[PATCH 6.12 437/567] kasan: refactor pcpu kasan vmalloc unpoison

Greg Kroah-Hartman
2026-01-06T17:38:23Z

From: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>

commit 6f13db031e27e88213381039032a9cc061578ea6 upstream.

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.

Refactor code by reusing __kasan_unpoison_vmalloc in a new helper in
preparation for the actual fix.

Link: https://lkml.kernel.org/r/eb61d93b907e262eefcaa130261a08bcb6c5ce51.1764874575.git.m.wieczorretman@pm.me
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/kasan.h | 15 +++++++++++++++
mm/kasan/common.c | 17 +++++++++++++++++
mm/vmalloc.c | 4 +---
3 files changed, 33 insertions(+), 3 deletions(-)

--- a/include/linux/kasan.h
+++ b/include/linux/kasan.h
@@ -608,6 +608,16 @@ static __always_inline void kasan_poison
__kasan_poison_vmalloc(start, size);
}

+void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms,
+ kasan_vmalloc_flags_t flags);
+static __always_inline void
+kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms,
+ kasan_vmalloc_flags_t flags)
+{
+ if (kasan_enabled())
+ __kasan_unpoison_vmap_areas(vms, nr_vms, flags);
+}
+
#else /* CONFIG_KASAN_VMALLOC */

static inline void kasan_populate_early_vm_area_shadow(void *start,
@@ -632,6 +642,11 @@ static inline void *kasan_unpoison_vmall
static inline void kasan_poison_vmalloc(const void *start, unsigned long size)
{ }

+static __always_inline void
+kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms,
+ kasan_vmalloc_flags_t flags)
+{ }
+
#endif /* CONFIG_KASAN_VMALLOC */

#if (defined(CONFIG_KASAN_GENERIC) || defined(CONFIG_KASAN_SW_TAGS)) && \
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -28,6 +28,7 @@
#include <linux/string.h>
#include <linux/types.h>
#include <linux/bug.h>
+#include <linux/vmalloc.h>

#include "kasan.h"
#include "../slab.h"
@@ -559,3 +560,19 @@ bool __kasan_check_byte(const void *addr
}
return true;
}
+
+#ifdef CONFIG_KASAN_VMALLOC
+void __kasan_unpoison_vmap_areas(struct vm_struct **vms, int nr_vms,
+ kasan_vmalloc_flags_t flags)
+{
+ unsigned long size;
+ void *addr;
+ int area;
+
+ for (area = 0 ; area < nr_vms ; area++) {
+ size = vms[area]->size;
+ addr = vms[area]->addr;
+ vms[area]->addr = __kasan_unpoison_vmalloc(addr, size, flags);
+ }
+}
+#endif
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -4812,9 +4812,7 @@ retry:
* With hardware tag-based KASAN, marking is skipped for
* non-VM_ALLOC mappings, see __kasan_unpoison_vmalloc().
*/
- for (area = 0; area < nr_vms; area++)
- vms[area]->addr = kasan_unpoison_vmalloc(vms[area]->addr,
- vms[area]->size, KASAN_VMALLOC_PROT_NORMAL);
+ kasan_unpoison_vmap_areas(vms, nr_vms, KASAN_VMALLOC_PROT_NORMAL);

kfree(vas);
return vms;