{"id":"CVE-2026-98543","state":"PUBLISHED","title":"bpf: fs/xattr: don't assume the inode is locked in path_unlink/path_rmdir","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: fs/xattr: don't assume the inode is locked in path_unlink/path_rmdir\n\nbpf_lsm_has_d_inode_locked() makes the verifier rewrite\nbpf_[set|remove]_dentry_xattr() to the _locked variants, which assume\nthat the caller already holds the inode's i_rwsem.  The path_unlink and\npath_rmdir hooks are listed, but security_path_unlink() and\nsecurity_path_rmdir() run before vfs_unlink()/vfs_rmdir() take the\nvictim inode's i_rwsem, so a sleepable BPF LSM program attached to\neither hook mutates the victim's xattrs without the lock held.\n\nDrop the two path hooks from d_inode_locked_hooks so that the verifier\nkeeps the locking bpf_[set|remove]_dentry_xattr() variants, which take\nthe lock themselves.","publishedAt":"2026-10-18T15:18:10.823Z","updatedAt":"2026-10-24T14:09:20.159Z","severity":{"score":7.3,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"56467292794b800164df20c076c409ac548e56ec","status":"affected","lessThan":"7504b677c4370c9e4b153c553ff8831c093b1ff6","versionType":"git"},{"version":"56467292794b800164df20c076c409ac548e56ec","status":"affected","lessThan":"640d37fbd34d03af727dbc567f48c0203d1de6b4","versionType":"git"},{"version":"56467292794b800164df20c076c409ac548e56ec","status":"affected","lessThan":"35d442ed1f86465e49df3119fb898f985186db13","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/bpf_fs_kfuncs.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"6.18.55","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.9","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/bpf_fs_kfuncs.c"]}],"references":["https://git.kernel.org/stable/c/7504b677c4370c9e4b153c553ff8831c093b1ff6","https://git.kernel.org/stable/c/640d37fbd34d03af727dbc567f48c0203d1de6b4","https://git.kernel.org/stable/c/35d442ed1f86465e49df3119fb898f985186db13"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98543.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98543","state":"PUBLISHED","datePublished":"2026-10-18T15:18:10.823Z","dateUpdated":"2026-10-24T14:09:20.159Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.356Z"},"containers":{"cna":{"title":"bpf: fs/xattr: don't assume the inode is locked in path_unlink/path_rmdir","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: fs/xattr: don't assume the inode is locked in path_unlink/path_rmdir\n\nbpf_lsm_has_d_inode_locked() makes the verifier rewrite\nbpf_[set|remove]_dentry_xattr() to the _locked variants, which assume\nthat the caller already holds the inode's i_rwsem.  The path_unlink and\npath_rmdir hooks are listed, but security_path_unlink() and\nsecurity_path_rmdir() run before vfs_unlink()/vfs_rmdir() take the\nvictim inode's i_rwsem, so a sleepable BPF LSM program attached to\neither hook mutates the victim's xattrs without the lock held.\n\nDrop the two path hooks from d_inode_locked_hooks so that the verifier\nkeeps the locking bpf_[set|remove]_dentry_xattr() variants, which take\nthe lock themselves."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"56467292794b800164df20c076c409ac548e56ec","status":"affected","lessThan":"7504b677c4370c9e4b153c553ff8831c093b1ff6","versionType":"git"},{"version":"56467292794b800164df20c076c409ac548e56ec","status":"affected","lessThan":"640d37fbd34d03af727dbc567f48c0203d1de6b4","versionType":"git"},{"version":"56467292794b800164df20c076c409ac548e56ec","status":"affected","lessThan":"35d442ed1f86465e49df3119fb898f985186db13","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/bpf_fs_kfuncs.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.15","versionType":"semver"},{"version":"6.18.55","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.9","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/bpf_fs_kfuncs.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/7504b677c4370c9e4b153c553ff8831c093b1ff6"},{"url":"https://git.kernel.org/stable/c/640d37fbd34d03af727dbc567f48c0203d1de6b4"},{"url":"https://git.kernel.org/stable/c/35d442ed1f86465e49df3119fb898f985186db13"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:H","baseScore":7.3,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - unlink(2)/unlinkat(2)/rmdir(2) reach filename_unlinkat()/filename_rmdir() -> security_path_unlink()/security_path_rmdir() -> bpf_lsm_path_*(); vulnerable bpf_lsm_has_d_inode_locked() classification makes the verifier redirect bpf_[set|remove]_dentry_xattr() to _locked functions. The trigger enters locally, not via a protocol.\nAC:L - On UBIFS, one invocation deterministically fails ubifs_xattr_set()/ubifs_xattr_remove()'s inode_is_locked() assertion; for races, the attacker can unlink two hardlinks in different parents concurrently, so separate parent locks do not serialize the same victim. No condition is outside the attacker's control.\nPR:L - bpf_prog_load() gates BPF_PROG_TYPE_LSM on bpf_token_capable(CAP_BPF) and CAP_PERFMON. A delegated bpffs token makes those ns_capable(token->userns, ...) checks, so a namespace-confined non-admin can load and attach the sleepable path hook; without delegation, init-namespace capabilities are required.\nUI:N - The attacker loads and attaches the BPF LSM program, then invokes unlinkat(2) or rmdir(2) on an object it can modify; no victim must mount media, open a file, or perform another action.\nS:C - With bpffs token delegation, a task confined to the token's user namespace can run the faulty BPF LSM program in the host kernel and force a shared host UBIFS read-only, crossing the container or sandbox availability boundary.\nC:N - Neither affected helper returns filesystem or kernel data: bpf_set_dentry_xattr_locked() only passes a verifier-bounded dynptr to __vfs_setxattr(), and the remove helper has no output. The missing i_rwsem is a mutation-ordering flaw, with no demonstrated OOB read, UAF, or disclosure path.\nI:L - btrfs_setxattr() explicitly relies on the inode lock to exclude a concurrent delete between its XATTR_REPLACE lookup and insert; this bug removes that exclusion, so concurrent path_unlink hooks can recreate or lose security.bpf.* metadata. Btrfs tree locking shows no arbitrary-memory-write primitive, limiting integrity impact.\nA:H - ubifs_xattr_set(..., check_lock=true) and ubifs_xattr_remove() assert inode_is_locked(); default ASSACT_RO calls ubifs_ro_mode(), sets SB_RDONLY, and denies later writes. One path hook calling the mis-selected _locked helper can therefore make a mounted UBIFS lose write availability."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-24T14:09:20.159Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"6.18.55"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"7.2.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.15","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}