ksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops

Summary

In the Linux kernel, the following vulnerability has been resolved: ksmbd: OOB read regression in smb_check_perm_dacl() ACE-walk loops Commit d07b26f39246 ("ksmbd: require minimum ACE size in smb_check_perm_dacl()") introduced a transposed bounds check: if (offsetof(struct smb_ace, sid) + aces_size < CIFS_SID_BASE_SIZE) Since offsetof(..sid) is 8 and CIFS_SID_BASE_SIZE is 8, this evaluates to `aces_size < 0`. Because `aces_size` is always non-negative, this check becomes dead code and never breaks the loop. Worse, that commit removed the old 4-byte guard, meaning the loop now reads `ace->size` (offset 2) even when `aces_size` is 0-3 bytes. This re-opens a 2-byte heap out-of-bounds (OOB) read past the pntsd allocation during subsequent SMB2_CREATE operations. Fix this by properly transposing the comparison to require at least 16 bytes (8-byte offset + 8-byte SID base), matching the correct form used in smb_inherit_dacl().

Timeline

1. Jul 19, 2026, 2:55 PM UTCCVE published
2. Aug 5, 2026, 12:37 PM UTCRecord last updated

Affected versions

• Linux Linux

  Version range not reported

• Linux Linux

  From 6.6.140 · fixed in 6.6.143; From 6.12.84 · fixed in 6.12.93; From 6.18.25 · fixed in 6.18.35; From 7.0.2 · fixed in 7.0.12

References 7