March 2023 - Linux-stable-mirror

[PATCH AUTOSEL 5.15 1/6] tracing: Add NULL checks for buffer in ring_buffer_free_read_page()

by Sasha Levin

From: Jia-Ju Bai <baijiaju1990(a)gmail.com> [ Upstream commit 3e4272b9954094907f16861199728f14002fcaf6 ] In a previous commit 7433632c9ff6, buffer, buffer->buffers and buffer->buffers[cpu] in ring_buffer_wake_waiters() can be NULL, and thus the related checks are added. However, in the same call stack, these variables are also used in ring_buffer_free_read_page(): tracing_buffers_release() ring_buffer_wake_waiters(iter->array_buffer->buffer) cpu_buffer = buffer->buffers[cpu] -> Add checks by previous commit ring_buffer_free_read_page(iter->array_buffer->buffer) cpu_buffer = buffer->buffers[cpu] -> No check Thus, to avod possible null-pointer derefernces, the related checks should be added. These results are reported by a static tool designed by myself. Link: https://lkml.kernel.org/r/20230113125501.760324-1-baijiaju1990@gmail.com Reported-by: TOTE Robot <oslab(a)tsinghua.edu.cn> Signed-off-by: Jia-Ju Bai <baijiaju1990(a)gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt(a)goodmis.org> Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- kernel/trace/ring_buffer.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index ffc8696e67467..41ed07e2cbc05 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -5568,11 +5568,16 @@ EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page); */ void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, void *data) { - struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; + struct ring_buffer_per_cpu *cpu_buffer; struct buffer_data_page *bpage = data; struct page *page = virt_to_page(bpage); unsigned long flags; + if (!buffer || !buffer->buffers || !buffer->buffers[cpu]) + return; + + cpu_buffer = buffer->buffers[cpu]; + /* If the page is still in use someplace else, we can't reuse it */ if (page_ref_count(page) > 1) goto out; -- 2.39.2

2 years, 9 months

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[PATCH AUTOSEL 6.1 1/6] tracing: Add NULL checks for buffer in ring_buffer_free_read_page()

by Sasha Levin

From: Jia-Ju Bai <baijiaju1990(a)gmail.com> [ Upstream commit 3e4272b9954094907f16861199728f14002fcaf6 ] In a previous commit 7433632c9ff6, buffer, buffer->buffers and buffer->buffers[cpu] in ring_buffer_wake_waiters() can be NULL, and thus the related checks are added. However, in the same call stack, these variables are also used in ring_buffer_free_read_page(): tracing_buffers_release() ring_buffer_wake_waiters(iter->array_buffer->buffer) cpu_buffer = buffer->buffers[cpu] -> Add checks by previous commit ring_buffer_free_read_page(iter->array_buffer->buffer) cpu_buffer = buffer->buffers[cpu] -> No check Thus, to avod possible null-pointer derefernces, the related checks should be added. These results are reported by a static tool designed by myself. Link: https://lkml.kernel.org/r/20230113125501.760324-1-baijiaju1990@gmail.com Reported-by: TOTE Robot <oslab(a)tsinghua.edu.cn> Signed-off-by: Jia-Ju Bai <baijiaju1990(a)gmail.com> Signed-off-by: Steven Rostedt (Google) <rostedt(a)goodmis.org> Signed-off-by: Sasha Levin <sashal(a)kernel.org> --- kernel/trace/ring_buffer.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index b21bf14bae9bd..2a5856ac25ebe 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -5610,11 +5610,16 @@ EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page); */ void ring_buffer_free_read_page(struct trace_buffer *buffer, int cpu, void *data) { - struct ring_buffer_per_cpu *cpu_buffer = buffer->buffers[cpu]; + struct ring_buffer_per_cpu *cpu_buffer; struct buffer_data_page *bpage = data; struct page *page = virt_to_page(bpage); unsigned long flags; + if (!buffer || !buffer->buffers || !buffer->buffers[cpu]) + return; + + cpu_buffer = buffer->buffers[cpu]; + /* If the page is still in use someplace else, we can't reuse it */ if (page_ref_count(page) > 1) goto out; -- 2.39.2

2 years, 9 months

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[PATCH 5.10 2/3] kexec: turn all kexec_mutex acquisitions into trylocks

