)) { + empty = bitmap_empty(subsection_map, SUBSECTIONS_PER_SECTION); + if (empty) { unsigned long section_nr = pfn_to_section_nr(pfn); /* @@ -779,13 +781,15 @@ static void section_deactivate(unsigned ms->usage = NULL; } memmap = sparse_decode_mem_map(ms->section_mem_map, section_nr); - ms->section_mem_map = (unsigned long)NULL; } if (section_is_early && memmap) free_map_bootmem(memmap); else depopulate_section_memmap(pfn, nr_pages, altmap); + + if (empty) + ms->section_mem_map = (unsigned long)NULL; } static struct page * __meminit section_activate(int nid, unsigned long pfn, _ Patches currently in -mm which might be from bhe(a)redhat.com are mm-sparsec-use-kvmalloc-kvfree-to-alloc-free-memmap-for-the-classic-sparse.patch mm-sparsec-allocate-memmap-preferring-the-given-node.patch mm-hotplug-only-respect-mem=-parameter-during-boot-stage.patch mm-sparsec-introduce-new-function-fill_subsection_map.patch mm-sparsec-introduce-a-new-function-clear_subsection_map.patch mm-sparsec-only-use-subsection-map-in-vmemmap-case.patch mm-sparsec-add-note-about-only-vmemmap-supporting-sub-section-hotplug.patch mm-sparsec-move-subsection_map-related-functions-together.patch mm-sparsec-move-subsection_map-related-functions-together-fix.patch

5 years, 7 months

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[merged] memcg-fix-null-pointer-dereference-in-__mem_cgroup_usage_unregister_event.patch removed from -mm tree

by akpm＠linux-foundation.org

The patch titled Subject: memcg: fix NULL pointer dereference in __mem_cgroup_usage_unregister_event has been removed from the -mm tree. Its filename was memcg-fix-null-pointer-dereference-in-__mem_cgroup_usage_unregister_event.patch This patch was dropped because it was merged into mainline or a subsystem tree ------------------------------------------------------ From: Chunguang Xu <brookxu(a)tencent.com> Subject: memcg: fix NULL pointer dereference in __mem_cgroup_usage_unregister_event An eventfd monitors multiple memory thresholds of the cgroup, closes them, the kernel deletes all events related to this eventfd. Before all events are deleted, another eventfd monitors the memory threshold of this cgroup, leading to a crash: [135.675108] BUG: kernel NULL pointer dereference, address: 0000000000000004 [135.675350] #PF: supervisor write access in kernel mode [135.675579] #PF: error_code(0x0002) - not-present page [135.675816] PGD 800000033058e067 P4D 800000033058e067 PUD 3355ce067 PMD 0 [135.676080] Oops: 0002 [#1] SMP PTI [135.676332] CPU: 2 PID: 14012 Comm: kworker/2:6 Kdump: loaded Not tainted 5.6.0-rc4 #3 [135.676610] Hardware name: LENOVO 20AWS01K00/20AWS01K00, BIOS GLET70WW (2.24 ) 05/21/2014 [135.676909] Workqueue: events memcg_event_remove [135.677192] RIP: 0010:__mem_cgroup_usage_unregister_event+0xb3/0x190 [135.677825] RSP: 0018:ffffb47e01c4fe18 EFLAGS: 00010202 [135.678186] RAX: 0000000000000001 RBX: ffff8bb223a8a000 RCX: 0000000000000001 [135.678548] RDX: 0000000000000001 RSI: ffff8bb22fb83540 RDI: 0000000000000001 [135.678912] RBP: ffffb47e01c4fe48 R08: 0000000000000000 R09: 0000000000000010 [135.679287] R10: 000000000000000c R11: 071c71c71c71c71c R12: ffff8bb226aba880 [135.679670] R13: ffff8bb223a8a480 R14: 0000000000000000 R15: 0000000000000000 [135.680066] FS: 0000000000000000(0000) GS:ffff8bb242680000(0000) knlGS:0000000000000000 [135.680475] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [135.680894] CR2: 0000000000000004 CR3: 000000032c29c003 CR4: 00000000001606e0 [135.681325] Call Trace: [135.681763]� memcg_event_remove+0x32/0x90 [135.682209]� process_one_work+0x172/0x380 [135.682657]� worker_thread+0x49/0x3f0 [135.683111]� kthread+0xf8/0x130 [135.683570]� ? max_active_store+0x80/0x80 [135.684034]� ? kthread_bind+0x10/0x10 [135.684506]� ret_from_fork+0x35/0x40 [135.689733] CR2: 0000000000000004 We can reproduce this problem in the following ways: 1. We create a new cgroup subdirectory and a new eventfd, and then we monitor multiple memory thresholds of the cgroup through this eventfd. 2. closing this eventfd, and __mem_cgroup_usage_unregister_event () will be called multiple times to delete all events related to this eventfd. The first time __mem_cgroup_usage_unregister_event() is called, the kernel will clear all items related to this eventfd in thresholds-> primary.Since there is currently only one eventfd, thresholds-> primary becomes empty, so the kernel will set thresholds-> primary and hresholds-> spare to NULL. If at this time, the user creates a new eventfd and monitor the memory threshold of this cgroup, kernel will re-initialize thresholds-> primary. Then when __mem_cgroup_usage_unregister_event () is called for the second time, because thresholds-> primary is not empty, the system will access thresholds-> spare, but thresholds-> spare is NULL, which will trigger a crash. In general, the longer it takes to delete all events related to this eventfd, the easier it is to trigger this problem. The solution is to check whether the thresholds associated with the eventfd has been cleared when deleting the event. If so, we do nothing. [akpm(a)linux-foundation.org: fix comment, per Kirill] Link: http://lkml.kernel.org/r/077a6f67-aefa-4591-efec-f2f3af2b0b02@gmail.com Fixes: 907860ed381a ("cgroups: make cftype.unregister_event() void-returning") Signed-off-by: Chunguang Xu <brookxu(a)tencent.com> Acked-by: Michal Hocko <mhocko(a)suse.com> Acked-by: Kirill A. Shutemov <kirill.shutemov(a)linux.intel.com> Cc: Johannes Weiner <hannes(a)cmpxchg.org> Cc: Vladimir Davydov <vdavydov.dev(a)gmail.com> Cc: <stable(a)vger.kernel.org> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> --- mm/memcontrol.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) --- a/mm/memcontrol.c~memcg-fix-null-pointer-dereference-in-__mem_cgroup_usage_unregister_event +++ a/mm/memcontrol.c @@ -4027,7 +4027,7 @@ static void __mem_cgroup_usage_unregiste struct mem_cgroup_thresholds *thresholds; struct mem_cgroup_threshold_ary *new; unsigned long usage; - int i, j, size; + int i, j, size, entries; mutex_lock(&memcg->thresholds_lock); @@ -4047,14 +4047,20 @@ static void __mem_cgroup_usage_unregiste __mem_cgroup_threshold(memcg, type == _MEMSWAP); /* Calculate new number of threshold */ - size = 0; + size = entries = 0; for (i = 0; i < thresholds->primary->size; i++) { if (thresholds->primary->entries[i].eventfd != eventfd) size++; + else + entries++; } new = thresholds->spare; + /* If no items related to eventfd have been cleared, nothing to do */ + if (!entries) + goto unlock; + /* Set thresholds array to NULL if we don't have thresholds */ if (!size) { kfree(new); _ Patches currently in -mm which might be from brookxu(a)tencent.com are

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