{"id":"CVE-2021-47221","state":"PUBLISHED","title":"mm/slub: actually fix freelist pointer vs redzoning","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/slub: actually fix freelist pointer vs redzoning\n\nIt turns out that SLUB redzoning (\"slub_debug=Z\") checks from\ns->object_size rather than from s->inuse (which is normally bumped to\nmake room for the freelist pointer), so a cache created with an object\nsize less than 24 would have the freelist pointer written beyond\ns->object_size, causing the redzone to be corrupted by the freelist\npointer.  This was very visible with \"slub_debug=ZF\":\n\n  BUG test (Tainted: G    B            ): Right Redzone overwritten\n  -----------------------------------------------------------------------------\n\n  INFO: 0xffff957ead1c05de-0xffff957ead1c05df @offset=1502. First byte 0x1a instead of 0xbb\n  INFO: Slab 0xffffef3950b47000 objects=170 used=170 fp=0x0000000000000000 flags=0x8000000000000200\n  INFO: Object 0xffff957ead1c05d8 @offset=1496 fp=0xffff957ead1c0620\n\n  Redzone  (____ptrval____): bb bb bb bb bb bb bb bb               ........\n  Object   (____ptrval____): 00 00 00 00 00 f6 f4 a5               ........\n  Redzone  (____ptrval____): 40 1d e8 1a aa                        @....\n  Padding  (____ptrval____): 00 00 00 00 00 00 00 00               ........\n\nAdjust the offset to stay within s->object_size.\n\n(Note that no caches of in this size range are known to exist in the\nkernel currently.)","publishedAt":"2024-05-21T14:19:27.553Z","updatedAt":"2026-05-11T13:50:18.334Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"89b83f282d8ba380cf2124f88106c57df49c538c","status":"affected","lessThan":"f6ed2357541612a13a5841b3af4dc32ed984a25f","versionType":"git"},{"version":"89b83f282d8ba380cf2124f88106c57df49c538c","status":"affected","lessThan":"ce6e8bee7a3883e8008b30f5887dbb426aac6a35","versionType":"git"},{"version":"89b83f282d8ba380cf2124f88106c57df49c538c","status":"affected","lessThan":"e41a49fadbc80b60b48d3c095d9e2ee7ef7c9a8e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/slub.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.7","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.7","versionType":"semver"},{"version":"5.10.46","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.12.13","status":"unaffected","lessThanOrEqual":"5.12.*","versionType":"semver"},{"version":"5.13","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/slub.c"]}],"references":["https://git.kernel.org/stable/c/f6ed2357541612a13a5841b3af4dc32ed984a25f","https://git.kernel.org/stable/c/ce6e8bee7a3883e8008b30f5887dbb426aac6a35","https://git.kernel.org/stable/c/e41a49fadbc80b60b48d3c095d9e2ee7ef7c9a8e"],"weaknesses":[],"ingestedAt":"2026-10-29T19:49:19.404Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2021/47xxx/CVE-2021-47221.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2021-47221","state":"PUBLISHED","datePublished":"2024-05-21T14:19:27.553Z","dateUpdated":"2026-05-11T13:50:18.334Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2024-04-10T18:59:19.529Z"},"containers":{"cna":{"title":"mm/slub: actually fix freelist pointer vs redzoning","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/slub: actually fix freelist pointer vs redzoning\n\nIt turns out that SLUB redzoning (\"slub_debug=Z\") checks from\ns->object_size rather than from s->inuse (which is normally bumped to\nmake room for the freelist pointer), so a cache created with an object\nsize less than 24 would have the freelist pointer written beyond\ns->object_size, causing the redzone to be corrupted by the freelist\npointer.  This was very visible with \"slub_debug=ZF\":\n\n  BUG test (Tainted: G    B            ): Right Redzone overwritten\n  -----------------------------------------------------------------------------\n\n  INFO: 0xffff957ead1c05de-0xffff957ead1c05df @offset=1502. First byte 0x1a instead of 0xbb\n  INFO: Slab 0xffffef3950b47000 objects=170 used=170 fp=0x0000000000000000 flags=0x8000000000000200\n  INFO: Object 0xffff957ead1c05d8 @offset=1496 fp=0xffff957ead1c0620\n\n  Redzone  (____ptrval____): bb bb bb bb bb bb bb bb               ........\n  Object   (____ptrval____): 00 00 00 00 00 f6 f4 a5               ........\n  Redzone  (____ptrval____): 40 1d e8 1a aa                        @....\n  Padding  (____ptrval____): 00 00 00 00 00 00 00 00               ........\n\nAdjust the offset to stay within s->object_size.\n\n(Note that no caches of in this size range are known to exist in the\nkernel currently.)"}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"89b83f282d8ba380cf2124f88106c57df49c538c","status":"affected","lessThan":"f6ed2357541612a13a5841b3af4dc32ed984a25f","versionType":"git"},{"version":"89b83f282d8ba380cf2124f88106c57df49c538c","status":"affected","lessThan":"ce6e8bee7a3883e8008b30f5887dbb426aac6a35","versionType":"git"},{"version":"89b83f282d8ba380cf2124f88106c57df49c538c","status":"affected","lessThan":"e41a49fadbc80b60b48d3c095d9e2ee7ef7c9a8e","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/slub.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.7","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.7","versionType":"semver"},{"version":"5.10.46","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.12.13","status":"unaffected","lessThanOrEqual":"5.12.*","versionType":"semver"},{"version":"5.13","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/slub.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/f6ed2357541612a13a5841b3af4dc32ed984a25f"},{"url":"https://git.kernel.org/stable/c/ce6e8bee7a3883e8008b30f5887dbb426aac6a35"},{"url":"https://git.kernel.org/stable/c/e41a49fadbc80b60b48d3c095d9e2ee7ef7c9a8e"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-05-11T13:50:18.334Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"5.10.46"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"5.12.13"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.7","versionEndExcluding":"5.13"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2024-06-17T17:38:07.843861Z","id":"CVE-2021-47221","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2024-06-17T17:40:09.755Z"}},{"title":"CVE Program Container","references":[{"url":"https://git.kernel.org/stable/c/f6ed2357541612a13a5841b3af4dc32ed984a25f","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/ce6e8bee7a3883e8008b30f5887dbb426aac6a35","tags":["x_transferred"]},{"url":"https://git.kernel.org/stable/c/e41a49fadbc80b60b48d3c095d9e2ee7ef7c9a8e","tags":["x_transferred"]}],"providerMetadata":{"shortName":"CVE","orgId":"af854a3a-2127-422b-91ae-364da2661108","dateUpdated":"2024-08-04T05:32:07.427Z"}}]}}}