by wenyang.linux＠foxmail.com

From: Valentin Schneider <vschneid(a)redhat.com> commit 7bb5da0d490b2d836c5218f5186ee588d2145310 upstream. Patch series "kexec, panic: Making crash_kexec() NMI safe", v4. This patch (of 2): Most acquistions of kexec_mutex are done via mutex_trylock() - those were a direct "translation" from: 8c5a1cf0ad3a ("kexec: use a mutex for locking rather than xchg()") there have however been two additions since then that use mutex_lock(): crash_get_memory_size() and crash_shrink_memory(). A later commit will replace said mutex with an atomic variable, and locking operations will become atomic_cmpxchg(). Rather than having those mutex_lock() become while (atomic_cmpxchg(&lock, 0, 1)), turn them into trylocks that can return -EBUSY on acquisition failure. This does halve the printable size of the crash kernel, but that's still neighbouring 2G for 32bit kernels which should be ample enough. Link: https://lkml.kernel.org/r/20220630223258.4144112-1-vschneid@redhat.com Link: https://lkml.kernel.org/r/20220630223258.4144112-2-vschneid@redhat.com Signed-off-by: Valentin Schneider <vschneid(a)redhat.com> Cc: Arnd Bergmann <arnd(a)arndb.de> Cc: "Eric W . Biederman" <ebiederm(a)xmission.com> Cc: Juri Lelli <jlelli(a)redhat.com> Cc: Luis Claudio R. Goncalves <lgoncalv(a)redhat.com> Cc: Miaohe Lin <linmiaohe(a)huawei.com> Cc: Petr Mladek <pmladek(a)suse.com> Cc: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Baoquan He <bhe(a)redhat.com> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> Cc: stable(a)vger.kernel.org # 5.10+ Signed-off-by: Wen Yang <wenyang.linux(a)foxmail.com> --- include/linux/kexec.h | 2 +- kernel/kexec_core.c | 12 ++++++++---- kernel/ksysfs.c | 7 ++++++- 3 files changed, 15 insertions(+), 6 deletions(-) diff --git a/include/linux/kexec.h b/include/linux/kexec.h index a1f12e959bba..3c1deba496c9 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -380,8 +380,8 @@ extern note_buf_t __percpu *crash_notes; extern bool kexec_in_progress; int crash_shrink_memory(unsigned long new_size); -size_t crash_get_memory_size(void); void crash_free_reserved_phys_range(unsigned long begin, unsigned long end); +ssize_t crash_get_memory_size(void); void arch_kexec_protect_crashkres(void); void arch_kexec_unprotect_crashkres(void); diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index c589c7a9562c..e47870f30728 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -989,13 +989,16 @@ void crash_kexec(struct pt_regs *regs) } } -size_t crash_get_memory_size(void) +ssize_t crash_get_memory_size(void) { - size_t size = 0; + ssize_t size = 0; + + if (!mutex_trylock(&kexec_mutex)) + return -EBUSY; - mutex_lock(&kexec_mutex); if (crashk_res.end != crashk_res.start) size = resource_size(&crashk_res); + mutex_unlock(&kexec_mutex); return size; } @@ -1016,7 +1019,8 @@ int crash_shrink_memory(unsigned long new_size) unsigned long old_size; struct resource *ram_res; - mutex_lock(&kexec_mutex); + if (!mutex_trylock(&kexec_mutex)) + return -EBUSY; if (kexec_crash_image) { ret = -ENOENT; diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c index 35859da8bd4f..e20c19e3ba49 100644 --- a/kernel/ksysfs.c +++ b/kernel/ksysfs.c @@ -106,7 +106,12 @@ KERNEL_ATTR_RO(kexec_crash_loaded); static ssize_t kexec_crash_size_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return sprintf(buf, "%zu\n", crash_get_memory_size()); + ssize_t size = crash_get_memory_size(); + + if (size < 0) + return size; + + return sprintf(buf, "%zd\n", size); } static ssize_t kexec_crash_size_store(struct kobject *kobj, struct kobj_attribute *attr, -- 2.37.2

2 years, 9 months

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[PATCH 5.10 1/3] kexec: move locking into do_kexec_load

