The quilt patch titled Subject: kasan: unpoison vms[area] addresses with a common tag has been removed from the -mm tree. Its filename was kasan-unpoison-vms-addresses-with-a-common-tag.patch
This patch was dropped because it was merged into the mm-hotfixes-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
------------------------------------------------------ From: Maciej Wieczor-Retman maciej.wieczor-retman@intel.com Subject: kasan: unpoison vms[area] addresses with a common tag Date: Thu, 04 Dec 2025 19:00:11 +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.
Use the new vmalloc flag that disables random tag assignment in __kasan_unpoison_vmalloc() - pass the same random tag to all the vm_structs by tagging the pointers before they go inside __kasan_unpoison_vmalloc(). Assigning a common tag resolves the pcpu chunk address mismatch.
[akpm@linux-foundation.org: use WARN_ON_ONCE(), per Andrey] Link: https://lkml.kernel.org/r/CA+fCnZeuGdKSEm11oGT6FS71_vGq1vjq-xY36kxVdFvwmag2Z... [maciej.wieczor-retman@intel.com: remove unneeded pr_warn()] Link: https://lkml.kernel.org/r/919897daaaa3c982a27762a2ee038769ad033991.176494539... Link: https://lkml.kernel.org/r/873821114a9f722ffb5d6702b94782e902883fdf.176487457... Fixes: 1d96320f8d53 ("kasan, vmalloc: add vmalloc tagging for SW_TAGS") Signed-off-by: Maciej Wieczor-Retman maciej.wieczor-retman@intel.com Reviewed-by: Andrey Konovalov andreyknvl@gmail.com Cc: Alexander Potapenko glider@google.com Cc: Andrey Ryabinin ryabinin.a.a@gmail.com Cc: Danilo Krummrich dakr@kernel.org Cc: Dmitriy Vyukov dvyukov@google.com Cc: Jiayuan Chen jiayuan.chen@linux.dev Cc: Kees Cook kees@kernel.org 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 | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-)
--- a/mm/kasan/common.c~kasan-unpoison-vms-addresses-with-a-common-tag +++ a/mm/kasan/common.c @@ -584,11 +584,26 @@ void __kasan_unpoison_vmap_areas(struct unsigned long size; void *addr; int area; + u8 tag;
- for (area = 0 ; area < nr_vms ; area++) { + /* + * If KASAN_VMALLOC_KEEP_TAG was set at this point, all vms[] pointers + * would be unpoisoned with the KASAN_TAG_KERNEL which would disable + * KASAN checks down the line. + */ + if (WARN_ON_ONCE(flags & KASAN_VMALLOC_KEEP_TAG)) + return; + + size = vms[0]->size; + addr = vms[0]->addr; + vms[0]->addr = __kasan_unpoison_vmalloc(addr, size, flags); + tag = get_tag(vms[0]->addr); + + for (area = 1 ; area < nr_vms ; area++) { size = vms[area]->size; - addr = vms[area]->addr; - vms[area]->addr = __kasan_unpoison_vmalloc(addr, size, flags); + addr = set_tag(vms[area]->addr, tag); + vms[area]->addr = + __kasan_unpoison_vmalloc(addr, size, flags | KASAN_VMALLOC_KEEP_TAG); } } #endif _
Patches currently in -mm which might be from maciej.wieczor-retman@intel.com are