{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-89768", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.764Z", "datePublished": "2026-09-11T19:47:08.119Z", "dateUpdated": "2026-10-19T08:52:21.786Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:52:21.786Z" }, "descriptions": [ { "lang": "en", "value": "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." } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/backing-file.c" ], "versions": [ { "version": "5b6aa9a843205da92d860e5011a7b29062a76b8f", "lessThan": "88c927a63dc717b6d46b20fe13ea713916e49089", "status": "affected", "versionType": "git" }, { "version": "5dfcb15974e7d0f96aca278dd9f1b85df91523ef", "lessThan": "c03114634d342648bd34910aa8fb88007e92cc3c", "status": "affected", "versionType": "git" }, { "version": "6af36aeb147a06dea47c49859cd6ca5659aeb987", "lessThan": "a35cc21355734e1acb89973d9be90ca8e4c3ed2f", "status": "affected", "versionType": "git" }, { "version": "6af36aeb147a06dea47c49859cd6ca5659aeb987", "lessThan": "f2381b546e7e6a35c9fcee0d0ccb6c042a9aeb5d", "status": "affected", "versionType": "git" }, { "version": "41c5b269af8b1f0bffcab7766a793f294ae6764e", "status": "affected", "versionType": "git" }, { "version": "27e795afba0018b0ea9460dbad4bd706d1ba5ee0", "status": "affected", "versionType": "git" }, { "version": "6.12.95", "lessThan": "6.12.109", "status": "affected", "versionType": "semver" }, { "version": "6.18.38", "lessThan": "6.18.50", "status": "affected", "versionType": "semver" }, { "version": "6.6.144", "lessThan": "6.7", "status": "affected", "versionType": "semver" }, { "version": "7.0.4", "lessThan": "7.1", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/backing-file.c" ], "versions": [ { "version": "7.1", "status": "affected" }, { "version": "0", "lessThan": "7.1", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.109", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.50", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.95", "versionEndExcluding": "6.12.109" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18.38", "versionEndExcluding": "6.18.50" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.1", "versionEndExcluding": "7.2.4" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.1", "versionEndExcluding": "7.3" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.6.144" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0.4" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/88c927a63dc717b6d46b20fe13ea713916e49089" }, { "url": "https://git.kernel.org/stable/c/c03114634d342648bd34910aa8fb88007e92cc3c" }, { "url": "https://git.kernel.org/stable/c/a35cc21355734e1acb89973d9be90ca8e4c3ed2f" }, { "url": "https://git.kernel.org/stable/c/f2381b546e7e6a35c9fcee0d0ccb6c042a9aeb5d" } ], "title": "fs: fix user path of nested backing files", "x_generator": { "engine": "bippy-1.2.0" } } } }