The patch titled Subject: kasan: unpoison vms[area] addresses with a common tag has been added to the -mm mm-hotfixes-unstable branch. Its filename is kasan-unpoison-vms-addresses-with-a-common-tag.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: Maciej Wieczor-Retman maciej.wieczor-retman@intel.com Subject: kasan: unpoison vms[area] addresses with a common tag Date: Tue, 04 Nov 2025 14:49:48 +0000

A KASAN tag mismatch, possibly causing a kernel panic, can be observed on systems with a tag-based KASAN enabled and with multiple NUMA nodes. It was reported on arm64 and reproduced on x86. It can be explained in the following points:

1. There can be more than one virtual memory chunk. 2. Chunk's base address has a tag. 3. The base address points at the first chunk and thus inherits the tag of the first chunk. 4. The subsequent chunks will be accessed with the tag from the first chunk. 5. Thus, the subsequent chunks need to have their tag set to match that of the first chunk.

Unpoison all vm_structs after allocating them for the percpu allocator. Use the same tag to resolve the pcpu chunk address mismatch.

Link: https://lkml.kernel.org/r/cf8fe0ffcdbf54e06d9df26c8473b123c4065f02.176226702... Fixes: 1d96320f8d53 ("kasan, vmalloc: add vmalloc tagging for SW_TAGS") Signed-off-by: Maciej Wieczor-Retman maciej.wieczor-retman@intel.com Tested-by: Baoquan He bhe@redhat.com Cc: Alexander Potapenko glider@google.com Cc: Andrey Konovalov andreyknvl@gmail.com Cc: Andrey Ryabinin ryabinin.a.a@gmail.com Cc: Dmitriy Vyukov dvyukov@google.com Cc: Marco Elver elver@google.com Cc: "Uladzislau Rezki (Sony)" urezki@gmail.com Cc: Vincenzo Frascino vincenzo.frascino@arm.com Cc: stable@vger.kernel.org [6.1+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/kasan/common.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/mm/kasan/common.c~kasan-unpoison-vms-addresses-with-a-common-tag +++ a/mm/kasan/common.c @@ -584,12 +584,20 @@ bool __kasan_check_byte(const void *addr return true; }

+/* + * A tag mismatch happens when calculating per-cpu chunk addresses, because + * they all inherit the tag from vms[0]->addr, even when nr_vms is bigger + * than 1. This is a problem because all the vms[]->addr come from separate + * allocations and have different tags so while the calculated address is + * correct the tag isn't. + */ void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms) { int area;

for (area = 0 ; area < nr_vms ; area++) { kasan_poison(vms[area]->addr, vms[area]->size, - arch_kasan_get_tag(vms[area]->addr), false); + arch_kasan_get_tag(vms[0]->addr), false); + arch_kasan_set_tag(vms[area]->addr, arch_kasan_get_tag(vms[0]->addr)); } } _

Patches currently in -mm which might be from maciej.wieczor-retman@intel.com are

kasan-unpoison-pcpu-chunks-with-base-address-tag.patch kasan-unpoison-vms-addresses-with-a-common-tag.patch