{"id":"CVE-2026-89767","revision":"904ee842c50f49c6945fa655af105551","records":[{"revision":"904ee842c50f49c6945fa655af105551","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-89767","aliases":[],"title":"ovl: fix double end_creating() on the casefold-mismatch path","description":"In the Linux kernel, the following vulnerability has been resolved:\n\novl: fix double end_creating() on the casefold-mismatch path\n\novl_create_real() releases the new dentry twice when the casefold\nconsistency check fails.  The S_IFDIR branch calls end_creating() and\nsets err, then falls through to the common out: label which calls\nend_creating() on the same dentry again:\n\n\tcase S_IFDIR:\n\t\tnewdentry = ovl_do_mkdir(ofs, dir, newdentry, attr->mode);\n\t\terr = PTR_ERR_OR_ZERO(newdentry);\n\t\tif (!err && ofs->casefold != ovl_dentry_casefolded(newdentry)) {\n\t\t\tpr_warn_ratelimited(...);\n\t\t\tend_creating(newdentry);\t/* first */\n\t\t\terr = -EINVAL;\n\t\t}\n\t\tbreak;\n\t...\n\tif (err)\n\t\tgoto out;\n\t...\n out:\n\tif (err) {\n\t\tend_creating(newdentry);\t/* second, same dentry */\n\t\treturn ERR_PTR(err);\n\t}\n\nend_creating() is end_dirop(), which does inode_unlock() on the parent\nand dput() on the dentry, so the parent directory's i_rwsem is unlocked\ntwice and the dentry is put twice.  The second unlock releases a lock\nthat is not held, which is what wedges every later creation under that\nparent, and the second dput() drops a reference that was never taken.\n\nThe branch was added by commit dfc7da402ccc (\"ovl: Check for casefold\nconsistency when creating new dentries\") as a bare dput(), which already\nreleased the reference twice; commit fe497f0759e0 (\"VFS: change\nvfs_mkdir() to unlock on failure.\") converted both sites to\nend_creating(), adding the double unlock.\n\nThis is reachable by an unprivileged user.  The casefold consistency of\nthe layers is validated at mount time in ovl_parse_layer(), and again on\nevery lookup in ovl_lookup_single(), but ofs->workdir is the internal\n\"work\" subdirectory created inside the user-supplied workdir, and that\nsubdirectory is not re-checked.  Marking it casefolded after the mount\ntherefore makes every ovl_create_temp() inherit the wrong state - and\nthat path reaches ovl_create_real() through ovl_start_creating_temp(),\nwhich uses start_creating() with a generated name and so never runs the\nlookup-time check.\n\n  unshare -Urm\n  mount -t tmpfs -o casefold=utf8-12.1.0 tmpfs mnt\n  mkdir -p mnt/lower/d mnt/upper mnt/work mnt/merged\n  mount -t overlay ovl -o lowerdir=mnt/lower,\\\n        upperdir=mnt/upper,workdir=mnt/work mnt/merged\n  chattr +F mnt/work/work\n  mkdir mnt/merged/d/sub\t\t# directory copy-up\n\n  overlayfs: wrong inherited casefold (work/#5)\n\nand the next copy-up blocks forever on the parent's i_rwsem:\n\n  mkdir           D  start_creating+0x65/0xb0\n                     ovl_start_creating_temp+0xb0/0xe0 [overlay]\n                     ovl_create_temp+0xa3/0x1d0 [overlay]\n                     ovl_copy_up_one+0x1f1c/0x21c0 [overlay]\n                     ovl_copy_up_flags+0xf5/0x140 [overlay]\n                     ovl_create_object+0xb7/0x220 [overlay]\n                     ovl_mkdir+0x23/0x40 [overlay]\n\nDrop the end_creating() from the branch and let out: own the cleanup,\nwhich is what every other error path in this function already does.","state":0,"publishedAt":"2026-09-11T19:47:07.353+00:00","modifiedAt":"2026-10-19T08:52:20.802+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/overlayfs/dir.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"dfc7da402ccc92d6e4b01a4778a3f15f2496b9af\",\n                            \"lessThan\": \"2fa220bc0f84597cb6de665e5b5021c5901ddf00\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"dfc7da402ccc92d6e4b01a4778a3f15f2496b9af\",\n                            \"lessThan\": \"b1aa8ab78a8e87aee9e306971465408e059f839a\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"git\"\n                        },\n                        {\n                            \"version\": \"dfc7da402ccc92d6e4b01a4778a3f15f2496b9af\",\n                            \"lessThan\": \"077ab8985ee278c3d8618182d335b0f0cd919e16\",\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/overlayfs/dir.c\"\n                    ],\n                    \"versions\": [\n                        {\n                            \"version\": \"6.18\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \"0\",\n                            \"lessThan\": \"6.18\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"6.18.51\",\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":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","score":7.8,"severity":"HIGH"}],"references":["https://git.kernel.org/stable/c/2fa220bc0f84597cb6de665e5b5021c5901ddf00","https://git.kernel.org/stable/c/b1aa8ab78a8e87aee9e306971465408e059f839a","https://git.kernel.org/stable/c/077ab8985ee278c3d8618182d335b0f0cd919e16"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-89767","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-89767","identifiers":["CVE-2026-89767"]},"retained":false,"historicalAffected":[]}],"coverage":[]}