{"id":"CVE-2026-99174","revision":"ba143cbeb25449c0b58347744a572818","records":[{"revision":"ba143cbeb25449c0b58347744a572818","observedAt":"2026-10-30T13:45:33.454+00:00","statement":{"source":"cve-program","id":"CVE-2026-99174","aliases":[],"title":"ext4: free the sbi after a grace period","description":"In the Linux kernel, the following vulnerability has been resolved:\n\next4: free the sbi after a grace period\n\next4_get_link() follows a symlink that keeps its target in a data block\nin rcu pathwalk mode with ext4_getblk(EXT4_GET_BLOCKS_CACHED_NOWAIT).\nThat reads s_mount_state in the ASSERT() of ext4_getblk() and again in\next4_es_lookup_extent(), and the lookup bumps the extent status hit or\nmiss counter, all through sb->s_fs_info.\n\next4_put_super() destroys those counters, clears sb->s_fs_info and frees\nthe sbi without waiting for a grace period. A pathwalk that is still in\next4_get_link() when the last reference to the mount goes away then\ndereferences a NULL s_fs_info, the freed sbi or the destroyed percpu\ncounters.\n\nWith a pathwalk held up in ext4_get_link() while the last reference\ngoes away:\n\n KASAN: null-ptr-deref in range [0x00000000000000a8-0x00000000000000af]\n RIP: 0010:ext4_getblk+0xf0/0x640\n Call Trace:\n \n ext4_get_link+0x26c/0x410\n pick_link+0xf96/0x1780\n step_into_slowpath+0x9b8/0x1250\n path_lookupat+0x484/0xb00\n filename_lookup+0x1f1/0x5b0\n vfs_statx+0xd7/0x3b0\n vfs_fstatat+0x4d/0x90\n __do_sys_newfstatat+0xa0/0x100\n do_syscall_64+0x10e/0x5e0\n entry_SYSCALL_64_after_hwframe+0x77/0x7f\n\nSo far that has been hard to hit. umount(2) waits for a grace period in\nnamespace_unlock() before it drops the mount, so only a mount whose last\nreference goes away elsewhere, like the close of a file or a chdir out of\na lazily unmounted directory, can race a walker.\n\nKeep sb->s_fs_info and free the sbi together with the extent status\ncounters after a grace period. Split the counters out of\next4_es_unregister_shrinker() for that. The shrinker still gets wasted\nin ext4_put_super(), the counters go with the sbi.","state":0,"publishedAt":"2026-10-28T10:35:28.758+00:00","modifiedAt":"2026-10-30T12:42:37.969+00:00","affected":[{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"unaffected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"fs/ext4/ext4.h\",\n \"fs/ext4/extents-test.c\",\n \"fs/ext4/extents.c\",\n \"fs/ext4/extents_status.c\",\n \"fs/ext4/extents_status.h\",\n \"fs/ext4/super.c\"\n ],\n \"versions\": [\n {\n \"version\": \"6493792d3299b3e33f887ef8a150099d271faf9c\",\n \"lessThan\": \"cf3bd5824c985b350d150bcd76698ee5e993fcba\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"6493792d3299b3e33f887ef8a150099d271faf9c\",\n \"lessThan\": \"b4b0598fad51a978fcbda9d55eef6b5bd3cbe7d8\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"6493792d3299b3e33f887ef8a150099d271faf9c\",\n \"lessThan\": \"4ce0e27ea610663a9cdc04e3bca38559147428d4\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"6493792d3299b3e33f887ef8a150099d271faf9c\",\n \"lessThan\": \"80d5db1686b05fad6f384be017714297d828a714\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"6493792d3299b3e33f887ef8a150099d271faf9c\",\n \"lessThan\": \"87d29b8b849738d52fe820d495fa0aa2d5a1ec82\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"6493792d3299b3e33f887ef8a150099d271faf9c\",\n \"lessThan\": \"c17b44266a1f9fcb49b894d4611d1254bf1aa313\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n }\n ]\n }"},{"ecosystem":"Vendor product","name":"Linux","ranges":[],"versions":[],"rawVersionEvidence":"{\n \"product\": \"Linux\",\n \"vendor\": \"Linux\",\n \"defaultStatus\": \"affected\",\n \"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\",\n \"programFiles\": [\n \"fs/ext4/ext4.h\",\n \"fs/ext4/extents-test.c\",\n \"fs/ext4/extents.c\",\n \"fs/ext4/extents_status.c\",\n \"fs/ext4/extents_status.h\",\n \"fs/ext4/super.c\"\n ],\n \"versions\": [\n {\n \"version\": \"5.19\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"5.19\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.1.191\",\n \"lessThanOrEqual\": \"6.1.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.161\",\n \"lessThanOrEqual\": \"6.6.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.115\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.59\",\n \"lessThanOrEqual\": \"6.18.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.2.13\",\n \"lessThanOrEqual\": \"7.2.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.3\",\n \"lessThanOrEqual\": \"*\",\n \"status\": \"unaffected\",\n \"versionType\": \"original_commit_for_fix\"\n }\n ]\n }"}],"metrics":[],"references":["https://git.kernel.org/stable/c/cf3bd5824c985b350d150bcd76698ee5e993fcba","https://git.kernel.org/stable/c/b4b0598fad51a978fcbda9d55eef6b5bd3cbe7d8","https://git.kernel.org/stable/c/4ce0e27ea610663a9cdc04e3bca38559147428d4","https://git.kernel.org/stable/c/80d5db1686b05fad6f384be017714297d828a714","https://git.kernel.org/stable/c/87d29b8b849738d52fe820d495fa0aa2d5a1ec82","https://git.kernel.org/stable/c/c17b44266a1f9fcb49b894d4611d1254bf1aa313"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-99174","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-99174","identifiers":["CVE-2026-99174"]},"retained":false,"historicalAffected":[]}],"coverage":[]}