by wenyang.linux＠foxmail.com

From: Arnd Bergmann <arnd(a)arndb.de> commit 4b692e861619353ce069e547a67c8d0e32d9ef3d upstream. Patch series "compat: remove compat_alloc_user_space", v5. Going through compat_alloc_user_space() to convert indirect system call arguments tends to add complexity compared to handling the native and compat logic in the same code. This patch (of 6): The locking is the same between the native and compat version of sys_kexec_load(), so it can be done in the common implementation to reduce duplication. Link: https://lkml.kernel.org/r/20210727144859.4150043-1-arnd@kernel.org Link: https://lkml.kernel.org/r/20210727144859.4150043-2-arnd@kernel.org Signed-off-by: Arnd Bergmann <arnd(a)arndb.de> Co-developed-by: Eric Biederman <ebiederm(a)xmission.com> Co-developed-by: Christoph Hellwig <hch(a)infradead.org> Acked-by: "Eric W. Biederman" <ebiederm(a)xmission.com> Cc: Catalin Marinas <catalin.marinas(a)arm.com> Cc: Will Deacon <will(a)kernel.org> Cc: Thomas Bogendoerfer <tsbogend(a)alpha.franken.de> Cc: "James E.J. Bottomley" <James.Bottomley(a)HansenPartnership.com> Cc: Helge Deller <deller(a)gmx.de> Cc: Michael Ellerman <mpe(a)ellerman.id.au> Cc: Benjamin Herrenschmidt <benh(a)kernel.crashing.org> Cc: Paul Mackerras <paulus(a)samba.org> Cc: Heiko Carstens <hca(a)linux.ibm.com> Cc: Vasily Gorbik <gor(a)linux.ibm.com> Cc: Christian Borntraeger <borntraeger(a)de.ibm.com> Cc: "David S. Miller" <davem(a)davemloft.net> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Ingo Molnar <mingo(a)redhat.com> Cc: Borislav Petkov <bp(a)alien8.de> Cc: "H. Peter Anvin" <hpa(a)zytor.com> Cc: Al Viro <viro(a)zeniv.linux.org.uk> Cc: Feng Tang <feng.tang(a)intel.com> Cc: Christoph Hellwig <hch(a)lst.de> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds(a)linux-foundation.org> Cc: stable(a)vger.kernel.org # 5.10+ Signed-off-by: Wen Yang <wenyang.linux(a)foxmail.com> --- kernel/kexec.c | 44 ++++++++++++++++---------------------------- 1 file changed, 16 insertions(+), 28 deletions(-) diff --git a/kernel/kexec.c b/kernel/kexec.c index c82c6c06f051..9c7aef8f4bb6 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -110,6 +110,17 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, unsigned long i; int ret; + /* + * Because we write directly to the reserved memory region when loading + * crash kernels we need a mutex here to prevent multiple crash kernels + * from attempting to load simultaneously, and to prevent a crash kernel + * from loading over the top of a in use crash kernel. + * + * KISS: always take the mutex. + */ + if (!mutex_trylock(&kexec_mutex)) + return -EBUSY; + if (flags & KEXEC_ON_CRASH) { dest_image = &kexec_crash_image; if (kexec_crash_image) @@ -121,7 +132,8 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, if (nr_segments == 0) { /* Uninstall image */ kimage_free(xchg(dest_image, NULL)); - return 0; + ret = 0; + goto out_unlock; } if (flags & KEXEC_ON_CRASH) { /* @@ -134,7 +146,7 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, ret = kimage_alloc_init(&image, entry, nr_segments, segments, flags); if (ret) - return ret; + goto out_unlock; if (flags & KEXEC_PRESERVE_CONTEXT) image->preserve_context = 1; @@ -171,6 +183,8 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, arch_kexec_protect_crashkres(); kimage_free(image); +out_unlock: + mutex_unlock(&kexec_mutex); return ret; } @@ -247,21 +261,8 @@ SYSCALL_DEFINE4(kexec_load, unsigned long, entry, unsigned long, nr_segments, ((flags & KEXEC_ARCH_MASK) != KEXEC_ARCH_DEFAULT)) return -EINVAL; - /* Because we write directly to the reserved memory - * region when loading crash kernels we need a mutex here to - * prevent multiple crash kernels from attempting to load - * simultaneously, and to prevent a crash kernel from loading - * over the top of a in use crash kernel. - * - * KISS: always take the mutex. - */ - if (!mutex_trylock(&kexec_mutex)) - return -EBUSY; - result = do_kexec_load(entry, nr_segments, segments, flags); - mutex_unlock(&kexec_mutex); - return result; } @@ -301,21 +302,8 @@ COMPAT_SYSCALL_DEFINE4(kexec_load, compat_ulong_t, entry, return -EFAULT; } - /* Because we write directly to the reserved memory - * region when loading crash kernels we need a mutex here to - * prevent multiple crash kernels from attempting to load - * simultaneously, and to prevent a crash kernel from loading - * over the top of a in use crash kernel. - * - * KISS: always take the mutex. - */ - if (!mutex_trylock(&kexec_mutex)) - return -EBUSY; - result = do_kexec_load(entry, nr_segments, ksegments, flags); - mutex_unlock(&kexec_mutex); - return result; } #endif -- 2.37.2

2 years, 9 months

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[PATCH 5.15 2/2] panic, kexec: make __crash_kexec() NMI safe

