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.)
OS | Version | Architecture | Package | Version | Filename |
---|---|---|---|---|---|
Debian | 12 | all | linux | < 5.10.46-1 | linux_5.10.46-1_all.deb |
Debian | 11 | all | linux | < 5.10.46-1 | linux_5.10.46-1_all.deb |
Debian | 999 | all | linux | < 5.10.46-1 | linux_5.10.46-1_all.deb |
Debian | 13 | all | linux | < 5.10.46-1 | linux_5.10.46-1_all.deb |