{"id":"DEBIAN-CVE-2026-89767","details":"In the Linux kernel, the following vulnerability has been resolved:  ovl: fix double end_creating() on the casefold-mismatch path  ovl_create_real() releases the new dentry twice when the casefold consistency check fails.  The S_IFDIR branch calls end_creating() and sets err, then falls through to the common out: label which calls end_creating() on the same dentry again:  \tcase S_IFDIR: \t\tnewdentry = ovl_do_mkdir(ofs, dir, newdentry, attr-\u003emode); \t\terr = PTR_ERR_OR_ZERO(newdentry); \t\tif (!err && ofs-\u003ecasefold != ovl_dentry_casefolded(newdentry)) { \t\t\tpr_warn_ratelimited(...); \t\t\tend_creating(newdentry);\t/* first */ \t\t\terr = -EINVAL; \t\t} \t\tbreak; \t... \tif (err) \t\tgoto out; \t...  out: \tif (err) { \t\tend_creating(newdentry);\t/* second, same dentry */ \t\treturn ERR_PTR(err); \t}  end_creating() is end_dirop(), which does inode_unlock() on the parent and dput() on the dentry, so the parent directory's i_rwsem is unlocked twice and the dentry is put twice.  The second unlock releases a lock that is not held, which is what wedges every later creation under that parent, and the second dput() drops a reference that was never taken.  The branch was added by commit dfc7da402ccc (\"ovl: Check for casefold consistency when creating new dentries\") as a bare dput(), which already released the reference twice; commit fe497f0759e0 (\"VFS: change vfs_mkdir() to unlock on failure.\") converted both sites to end_creating(), adding the double unlock.  This is reachable by an unprivileged user.  The casefold consistency of the layers is validated at mount time in ovl_parse_layer(), and again on every lookup in ovl_lookup_single(), but ofs-\u003eworkdir is the internal \"work\" subdirectory created inside the user-supplied workdir, and that subdirectory is not re-checked.  Marking it casefolded after the mount therefore makes every ovl_create_temp() inherit the wrong state - and that path reaches ovl_create_real() through ovl_start_creating_temp(), which uses start_creating() with a generated name and so never runs the lookup-time check.    unshare -Urm   mount -t tmpfs -o casefold=utf8-12.1.0 tmpfs mnt   mkdir -p mnt/lower/d mnt/upper mnt/work mnt/merged   mount -t overlay ovl -o lowerdir=mnt/lower,\\         upperdir=mnt/upper,workdir=mnt/work mnt/merged   chattr +F mnt/work/work   mkdir mnt/merged/d/sub\t\t# directory copy-up    overlayfs: wrong inherited casefold (work/#5)  and the next copy-up blocks forever on the parent's i_rwsem:    mkdir           D  start_creating+0x65/0xb0                      ovl_start_creating_temp+0xb0/0xe0 [overlay]                      ovl_create_temp+0xa3/0x1d0 [overlay]                      ovl_copy_up_one+0x1f1c/0x21c0 [overlay]                      ovl_copy_up_flags+0xf5/0x140 [overlay]                      ovl_create_object+0xb7/0x220 [overlay]                      ovl_mkdir+0x23/0x40 [overlay]  Drop the end_creating() from the branch and let out: own the cleanup, which is what every other error path in this function already does.","modified":"2026-09-23T04:01:01.582757458Z","published":"2026-09-11T20:20:07.960Z","upstream":["CVE-2026-89767"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-89767"}],"affected":[{"package":{"name":"linux","ecosystem":"Debian:14","purl":"pkg:deb/debian/linux?