The patch titled
Subject: kasan: guard release_free_meta() shadow access with kasan_arch_is_ready()
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
kasan-guard-release_free_meta-shadow-access-with-kasan_arch_is_ready.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kasan-guard-release_free_meta-shadow-access-with-kasan_arch_is_ready.patch
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: Benjamin Gray <bgray@xxxxxxxxxxxxx>
Subject: kasan: guard release_free_meta() shadow access with kasan_arch_is_ready()
Date: Tue, 13 Feb 2024 14:39:58 +1100
release_free_meta() accesses the shadow directly through the path
kasan_slab_free
__kasan_slab_free
kasan_release_object_meta
release_free_meta
kasan_mem_to_shadow
There are no kasan_arch_is_ready() guards here, allowing an oops when the
shadow is not initialized. The oops can be seen on a Power8 KVM guest.
This patch adds the guard to release_free_meta(), as it's the first level
that specifically requires the shadow.
It is safe to put the guard at the start of this function, before the
stack put: only kasan_save_free_info() can initialize the saved stack,
which itself is guarded with kasan_arch_is_ready() by its caller
poison_slab_object(). If the arch becomes ready before
release_free_meta() then we will not observe KASAN_SLAB_FREE_META in the
object's shadow, so we will not put an uninitialized stack either.
Link: https://lkml.kernel.org/r/20240213033958.139383-1-bgray@xxxxxxxxxxxxx
Fixes: 63b85ac56a64 ("kasan: stop leaking stack trace handles")
Signed-off-by: Benjamin Gray <bgray@xxxxxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Andrey Ryabinin <ryabinin.a.a@xxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kasan/generic.c | 3 +++
1 file changed, 3 insertions(+)
--- a/mm/kasan/generic.c~kasan-guard-release_free_meta-shadow-access-with-kasan_arch_is_ready
+++ a/mm/kasan/generic.c
@@ -522,6 +522,9 @@ static void release_alloc_meta(struct ka
static void release_free_meta(const void *object, struct kasan_free_meta *meta)
{
+ if (!kasan_arch_is_ready())
+ return;
+
/* Check if free meta is valid. */
if (*(u8 *)kasan_mem_to_shadow(object) != KASAN_SLAB_FREE_META)
return;
_
Patches currently in -mm which might be from bgray@xxxxxxxxxxxxx are
kasan-guard-release_free_meta-shadow-access-with-kasan_arch_is_ready.patch