by wenyang.linux＠foxmail.com

From: Valentin Schneider <vschneid(a)redhat.com> commit 05c6257433b7212f07a7e53479a8ab038fc1666a upstream. Attempting to get a crash dump out of a debug PREEMPT_RT kernel via an NMI panic() doesn't work. The cause of that lies in the PREEMPT_RT definition of mutex_trylock(): if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES) && WARN_ON_ONCE(!in_task())) return 0; This prevents an nmi_panic() from executing the main body of __crash_kexec() which does the actual kexec into the kdump kernel. The warning and return are explained by: 6ce47fd961fa ("rtmutex: Warn if trylock is called from hard/softirq context") [...] The reasons for this are: 1) There is a potential deadlock in the slowpath 2) Another cpu which blocks on the rtmutex will boost the task which allegedly locked the rtmutex, but that cannot work because the hard/softirq context borrows the task context. Furthermore, grabbing the lock isn't NMI safe, so do away with kexec_mutex and replace it with an atomic variable. This is somewhat overzealous as *some* callsites could keep using a mutex (e.g. the sysfs-facing ones like crash_shrink_memory()), but this has the benefit of involving a single unified lock and preventing any future NMI-related surprises. Tested by triggering NMI panics via: $ echo 1 > /proc/sys/kernel/panic_on_unrecovered_nmi $ echo 1 > /proc/sys/kernel/unknown_nmi_panic $ echo 1 > /proc/sys/kernel/panic $ ipmitool power diag Link: https://lkml.kernel.org/r/20220630223258.4144112-3-vschneid@redhat.com Fixes: 6ce47fd961fa ("rtmutex: Warn if trylock is called from hard/softirq context") Signed-off-by: Valentin Schneider <vschneid(a)redhat.com> Cc: Arnd Bergmann <arnd(a)arndb.de> Cc: Baoquan He <bhe(a)redhat.com> Cc: "Eric W . Biederman" <ebiederm(a)xmission.com> Cc: Juri Lelli <jlelli(a)redhat.com> Cc: Luis Claudio R. Goncalves <lgoncalv(a)redhat.com> Cc: Miaohe Lin <linmiaohe(a)huawei.com> Cc: Petr Mladek <pmladek(a)suse.com> Cc: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de> Cc: Thomas Gleixner <tglx(a)linutronix.de> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> Cc: stable(a)vger.kernel.org # 5.15.x Signed-off-by: Wen Yang <wenyang.linux(a)foxmail.com> --- kernel/kexec.c | 11 ++++------- kernel/kexec_core.c | 20 ++++++++++---------- kernel/kexec_file.c | 4 ++-- kernel/kexec_internal.h | 15 ++++++++++++++- 4 files changed, 30 insertions(+), 20 deletions(-) diff --git a/kernel/kexec.c b/kernel/kexec.c index b5e40f069768..cb8e6e6f983c 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -93,13 +93,10 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, /* * Because we write directly to the reserved memory region when loading - * crash kernels we need a mutex here to prevent multiple crash kernels - * from attempting to load simultaneously, and to prevent a crash kernel - * from loading over the top of a in use crash kernel. - * - * KISS: always take the mutex. + * crash kernels we need a serialization here to prevent multiple crash + * kernels from attempting to load simultaneously. */ - if (!mutex_trylock(&kexec_mutex)) + if (!kexec_trylock()) return -EBUSY; if (flags & KEXEC_ON_CRASH) { @@ -165,7 +162,7 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, kimage_free(image); out_unlock: - mutex_unlock(&kexec_mutex); + kexec_unlock(); return ret; } diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index a101d2b77936..bdc2d952911c 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -46,7 +46,7 @@ #include <crypto/hash.h> #include "kexec_internal.h" -DEFINE_MUTEX(kexec_mutex); +atomic_t __kexec_lock = ATOMIC_INIT(0); /* Per cpu memory for storing cpu states in case of system crash. */ note_buf_t __percpu *crash_notes; @@ -944,7 +944,7 @@ int kexec_load_disabled; */ void __noclone __crash_kexec(struct pt_regs *regs) { - /* Take the kexec_mutex here to prevent sys_kexec_load + /* Take the kexec_lock here to prevent sys_kexec_load * running on one cpu from replacing the crash kernel * we are using after a panic on a different cpu. * @@ -952,7 +952,7 @@ void __noclone __crash_kexec(struct pt_regs *regs) * of memory the xchg(&kexec_crash_image) would be * sufficient. But since I reuse the memory... */ - if (mutex_trylock(&kexec_mutex)) { + if (kexec_trylock()) { if (kexec_crash_image) { struct pt_regs fixed_regs; @@ -961,7 +961,7 @@ void __noclone __crash_kexec(struct pt_regs *regs) machine_crash_shutdown(&fixed_regs); machine_kexec(kexec_crash_image); } - mutex_unlock(&kexec_mutex); + kexec_unlock(); } } STACK_FRAME_NON_STANDARD(__crash_kexec); @@ -993,13 +993,13 @@ ssize_t crash_get_memory_size(void) { ssize_t size = 0; - if (!mutex_trylock(&kexec_mutex)) + if (!kexec_trylock()) return -EBUSY; if (crashk_res.end != crashk_res.start) size = resource_size(&crashk_res); - mutex_unlock(&kexec_mutex); + kexec_unlock(); return size; } @@ -1019,7 +1019,7 @@ int crash_shrink_memory(unsigned long new_size) unsigned long old_size; struct resource *ram_res; - if (!mutex_trylock(&kexec_mutex)) + if (!kexec_trylock()) return -EBUSY; if (kexec_crash_image) { @@ -1058,7 +1058,7 @@ int crash_shrink_memory(unsigned long new_size) insert_resource(&iomem_resource, ram_res); unlock: - mutex_unlock(&kexec_mutex); + kexec_unlock(); return ret; } @@ -1130,7 +1130,7 @@ int kernel_kexec(void) { int error = 0; - if (!mutex_trylock(&kexec_mutex)) + if (!kexec_trylock()) return -EBUSY; if (!kexec_image) { error = -EINVAL; @@ -1206,7 +1206,7 @@ int kernel_kexec(void) #endif Unlock: - mutex_unlock(&kexec_mutex); + kexec_unlock(); return error; } diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index f7a4fd4d243f..1fb7ff690577 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -343,7 +343,7 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd, image = NULL; - if (!mutex_trylock(&kexec_mutex)) + if (!kexec_trylock()) return -EBUSY; dest_image = &kexec_image; @@ -415,7 +415,7 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd, if ((flags & KEXEC_FILE_ON_CRASH) && kexec_crash_image) arch_kexec_protect_crashkres(); - mutex_unlock(&kexec_mutex); + kexec_unlock(); kimage_free(image); return ret; } diff --git a/kernel/kexec_internal.h b/kernel/kexec_internal.h index 48aaf2ac0d0d..74da1409cd14 100644 --- a/kernel/kexec_internal.h +++ b/kernel/kexec_internal.h @@ -13,7 +13,20 @@ void kimage_terminate(struct kimage *image); int kimage_is_destination_range(struct kimage *image, unsigned long start, unsigned long end); -extern struct mutex kexec_mutex; +/* + * Whatever is used to serialize accesses to the kexec_crash_image needs to be + * NMI safe, as __crash_kexec() can happen during nmi_panic(), so here we use a + * "simple" atomic variable that is acquired with a cmpxchg(). + */ +extern atomic_t __kexec_lock; +static inline bool kexec_trylock(void) +{ + return atomic_cmpxchg_acquire(&__kexec_lock, 0, 1) == 0; +} +static inline void kexec_unlock(void) +{ + atomic_set_release(&__kexec_lock, 0); +} #ifdef CONFIG_KEXEC_FILE #include <linux/purgatory.h> -- 2.37.2

