Vulnerability Details : CVE-2021-47221
In the Linux kernel, the following vulnerability has been resolved:
mm/slub: actually fix freelist pointer vs redzoning
It turns out that SLUB redzoning ("slub_debug=Z") checks from
s->object_size rather than from s->inuse (which is normally bumped to
make room for the freelist pointer), so a cache created with an object
size less than 24 would have the freelist pointer written beyond
s->object_size, causing the redzone to be corrupted by the freelist
pointer. This was very visible with "slub_debug=ZF":
BUG test (Tainted: G B ): Right Redzone overwritten
-----------------------------------------------------------------------------
INFO: 0xffff957ead1c05de-0xffff957ead1c05df @offset=1502. First byte 0x1a instead of 0xbb
INFO: Slab 0xffffef3950b47000 objects=170 used=170 fp=0x0000000000000000 flags=0x8000000000000200
INFO: Object 0xffff957ead1c05d8 @offset=1496 fp=0xffff957ead1c0620
Redzone (____ptrval____): bb bb bb bb bb bb bb bb ........
Object (____ptrval____): 00 00 00 00 00 f6 f4 a5 ........
Redzone (____ptrval____): 40 1d e8 1a aa @....
Padding (____ptrval____): 00 00 00 00 00 00 00 00 ........
Adjust the offset to stay within s->object_size.
(Note that no caches of in this size range are known to exist in the
kernel currently.)
Products affected by CVE-2021-47221
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Exploit prediction scoring system (EPSS) score for CVE-2021-47221
0.05%
Probability of exploitation activity in the next 30 days
EPSS Score History
~ 15 %
Percentile, the proportion of vulnerabilities that are scored at or less
References for CVE-2021-47221
-
https://git.kernel.org/stable/c/ce6e8bee7a3883e8008b30f5887dbb426aac6a35
mm/slub: actually fix freelist pointer vs redzoning - kernel/git/stable/linux.git - Linux kernel stable tree
-
https://git.kernel.org/stable/c/e41a49fadbc80b60b48d3c095d9e2ee7ef7c9a8e
mm/slub: actually fix freelist pointer vs redzoning - kernel/git/stable/linux.git - Linux kernel stable tree
-
https://git.kernel.org/stable/c/f6ed2357541612a13a5841b3af4dc32ed984a25f
mm/slub: actually fix freelist pointer vs redzoning - kernel/git/stable/linux.git - Linux kernel stable tree
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