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.2.6-1"}]}],"versions":["6.12.100-1","6.12.101-1","6.12.105-1","6.12.107-1","6.12.38-1","6.12.41-1","6.12.43-1","6.12.43-1~bpo12+1","6.12.48-1","6.12.57-1","6.12.57-1~bpo12+1","6.12.63-1","6.12.63-1~bpo12+1","6.12.69-1","6.12.69-1~bpo12+1","6.12.73-1","6.12.73-1~bpo12+1","6.12.74-1","6.12.74-2","6.12.74-2~bpo12+1","6.12.85-1","6.12.85-1~bpo12+1","6.12.86-1","6.12.86-1~bpo12+1","6.12.88-1","6.12.88-1~bpo12+1","6.12.90-1","6.12.90-1~bpo12+1","6.12.90-2","6.12.90-2~bpo12+1","6.12.94-1","6.12.94-1~bpo12+1","6.12.95-1","6.12.95-1~bpo12+1","6.12.96-1","6.13.10-1~exp1","6.13.11-1~exp1","6.13.2-1~exp1","6.13.3-1~exp1","6.13.4-1~exp1","6.13.5-1~exp1","6.13.6-1~exp1","6.13.7-1~exp1","6.13.8-1~exp1","6.13.9-1~exp1","6.13~rc6-1~exp1","6.13~rc7-1~exp1","6.14.3-1~exp1","6.14.5-1~exp1","6.14.6-1~exp1","6.15-1~exp1","6.15.1-1~exp1","6.15.2-1~exp1","6.15.3-1~exp1","6.15.4-1~exp1","6.15.5-1~exp1","6.15.6-1~exp1","6.15~rc7-1~exp1","6.16-1~exp1","6.16.1-1~exp1","6.16.10-1","6.16.11-1","6.16.12-1","6.16.12-1~bpo13+1","6.16.12-2","6.16.3-1","6.16.3-1~bpo13+1","6.16.5-1","6.16.6-1","6.16.7-1","6.16.8-1","6.16.9-1","6.16~rc7-1~exp1","6.17.10-1","6.17.11-1","6.17.12-1","6.17.13-1","6.17.13-1~bpo13+1","6.17.2-1~exp1","6.17.5-1~exp1","6.17.6-1","6.17.7-1","6.17.7-2","6.17.8-1","6.17.8-1~bpo13+1","6.17.9-1","6.18.1-1~exp1","6.18.10-1","6.18.12-1","6.18.12-1~bpo13+1","6.18.13-1","6.18.14-1","6.18.15-1","6.18.15-1~bpo13+1","6.18.2-1~exp1","6.18.3-1","6.18.5-1","6.18.5-1~bpo13+1","6.18.8-1","6.18.9-1","6.18.9-1~bpo13+1","6.18~rc4-1~exp1","6.18~rc4-1~exp2","6.18~rc5-1~exp1","6.18~rc6-1~exp1","6.18~rc7-1~exp1","6.19-1~exp1","6.19.10-1","6.19.10-1~bpo13+1","6.19.11-1","6.19.11-1~bpo13+1","6.19.12-1","6.19.13-1","6.19.13-1~bpo13+1","6.19.14-1","6.19.14-1~bpo13+1","6.19.2-1~exp1","6.19.3-1~exp1","6.19.4-1~exp1","6.19.5-1~exp1","6.19.6-1","6.19.6-2","6.19.6-2~bpo13+1","6.19.8-1","6.19.8-1~bpo13+1","6.19~rc4-1~exp1","6.19~rc5-1~exp1","6.19~rc6-1~exp1","6.19~rc7-1~exp1","6.19~rc8-1~exp1","7.0-1~exp1","7.0.1-1~exp1","7.0.10-1","7.0.10-1~bpo13+1","7.0.12-1","7.0.12-2","7.0.12-2~bpo13+1","7.0.13-1","7.0.13-1~bpo13+1","7.0.14-1","7.0.3-1","7.0.4-1","7.0.4-1~bpo13+1","7.0.7-1","7.0.7-1~bpo13+1","7.0.9-1","7.0.9-1~bpo13+1","7.1.1-1~exp1","7.1.10-1","7.1.12-1","7.1.13-1","7.1.2-1~exp1","7.1.3-1","7.1.3-1+sunvdc","7.1.3-1~bpo13+1","7.1.4-1","7.1.5-1","7.1.6-1","7.1.7-1","7.1.7-1~bpo13+1","7.1.8-1","7.1.8-1~bpo13+1","7.1.8-2","7.1.9-1","7.1.9-1+sparc64","7.1~rc2-1~exp1","7.1~rc3-1~exp1","7.1~rc4-1~exp1","7.1~rc4-1~exp2","7.1~rc5-1~exp1","7.1~rc7-1~exp1","7.2.2-1~exp1","7.2.3-1~exp1","7.2~rc3-1~exp1","7.2~rc5-1~exp1","7.2~rc7-1~exp1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-89767.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H"}]}