2 years, 9 months

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[PATCH 5.15 1/2] kexec: turn all kexec_mutex acquisitions into trylocks

by wenyang.linux＠foxmail.com

From: Valentin Schneider <vschneid(a)redhat.com> commit 7bb5da0d490b2d836c5218f5186ee588d2145310 upstream. Patch series "kexec, panic: Making crash_kexec() NMI safe", v4. This patch (of 2): Most acquistions of kexec_mutex are done via mutex_trylock() - those were a direct "translation" from: 8c5a1cf0ad3a ("kexec: use a mutex for locking rather than xchg()") there have however been two additions since then that use mutex_lock(): crash_get_memory_size() and crash_shrink_memory(). A later commit will replace said mutex with an atomic variable, and locking operations will become atomic_cmpxchg(). Rather than having those mutex_lock() become while (atomic_cmpxchg(&lock, 0, 1)), turn them into trylocks that can return -EBUSY on acquisition failure. This does halve the printable size of the crash kernel, but that's still neighbouring 2G for 32bit kernels which should be ample enough. Link: https://lkml.kernel.org/r/20220630223258.4144112-1-vschneid@redhat.com Link: https://lkml.kernel.org/r/20220630223258.4144112-2-vschneid@redhat.com Signed-off-by: Valentin Schneider <vschneid(a)redhat.com> Cc: Arnd Bergmann <arnd(a)arndb.de> Cc: "Eric W . Biederman" <ebiederm(a)xmission.com> Cc: Juri Lelli <jlelli(a)redhat.com> Cc: Luis Claudio R. Goncalves <lgoncalv(a)redhat.com> Cc: Miaohe Lin <linmiaohe(a)huawei.com> Cc: Petr Mladek <pmladek(a)suse.com> Cc: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Baoquan He <bhe(a)redhat.com> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> Cc: <stable(a)vger.kernel.org> # v5.15+ Signed-off-by: Wen Yang <wenyang.linux(a)foxmail.com> --- include/linux/kexec.h | 2 +- kernel/kexec_core.c | 12 ++++++++---- kernel/ksysfs.c | 7 ++++++- 3 files changed, 15 insertions(+), 6 deletions(-) diff --git a/include/linux/kexec.h b/include/linux/kexec.h index cf042d41c87b..88c289ce3039 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -390,8 +390,8 @@ extern note_buf_t __percpu *crash_notes; extern bool kexec_in_progress; int crash_shrink_memory(unsigned long new_size); -size_t crash_get_memory_size(void); void crash_free_reserved_phys_range(unsigned long begin, unsigned long end); +ssize_t crash_get_memory_size(void); void arch_kexec_protect_crashkres(void); void arch_kexec_unprotect_crashkres(void); diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index 5a5d192a89ac..a101d2b77936 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -989,13 +989,16 @@ void crash_kexec(struct pt_regs *regs) } } -size_t crash_get_memory_size(void) +ssize_t crash_get_memory_size(void) { - size_t size = 0; + ssize_t size = 0; + + if (!mutex_trylock(&kexec_mutex)) + return -EBUSY; - mutex_lock(&kexec_mutex); if (crashk_res.end != crashk_res.start) size = resource_size(&crashk_res); + mutex_unlock(&kexec_mutex); return size; } @@ -1016,7 +1019,8 @@ int crash_shrink_memory(unsigned long new_size) unsigned long old_size; struct resource *ram_res; - mutex_lock(&kexec_mutex); + if (!mutex_trylock(&kexec_mutex)) + return -EBUSY; if (kexec_crash_image) { ret = -ENOENT; diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c index 35859da8bd4f..e20c19e3ba49 100644 --- a/kernel/ksysfs.c +++ b/kernel/ksysfs.c @@ -106,7 +106,12 @@ KERNEL_ATTR_RO(kexec_crash_loaded); static ssize_t kexec_crash_size_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return sprintf(buf, "%zu\n", crash_get_memory_size()); + ssize_t size = crash_get_memory_size(); + + if (size < 0) + return size; + + return sprintf(buf, "%zd\n", size); } static ssize_t kexec_crash_size_store(struct kobject *kobj, struct kobj_attribute *attr, -- 2.37.2

