Bugzilla – Bug 1224858
VUL-0: CVE-2021-47221: kernel: mm/slub: actually fix freelist pointer vs redzoning
Last modified: 2024-06-10 12:06:26 UTC
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.) References: http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-47221 https://www.cve.org/CVERecord?id=CVE-2021-47221 https://git.kernel.org/stable/c/ce6e8bee7a3883e8008b30f5887dbb426aac6a35 https://git.kernel.org/stable/c/e41a49fadbc80b60b48d3c095d9e2ee7ef7c9a8e https://git.kernel.org/stable/c/f6ed2357541612a13a5841b3af4dc32ed984a25f https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2021/CVE-2021-47221.mbox
None of SLE branches is affected because pre v5.13 trees have CONFIG_SLAB=y
All done, closing.