As reported by Athul upstream in [1], there is a userspace regression caused
by commit 0c58a97f919c ("fuse: remove tmp folio for writebacks and internal rb
tree") where if there is a bug in a fuse server that causes the server to
never complete writeback, it will make wait_sb_inodes() wait forever, causing
sync paths to hang.
This is a resubmission of this patch [2] that was dropped from the original
series due to a buggy/malicious server still being able to hold up sync() /
the system in other ways if they wanted to, but the wait_sb_inodes() path is
particularly common and easier to hit for malfunctioning servers.
Thanks,
Joanne
[1] https://lore.kernel.org/regressions/CAJnrk1ZjQ8W8NzojsvJPRXiv9TuYPNdj8Ye7=C…
[2] https://lore.kernel.org/linux-fsdevel/20241122232359.429647-4-joannelkoong@…
Joanne Koong (2):
mm: rename AS_WRITEBACK_MAY_DEADLOCK_ON_RECLAIM to
AS_WRITEBACK_MAY_HANG
fs/writeback: skip inodes with potential writeback hang in
wait_sb_inodes()
fs/fs-writeback.c | 3 +++
fs/fuse/file.c | 2 +-
include/linux/pagemap.h | 10 +++++-----
mm/vmscan.c | 3 +--
4 files changed, 10 insertions(+), 8 deletions(-)
--
2.47.3
The patch titled
Subject: mm/kasan: fix incorrect unpoisoning in vrealloc for KASAN
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Jiayuan Chen <jiayuan.chen(a)linux.dev>
Subject: mm/kasan: fix incorrect unpoisoning in vrealloc for KASAN
Date: Fri, 28 Nov 2025 19:15:14 +0800
Syzkaller reported a memory out-of-bounds bug [1]. This patch fixes two
issues:
1. In vrealloc, we were missing the KASAN_VMALLOC_VM_ALLOC flag when
unpoisoning the extended region. This flag is required to correctly
associate the allocation with KASAN's vmalloc tracking.
Note: In contrast, vzalloc (via __vmalloc_node_range_noprof) explicitly
sets KASAN_VMALLOC_VM_ALLOC and calls kasan_unpoison_vmalloc() with it.
vrealloc must behave consistently ��� especially when reusing existing
vmalloc regions ��� to ensure KASAN can track allocations correctly.
2. When vrealloc reuses an existing vmalloc region (without allocating new
pages), KASAN previously generated a new tag, which broke tag-based
memory access tracking. We now add a 'reuse_tag' parameter to
__kasan_unpoison_vmalloc() to preserve the original tag in such cases.
A new helper kasan_unpoison_vralloc() is introduced to handle this reuse
scenario, ensuring consistent tag behavior during reallocation.
Link: https://lkml.kernel.org/r/20251128111516.244497-1-jiayuan.chen@linux.dev
Link: https://syzkaller.appspot.com/bug?extid=997752115a851cb0cf36 [1]
Fixes: a0309faf1cb0 ("mm: vmalloc: support more granular vrealloc() sizing")
Signed-off-by: Jiayuan Chen <jiayuan.chen(a)linux.dev>
Reported-by: syzbot+997752115a851cb0cf36(a)syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/68e243a2.050a0220.1696c6.007d.GAE@google.com/T/
Cc: Alexander Potapenko <glider(a)google.com>
Cc: Andrey Konovalov <andreyknvl(a)gmail.com>
Cc: Andrey Ryabinin <ryabinin.a.a(a)gmail.com>
Cc: Danilo Krummrich <dakr(a)kernel.org>
Cc: Dmitriy Vyukov <dvyukov(a)google.com>
Cc: Kees Cook <kees(a)kernel.org>
Cc: "Uladzislau Rezki (Sony)" <urezki(a)gmail.com>
Cc: Vincenzo Frascino <vincenzo.frascino(a)arm.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
include/linux/kasan.h | 21 +++++++++++++++++++--
mm/kasan/hw_tags.c | 4 ++--
mm/kasan/shadow.c | 6 ++++--
mm/vmalloc.c | 4 ++--
4 files changed, 27 insertions(+), 8 deletions(-)
--- a/include/linux/kasan.h~mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan
+++ a/include/linux/kasan.h
@@ -596,13 +596,23 @@ static inline void kasan_release_vmalloc
#endif /* CONFIG_KASAN_GENERIC || CONFIG_KASAN_SW_TAGS */
void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
- kasan_vmalloc_flags_t flags);
+ kasan_vmalloc_flags_t flags, bool reuse_tag);
+
+static __always_inline void *kasan_unpoison_vrealloc(const void *start,
+ unsigned long size,
+ kasan_vmalloc_flags_t flags)
+{
+ if (kasan_enabled())
+ return __kasan_unpoison_vmalloc(start, size, flags, true);