2 years, 9 months

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[PATCH 3/3] panic, kexec: make __crash_kexec() NMI safe

by wenyang.linux＠foxmail.com

From: Valentin Schneider <vschneid(a)redhat.com> commit 811d581194f7412eda97acc03d17fc77824b561f upstream. Attempting to get a crash dump out of a debug PREEMPT_RT kernel via an NMI panic() doesn't work. The cause of that lies in the PREEMPT_RT definition of mutex_trylock(): if (IS_ENABLED(CONFIG_DEBUG_RT_MUTEXES) && WARN_ON_ONCE(!in_task())) return 0; This prevents an nmi_panic() from executing the main body of __crash_kexec() which does the actual kexec into the kdump kernel. The warning and return are explained by: 6ce47fd961fa ("rtmutex: Warn if trylock is called from hard/softirq context") [...] The reasons for this are: 1) There is a potential deadlock in the slowpath 2) Another cpu which blocks on the rtmutex will boost the task which allegedly locked the rtmutex, but that cannot work because the hard/softirq context borrows the task context. Furthermore, grabbing the lock isn't NMI safe, so do away with kexec_mutex and replace it with an atomic variable. This is somewhat overzealous as *some* callsites could keep using a mutex (e.g. the sysfs-facing ones like crash_shrink_memory()), but this has the benefit of involving a single unified lock and preventing any future NMI-related surprises. Tested by triggering NMI panics via: $ echo 1 > /proc/sys/kernel/panic_on_unrecovered_nmi $ echo 1 > /proc/sys/kernel/unknown_nmi_panic $ echo 1 > /proc/sys/kernel/panic $ ipmitool power diag Link: https://lkml.kernel.org/r/20220630223258.4144112-3-vschneid@redhat.com Fixes: 6ce47fd961fa ("rtmutex: Warn if trylock is called from hard/softirq context") Signed-off-by: Valentin Schneider <vschneid(a)redhat.com> Cc: Arnd Bergmann <arnd(a)arndb.de> Cc: Baoquan He <bhe(a)redhat.com> Cc: "Eric W . Biederman" <ebiederm(a)xmission.com> Cc: Juri Lelli <jlelli(a)redhat.com> Cc: Luis Claudio R. Goncalves <lgoncalv(a)redhat.com> Cc: Miaohe Lin <linmiaohe(a)huawei.com> Cc: Petr Mladek <pmladek(a)suse.com> Cc: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de> Cc: Thomas Gleixner <tglx(a)linutronix.de> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> Cc: stable(a)vger.kernel.org # 5.10+ Signed-off-by: Wen Yang <wenyang.linux(a)foxmail.com> --- kernel/kexec.c | 11 ++++------- kernel/kexec_core.c | 20 ++++++++++---------- kernel/kexec_file.c | 4 ++-- kernel/kexec_internal.h | 15 ++++++++++++++- 4 files changed, 30 insertions(+), 20 deletions(-) diff --git a/kernel/kexec.c b/kernel/kexec.c index 9c7aef8f4bb6..f0f0c6555454 100644 --- a/kernel/kexec.c +++ b/kernel/kexec.c @@ -112,13 +112,10 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, /* * Because we write directly to the reserved memory region when loading - * crash kernels we need a mutex here to prevent multiple crash kernels - * from attempting to load simultaneously, and to prevent a crash kernel - * from loading over the top of a in use crash kernel. - * - * KISS: always take the mutex. + * crash kernels we need a serialization here to prevent multiple crash + * kernels from attempting to load simultaneously. */ - if (!mutex_trylock(&kexec_mutex)) + if (!kexec_trylock()) return -EBUSY; if (flags & KEXEC_ON_CRASH) { @@ -184,7 +181,7 @@ static int do_kexec_load(unsigned long entry, unsigned long nr_segments, kimage_free(image); out_unlock: - mutex_unlock(&kexec_mutex); + kexec_unlock(); return ret; } diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index e47870f30728..7a8104d48997 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -45,7 +45,7 @@ #include <crypto/sha.h> #include "kexec_internal.h" -DEFINE_MUTEX(kexec_mutex); +atomic_t __kexec_lock = ATOMIC_INIT(0); /* Per cpu memory for storing cpu states in case of system crash. */ note_buf_t __percpu *crash_notes; @@ -943,7 +943,7 @@ int kexec_load_disabled; */ void __noclone __crash_kexec(struct pt_regs *regs) { - /* Take the kexec_mutex here to prevent sys_kexec_load + /* Take the kexec_lock here to prevent sys_kexec_load * running on one cpu from replacing the crash kernel * we are using after a panic on a different cpu. * @@ -951,7 +951,7 @@ void __noclone __crash_kexec(struct pt_regs *regs) * of memory the xchg(&kexec_crash_image) would be * sufficient. But since I reuse the memory... */ - if (mutex_trylock(&kexec_mutex)) { + if (kexec_trylock()) { if (kexec_crash_image) { struct pt_regs fixed_regs; @@ -960,7 +960,7 @@ void __noclone __crash_kexec(struct pt_regs *regs) machine_crash_shutdown(&fixed_regs); machine_kexec(kexec_crash_image); } - mutex_unlock(&kexec_mutex); + kexec_unlock(); } } STACK_FRAME_NON_STANDARD(__crash_kexec); @@ -993,13 +993,13 @@ ssize_t crash_get_memory_size(void) { ssize_t size = 0; - if (!mutex_trylock(&kexec_mutex)) + if (!kexec_trylock()) return -EBUSY; if (crashk_res.end != crashk_res.start) size = resource_size(&crashk_res); - mutex_unlock(&kexec_mutex); + kexec_unlock(); return size; } @@ -1019,7 +1019,7 @@ int crash_shrink_memory(unsigned long new_size) unsigned long old_size; struct resource *ram_res; - if (!mutex_trylock(&kexec_mutex)) + if (!kexec_trylock()) return -EBUSY; if (kexec_crash_image) { @@ -1058,7 +1058,7 @@ int crash_shrink_memory(unsigned long new_size) insert_resource(&iomem_resource, ram_res); unlock: - mutex_unlock(&kexec_mutex); + kexec_unlock(); return ret; } @@ -1130,7 +1130,7 @@ int kernel_kexec(void) { int error = 0; - if (!mutex_trylock(&kexec_mutex)) + if (!kexec_trylock()) return -EBUSY; if (!kexec_image) { error = -EINVAL; @@ -1205,7 +1205,7 @@ int kernel_kexec(void) #endif Unlock: - mutex_unlock(&kexec_mutex); + kexec_unlock(); return error; } diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c index fff11916aba3..b9c857782ada 100644 --- a/kernel/kexec_file.c +++ b/kernel/kexec_file.c @@ -343,7 +343,7 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd, image = NULL; - if (!mutex_trylock(&kexec_mutex)) + if (!kexec_trylock()) return -EBUSY; dest_image = &kexec_image; @@ -415,7 +415,7 @@ SYSCALL_DEFINE5(kexec_file_load, int, kernel_fd, int, initrd_fd, if ((flags & KEXEC_FILE_ON_CRASH) && kexec_crash_image) arch_kexec_protect_crashkres(); - mutex_unlock(&kexec_mutex); + kexec_unlock(); kimage_free(image); return ret; } diff --git a/kernel/kexec_internal.h b/kernel/kexec_internal.h index 39d30ccf8d87..49d4e3ab9c96 100644 --- a/kernel/kexec_internal.h +++ b/kernel/kexec_internal.h @@ -15,7 +15,20 @@ int kimage_is_destination_range(struct kimage *image, int machine_kexec_post_load(struct kimage *image); -extern struct mutex kexec_mutex; +/* + * Whatever is used to serialize accesses to the kexec_crash_image needs to be + * NMI safe, as __crash_kexec() can happen during nmi_panic(), so here we use a + * "simple" atomic variable that is acquired with a cmpxchg(). + */ +extern atomic_t __kexec_lock; +static inline bool kexec_trylock(void) +{ + return atomic_cmpxchg_acquire(&__kexec_lock, 0, 1) == 0; +} +static inline void kexec_unlock(void) +{ + atomic_set_release(&__kexec_lock, 0); +} #ifdef CONFIG_KEXEC_FILE #include <linux/purgatory.h> -- 2.37.2

