The patch titled Subject: mm/kasan: fix KASAN poisoning in vrealloc() has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-kasan-fix-kasan-poisoning-in-vrealloc.patch
This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...
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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------------------------------------------------------ From: Andrey Ryabinin ryabinin.a.a@gmail.com Subject: mm/kasan: fix KASAN poisoning in vrealloc() Date: Tue, 13 Jan 2026 20:15:15 +0100
A KASAN warning can be triggered when vrealloc() changes the requested size to a value that is not aligned to KASAN_GRANULE_SIZE.
------------[ cut here ]------------ WARNING: CPU: 2 PID: 1 at mm/kasan/shadow.c:174 kasan_unpoison+0x40/0x48 ... pc : kasan_unpoison+0x40/0x48 lr : __kasan_unpoison_vmalloc+0x40/0x68 Call trace: kasan_unpoison+0x40/0x48 (P) vrealloc_node_align_noprof+0x200/0x320 bpf_patch_insn_data+0x90/0x2f0 convert_ctx_accesses+0x8c0/0x1158 bpf_check+0x1488/0x1900 bpf_prog_load+0xd20/0x1258 __sys_bpf+0x96c/0xdf0 __arm64_sys_bpf+0x50/0xa0 invoke_syscall+0x90/0x160
Introduce a dedicated kasan_vrealloc() helper that centralizes KASAN handling for vmalloc reallocations. The helper accounts for KASAN granule alignment when growing or shrinking an allocation and ensures that partial granules are handled correctly.
Use this helper from vrealloc_node_align_noprof() to fix poisoning logic.
Link: https://lkml.kernel.org/r/20260113191516.31015-1-ryabinin.a.a@gmail.com Fixes: d699440f58ce ("mm: fix vrealloc()'s KASAN poisoning logic") Signed-off-by: Andrey Ryabinin ryabinin.a.a@gmail.com Reported-by: Maciej ��enczykowski maze@google.com Reported-by: joonki.min@samsung-slsi.corp-partner.google.com Closes: https://lkml.kernel.org/r/CANP3RGeuRW53vukDy7WDO3FiVgu34-xVJYkfpm08oLO3odYFr... Cc: Alexander Potapenko glider@google.com Cc: Andrey Konovalov andreyknvl@gmail.com Cc: Dmitriy Vyukov dvyukov@google.com Cc: Dmitry Vyukov dvyukov@google.com Cc: Uladzislau Rezki urezki@gmail.com Cc: Vincenzo Frascino vincenzo.frascino@arm.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---
include/linux/kasan.h | 6 ++++++ mm/kasan/shadow.c | 24 ++++++++++++++++++++++++ mm/vmalloc.c | 7 ++----- 3 files changed, 32 insertions(+), 5 deletions(-)
--- a/include/linux/kasan.h~mm-kasan-fix-kasan-poisoning-in-vrealloc +++ a/include/linux/kasan.h @@ -641,6 +641,9 @@ kasan_unpoison_vmap_areas(struct vm_stru __kasan_unpoison_vmap_areas(vms, nr_vms, flags); }
+void kasan_vrealloc(const void *start, unsigned long old_size, + unsigned long new_size); + #else /* CONFIG_KASAN_VMALLOC */
static inline void kasan_populate_early_vm_area_shadow(void *start, @@ -670,6 +673,9 @@ kasan_unpoison_vmap_areas(struct vm_stru kasan_vmalloc_flags_t flags) { }
+static inline void kasan_vrealloc(const void *start, unsigned long old_size, + unsigned long new_size) { } + #endif /* CONFIG_KASAN_VMALLOC */
#if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) && \ --- a/mm/kasan/shadow.c~mm-kasan-fix-kasan-poisoning-in-vrealloc +++ a/mm/kasan/shadow.c @@ -651,6 +651,30 @@ void __kasan_poison_vmalloc(const void * kasan_poison(start, size, KASAN_VMALLOC_INVALID, false); }
+void kasan_vrealloc(const void *addr, unsigned long old_size, + unsigned long new_size) +{ + if (!kasan_enabled()) + return; + + if (new_size < old_size) { + kasan_poison_last_granule(addr, new_size); + + new_size = round_up(new_size, KASAN_GRANULE_SIZE); + old_size = round_up(old_size, KASAN_GRANULE_SIZE); + if (new_size < old_size) + __kasan_poison_vmalloc(addr + new_size, + old_size - new_size); + } else if (new_size > old_size) { + old_size = round_down(old_size, KASAN_GRANULE_SIZE); + __kasan_unpoison_vmalloc(addr + old_size, + new_size - old_size, + KASAN_VMALLOC_PROT_NORMAL | + KASAN_VMALLOC_VM_ALLOC | + KASAN_VMALLOC_KEEP_TAG); + } +} + #else /* CONFIG_KASAN_VMALLOC */
int kasan_alloc_module_shadow(void *addr, size_t size, gfp_t gfp_mask) --- a/mm/vmalloc.c~mm-kasan-fix-kasan-poisoning-in-vrealloc +++ a/mm/vmalloc.c @@ -4322,7 +4322,7 @@ void *vrealloc_node_align_noprof(const v if (want_init_on_free() || want_init_on_alloc(flags)) memset((void *)p + size, 0, old_size - size); vm->requested_size = size; - kasan_poison_vmalloc(p + size, old_size - size); + kasan_vrealloc(p, old_size, size); return (void *)p; }
@@ -4330,16 +4330,13 @@ 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_VMALLOC_VM_ALLOC | - KASAN_VMALLOC_KEEP_TAG); /* * No need to zero memory here, as unused memory will have * already been zeroed at initial allocation time or during * realloc shrink time. */ vm->requested_size = size; + kasan_vrealloc(p, old_size, size); return (void *)p; }
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Patches currently in -mm which might be from ryabinin.a.a@gmail.com are
mm-kasan-fix-kasan-poisoning-in-vrealloc.patch