+ return (void *)start;
+}
+
static __always_inline void *kasan_unpoison_vmalloc(const void *start,
unsigned long size,
kasan_vmalloc_flags_t flags)
{
if (kasan_enabled())
- return __kasan_unpoison_vmalloc(start, size, flags);
+ return __kasan_unpoison_vmalloc(start, size, flags, false);
return (void *)start;
}
@@ -629,6 +639,13 @@ static inline void kasan_release_vmalloc
unsigned long free_region_end,
unsigned long flags) { }
+static inline void *kasan_unpoison_vrealloc(const void *start,
+ unsigned long size,
+ kasan_vmalloc_flags_t flags)
+{
+ return (void *)start;
+}
+
static inline void *kasan_unpoison_vmalloc(const void *start,
unsigned long size,
kasan_vmalloc_flags_t flags)
--- a/mm/kasan/hw_tags.c~mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan
+++ a/mm/kasan/hw_tags.c
@@ -317,7 +317,7 @@ static void init_vmalloc_pages(const voi
}
void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
- kasan_vmalloc_flags_t flags)
+ kasan_vmalloc_flags_t flags, bool reuse_tag)
{
u8 tag;
unsigned long redzone_start, redzone_size;
@@ -361,7 +361,7 @@ void *__kasan_unpoison_vmalloc(const voi
return (void *)start;
}
- tag = kasan_random_tag();
+ tag = reuse_tag ? get_tag(start) : kasan_random_tag();
start = set_tag(start, tag);
/* Unpoison and initialize memory up to size. */
--- a/mm/kasan/shadow.c~mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan
+++ a/mm/kasan/shadow.c
@@ -625,7 +625,7 @@ void kasan_release_vmalloc(unsigned long
}
void *__kasan_unpoison_vmalloc(const void *start, unsigned long size,
- kasan_vmalloc_flags_t flags)
+ kasan_vmalloc_flags_t flags, bool reuse_tag)
{
/*
* Software KASAN modes unpoison both VM_ALLOC and non-VM_ALLOC
@@ -648,7 +648,9 @@ void *__kasan_unpoison_vmalloc(const voi
!(flags & KASAN_VMALLOC_PROT_NORMAL))
return (void *)start;
- start = set_tag(start, kasan_random_tag());
+ if (!reuse_tag)
+ start = set_tag(start, kasan_random_tag());
+
kasan_unpoison(start, size, false);
return (void *)start;
}
--- a/mm/vmalloc.c~mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan
+++ a/mm/vmalloc.c
@@ -4175,8 +4175,8 @@ void *vrealloc_node_align_noprof(const v
* We already have the bytes available in the allocation; use them.
*/
if (size <= alloced_size) {
- kasan_unpoison_vmalloc(p + old_size, size - old_size,
- KASAN_VMALLOC_PROT_NORMAL);
+ kasan_unpoison_vrealloc(p, size,
+ KASAN_VMALLOC_PROT_NORMAL | KASAN_VMALLOC_VM_ALLOC);
/*
* No need to zero memory here, as unused memory will have
* already been zeroed at initial allocation time or during
_
Patches currently in -mm which might be from jiayuan.chen(a)linux.dev are
mm-kasan-fix-incorrect-unpoisoning-in-vrealloc-for-kasan.patch
mm-vmscan-skip-increasing-kswapd_failures-when-reclaim-was-boosted.patch
When ECAM is enabled, the driver skipped calling dw_pcie_iatu_setup()
before configuring ECAM iATU entries. This left IO and MEM outbound
windows unprogrammed, resulting in broken IO transactions. Additionally,
dw_pcie_config_ecam_iatu() was only called during host initialization,
so ECAM-related iATU entries were not restored after suspend/resume,
leading to failures in configuration space access.
To resolve these issues, the ECAM iATU configuration is moved into
dw_pcie_setup_rc(). At the same time, dw_pcie_iatu_setup() is invoked
when ECAM is enabled.
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru(a)oss.qualcomm.com>
---
Krishna Chaitanya Chundru (2):
PCI: dwc: Correct iATU index increment for MSG TLP region
PCI: dwc: Fix missing iATU setup when ECAM is enabled
drivers/pci/controller/dwc/pcie-designware-host.c | 37 ++++++++++++++---------
drivers/pci/controller/dwc/pcie-designware.c | 3 ++
drivers/pci/controller/dwc/pcie-designware.h | 2 +-
3 files changed, 26 insertions(+), 16 deletions(-)
---
base-commit: 3f9f0252130e7dd60d41be0802bf58f6471c691d
change-id: 20251203-ecam_io_fix-6e060fecd3b8
Best regards,
--
Krishna Chaitanya Chundru <krishna.chundru(a)oss.qualcomm.com>