2 years, 9 months

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[PATCH 2/3] kexec: turn all kexec_mutex acquisitions into trylocks

by wenyang.linux＠foxmail.com

From: Valentin Schneider <vschneid(a)redhat.com> commit 7bb5da0d490b2d836c5218f5186ee588d2145310 upstream. Patch series "kexec, panic: Making crash_kexec() NMI safe", v4. This patch (of 2): Most acquistions of kexec_mutex are done via mutex_trylock() - those were a direct "translation" from: 8c5a1cf0ad3a ("kexec: use a mutex for locking rather than xchg()") there have however been two additions since then that use mutex_lock(): crash_get_memory_size() and crash_shrink_memory(). A later commit will replace said mutex with an atomic variable, and locking operations will become atomic_cmpxchg(). Rather than having those mutex_lock() become while (atomic_cmpxchg(&lock, 0, 1)), turn them into trylocks that can return -EBUSY on acquisition failure. This does halve the printable size of the crash kernel, but that's still neighbouring 2G for 32bit kernels which should be ample enough. Link: https://lkml.kernel.org/r/20220630223258.4144112-1-vschneid@redhat.com Link: https://lkml.kernel.org/r/20220630223258.4144112-2-vschneid@redhat.com Signed-off-by: Valentin Schneider <vschneid(a)redhat.com> Cc: Arnd Bergmann <arnd(a)arndb.de> Cc: "Eric W . Biederman" <ebiederm(a)xmission.com> Cc: Juri Lelli <jlelli(a)redhat.com> Cc: Luis Claudio R. Goncalves <lgoncalv(a)redhat.com> Cc: Miaohe Lin <linmiaohe(a)huawei.com> Cc: Petr Mladek <pmladek(a)suse.com> Cc: Sebastian Andrzej Siewior <bigeasy(a)linutronix.de> Cc: Thomas Gleixner <tglx(a)linutronix.de> Cc: Baoquan He <bhe(a)redhat.com> Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org> Cc: stable(a)vger.kernel.org # 5.10+ Signed-off-by: Wen Yang <wenyang.linux(a)foxmail.com> --- include/linux/kexec.h | 2 +- kernel/kexec_core.c | 12 ++++++++---- kernel/ksysfs.c | 7 ++++++- 3 files changed, 15 insertions(+), 6 deletions(-) diff --git a/include/linux/kexec.h b/include/linux/kexec.h index a1f12e959bba..3c1deba496c9 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -380,8 +380,8 @@ extern note_buf_t __percpu *crash_notes; extern bool kexec_in_progress; int crash_shrink_memory(unsigned long new_size); -size_t crash_get_memory_size(void); void crash_free_reserved_phys_range(unsigned long begin, unsigned long end); +ssize_t crash_get_memory_size(void); void arch_kexec_protect_crashkres(void); void arch_kexec_unprotect_crashkres(void); diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c index c589c7a9562c..e47870f30728 100644 --- a/kernel/kexec_core.c +++ b/kernel/kexec_core.c @@ -989,13 +989,16 @@ void crash_kexec(struct pt_regs *regs) } } -size_t crash_get_memory_size(void) +ssize_t crash_get_memory_size(void) { - size_t size = 0; + ssize_t size = 0; + + if (!mutex_trylock(&kexec_mutex)) + return -EBUSY; - mutex_lock(&kexec_mutex); if (crashk_res.end != crashk_res.start) size = resource_size(&crashk_res); + mutex_unlock(&kexec_mutex); return size; } @@ -1016,7 +1019,8 @@ int crash_shrink_memory(unsigned long new_size) unsigned long old_size; struct resource *ram_res; - mutex_lock(&kexec_mutex); + if (!mutex_trylock(&kexec_mutex)) + return -EBUSY; if (kexec_crash_image) { ret = -ENOENT; diff --git a/kernel/ksysfs.c b/kernel/ksysfs.c index 35859da8bd4f..e20c19e3ba49 100644 --- a/kernel/ksysfs.c +++ b/kernel/ksysfs.c @@ -106,7 +106,12 @@ KERNEL_ATTR_RO(kexec_crash_loaded); static ssize_t kexec_crash_size_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) { - return sprintf(buf, "%zu\n", crash_get_memory_size()); + ssize_t size = crash_get_memory_size(); + + if (size < 0) + return size; + + return sprintf(buf, "%zd\n", size); } static ssize_t kexec_crash_size_store(struct kobject *kobj, struct kobj_attribute *attr, -- 2.37.2

