{"id":"CVE-2026-89768","revision":"aed3243b277043ea9ee0e4cd611d2567","records":[{"revision":"aed3243b277043ea9ee0e4cd611d2567","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-89768","aliases":[],"title":"fs: fix user path of nested backing files","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nfs: fix user path of nested backing files\n\nbacking_file_open() derives the path to be stored in the new backing\nfile from user_file->f_path. This is incorrect when user_file itself\nis a backing file, which is the case for nested stacking filesystems,\ne.g. overlayfs mounts where the lowerdir of one overlayfs is the merged\ndirectory of another. Since commit def3ae83da02 (\"fs: store real path\ninstead of fake path in backing file f_path\") the f_path of a backing\nfile holds the real path of the intermediate layer, not the path that\nthe user opened.\n\nCommit 924577e4f6ca (\"ovl: Fix nested backing file paths\") fixed this\nfor such configurations by passing file_user_path() from\novl_open_realfile(). However, commit 6af36aeb147a (\"lsm: add\nbacking_file LSM hooks\") changed the first argument of\nbacking_file_open() from the user path back to the user file and\nderived the path from user_file->f_path again, silently re-introducing\nthe problem.\n\nAs a result, files mapped through a nested overlayfs show the wrong\npath in /proc//maps and in perf/ftrace mmap records. For example,\nwith two nested overlayfs mounts:\n\n mkdir -p /ovl/{lower,upper,work,merged} /ovl/nested\n echo hello > /ovl/lower/foo\n mount -t overlay overlay \\\n\t-o lowerdir=/ovl/lower,upperdir=/ovl/upper,workdir=/ovl/work \\\n\t/ovl/merged\n # at least two lowerdirs are needed when upperdir is nonexistent\n mount -t overlay overlay \\\n\t-o lowerdir=/ovl/merged:/ovl/lower /ovl/nested\n\nmapping /ovl/nested/foo shows a disconnected path instead of the user\npath:\n\n # readlink /proc/self/fd/3\n /ovl/nested/foo\n # grep foo /proc/self/maps\n 7f6e2c100000-7f6e2c101000 r--s 00000000 00:24 15813027 /foo\n\nThe bogus path is derived from the f_path of the intermediate backing\nfile, whose mount is a private clone that d_path() cannot resolve.\n\nFix this by using file_user_path(), which returns the outermost\nuser-visible path for backing files and falls back to\n&user_file->f_path for regular files. This restores the behavior of\ncommit 924577e4f6ca (\"ovl: Fix nested backing file paths\") for\noverlayfs and also fixes the same problem for the other\nbacking_file_open() callers, fuse passthrough and erofs ishare, when\ntheir user file is itself a backing file.\n\nbacking_tmpfile_open() has the same pattern but is not affected: it is\nonly called by ovl_create_tmpfile() for the upper layer, and another\noverlayfs is rejected as upperdir by the DCACHE_OP_REAL check in\novl_mount_dir_check(), so its user_file can never be a backing file.","state":0,"publishedAt":"2026-09-11T19:47:08.119+00:00","modifiedAt":"2026-10-19T08:52:21.786+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/backing-file.c\"\n ],\n \"versions\": [\n {\n \"version\": \"5b6aa9a843205da92d860e5011a7b29062a76b8f\",\n \"lessThan\": \"88c927a63dc717b6d46b20fe13ea713916e49089\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"5dfcb15974e7d0f96aca278dd9f1b85df91523ef\",\n \"lessThan\": \"c03114634d342648bd34910aa8fb88007e92cc3c\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"6af36aeb147a06dea47c49859cd6ca5659aeb987\",\n \"lessThan\": \"a35cc21355734e1acb89973d9be90ca8e4c3ed2f\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"6af36aeb147a06dea47c49859cd6ca5659aeb987\",\n \"lessThan\": \"f2381b546e7e6a35c9fcee0d0ccb6c042a9aeb5d\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"41c5b269af8b1f0bffcab7766a793f294ae6764e\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"27e795afba0018b0ea9460dbad4bd706d1ba5ee0\",\n \"status\": \"affected\",\n \"versionType\": \"git\"\n },\n {\n \"version\": \"6.12.95\",\n \"lessThan\": \"6.12.109\",\n \"status\": \"affected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.38\",\n \"lessThan\": \"6.18.50\",\n \"status\": \"affected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.6.144\",\n \"lessThan\": \"6.7\",\n \"status\": \"affected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.0.4\",\n \"lessThan\": \"7.1\",\n \"status\": \"affected\",\n \"versionType\": \"semver\"\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/backing-file.c\"\n ],\n \"versions\": [\n {\n \"version\": \"7.1\",\n \"status\": \"affected\"\n },\n {\n \"version\": \"0\",\n \"lessThan\": \"7.1\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.12.109\",\n \"lessThanOrEqual\": \"6.12.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"6.18.50\",\n \"lessThanOrEqual\": \"6.18.*\",\n \"status\": \"unaffected\",\n \"versionType\": \"semver\"\n },\n {\n \"version\": \"7.2.4\",\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/88c927a63dc717b6d46b20fe13ea713916e49089","https://git.kernel.org/stable/c/c03114634d342648bd34910aa8fb88007e92cc3c","https://git.kernel.org/stable/c/a35cc21355734e1acb89973d9be90ca8e4c3ed2f","https://git.kernel.org/stable/c/f2381b546e7e6a35c9fcee0d0ccb6c042a9aeb5d"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89768","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-89768","identifiers":["CVE-2026-89768"]},"retained":false,"historicalAffected":[]}],"coverage":[]}