The patch titled
Subject: kasan: slab: always reset the tag in get_freepointer_safe()
has been added to the -mm tree. Its filename is
kasan-slab-always-reset-the-tag-in-get_freepointer_safe.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/kasan-slab-always-reset-the-tag-in-get_freepointer_safe.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/kasan-slab-always-reset-the-tag-in-get_freepointer_safe.patch
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------------------------------------------------------
From: Alexander Potapenko <glider@xxxxxxxxxx>
Subject: kasan: slab: always reset the tag in get_freepointer_safe()
With CONFIG_DEBUG_PAGEALLOC enabled, the kernel should also untag the
object pointer, as done in get_freepointer().
Failing to do so reportedly leads to SLUB freelist corruptions that
manifest as boot-time crashes.
Link: https://lkml.kernel.org/r/20210514072228.534418-1-glider@xxxxxxxxxx
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Vincenzo Frascino <vincenzo.frascino@xxxxxxx>
Cc: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Elliot Berman <eberman@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/slub.c | 1 +
1 file changed, 1 insertion(+)
--- a/mm/slub.c~kasan-slab-always-reset-the-tag-in-get_freepointer_safe
+++ a/mm/slub.c
@@ -301,6 +301,7 @@ static inline void *get_freepointer_safe
if (!debug_pagealloc_enabled_static())
return get_freepointer(s, object);
+ object = kasan_reset_tag(object);
freepointer_addr = (unsigned long)object + s->offset;
copy_from_kernel_nofault(&p, (void **)freepointer_addr, sizeof(p));
return freelist_ptr(s, p, freepointer_addr);
_
Patches currently in -mm which might be from glider@xxxxxxxxxx are
kasan-slab-always-reset-the-tag-in-get_freepointer_safe.patch
printk-introduce-dump_stack_lvl.patch
kasan-use-dump_stack_lvlkern_err-to-print-stacks.patch