2 years, 9 months

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[PATCH stable-queue.git] scripts/bad_stable: include instructions to fix and resubmit

by Vegard Nossum

This basically implements the suggestion from <https://lore.kernel.org/stable/46577540-6ed7-0ff5-11d5-2982cd29e92b@oracle.…>. Sample output: To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x 9f46c187e2e680ecd9de7983e4d081c3391acc76 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '<165314153515625(a)kroah.com>' --subject-prefix 'PATCH 5.15.y' HEAD^.. Signed-off-by: Vegard Nossum <vegard.nossum(a)oracle.com> --- scripts/bad_stable | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/scripts/bad_stable b/scripts/bad_stable index 03165f8212..0cd0319fb3 100755 --- a/scripts/bad_stable +++ b/scripts/bad_stable @@ -136,6 +136,15 @@ reply() echo "tree, then please email the backport, including the original git commit" echo "id to <stable(a)vger.kernel.org>." echo + echo "To reproduce the conflict and resubmit, you may use the following commands:" + echo + echo "git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-$STABLE_VERSION.y" + echo "git checkout FETCH_HEAD" + echo "git cherry-pick -x $git_id" + echo "# <resolve conflicts, build, test, etc.>" + echo "git commit -s" + echo "git send-email --to '$STABLE' --in-reply-to '$ID' --subject-prefix 'PATCH $STABLE_VERSION.y' HEAD^.." + echo echo "Possible dependencies:" echo echo "$(curl --fail --silent https://git.kernel.org/pub/scm/linux/kernel/git/sashal/deps.git/plain/v$STA…)" -- 2.35.1.46.g38062e73e0

2 years, 9 months

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[PATCH 5.10 1/2] drm/virtio: Fix NULL vs IS_ERR checking in virtio_gpu_object_shmem_init

by Ovidiu Panait

From: Miaoqian Lin <linmq006(a)gmail.com> commit c24968734abfed81c8f93dc5f44a7b7a9aecadfa upstream. Since drm_prime_pages_to_sg() function return error pointers. The drm_gem_shmem_get_sg_table() function returns error pointers too. Using IS_ERR() to check the return value to fix this. Fixes: 2f2aa13724d5 ("drm/virtio: move virtio_gpu_mem_entry initialization to new function") Signed-off-by: Miaoqian Lin <linmq006(a)gmail.com> Link: http://patchwork.freedesktop.org/patch/msgid/20220602104223.54527-1-linmq00… Signed-off-by: Gerd Hoffmann <kraxel(a)redhat.com> Signed-off-by: Ovidiu Panait <ovidiu.panait(a)windriver.com> --- drivers/gpu/drm/virtio/virtgpu_object.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c index 0c98978e2e55..d4fab3361d2c 100644 --- a/drivers/gpu/drm/virtio/virtgpu_object.c +++ b/drivers/gpu/drm/virtio/virtgpu_object.c @@ -157,9 +157,9 @@ static int virtio_gpu_object_shmem_init(struct virtio_gpu_device *vgdev, * since virtio_gpu doesn't support dma-buf import from other devices. */ shmem->pages = drm_gem_shmem_get_sg_table(&bo->base.base); - if (!shmem->pages) { + if (IS_ERR(shmem->pages)) { drm_gem_shmem_unpin(&bo->base.base); - return -EINVAL; + return PTR_ERR(shmem->pages); } if (use_dma_api) { -- 2.39.1

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