smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid

Summary

In the Linux kernel, the following vulnerability has been resolved: smb: client: honor forceuid/forcegid when mapping SIDs to uid/gid When the administrator mounts with forceuid or forcegid (uid=/gid= mount options), they expect all files to appear owned by the specified user/group. However, several code paths unconditionally called sid_to_id() to overwrite cf_uid/cf_gid with server-provided values, ignoring the administrator's explicit override: • smb311_posix_info_to_fattr() (stat via POSIX extensions) • cifs_posix_to_fattr() (readdir via POSIX extensions) • parse_sec_desc() (CIFS ACL ownership mapping) This allowed an untrusted server to dictate local file ownership even when the mount was configured to force specific uid/gid values. Fix all three call sites to check CIFS_MOUNT_OVERR_UID and CIFS_MOUNT_OVERR_GID before calling sid_to_id(), following the same pattern already used by cifs_unix_basic_to_fattr() for unix extensions.

Timeline

1. Sep 25, 2026, 10:21 AM UTCCVE published
2. Oct 21, 2026, 12:53 PM UTCRecord last updated

Affected versions

• Linux Linux

  From 9409ae58e0759d010b347e7b19ebc90ab5d4b98f · fixed in be6eccccec867c22d7c65fab4ea4e91ec3d5b8c6; From 9409ae58e0759d010b347e7b19ebc90ab5d4b98f · fixed in bc35de451c128d399ad185d6269f8847e97cd1c9; From 9409ae58e0759d010b347e7b19ebc90ab5d4b98f · fixed in 6ac7a29691558bed18e2df1780636b8aa0fd13d5; From 9409ae58e0759d010b347e7b19ebc90ab5d4b98f · fixed in e1b74f8f8c1d13190b09fe623b729d36b7ac22a8; From 9409ae58e0759d010b347e7b19ebc90ab5d4b98f · fixed in 18a72975e9f35aadecc75b031f693f2d1f49308f

• Linux Linux

  3.0

• KernelLinux

  From 3.0.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.114; From 6.13.0 · fixed in 6.18.57; From 6.19.0 · fixed in 7.2.7

References 5