CVE-2026-90153ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size

Official description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: bound smb_check_perm_dacl() ACE walks by DACL size smb_check_perm_dacl() validates that the DACL fits inside the NT security descriptor, but then bounds its two ACE walks by the remaining NTSD length (acl_size) rather than the DACL's declared size (pdacl_size). When pdacl->size is smaller than the trailing NTSD buffer, bytes after the declared DACL boundary - still inside the stored security descriptor - are parsed as ACEs during access checks. A crafted DACL can place an access-granting ACE beyond pdacl->size, and the current code accepts it during SMB2_CREATE access validation, while parse_dacl() and smb_inherit_dacl() stop at pdacl_size. Bound both ACE walks by pdacl_size to match the DACL boundary semantics used elsewhere in the server. Validation: - semantic KUnit harness shows the post-boundary ACE is selected before the fix and rejected (EACCES) after it - linux master (7.2-rc6), x86_64

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/930dcdd888eabf166589e020dcbf6d15b5e13305
• https://git.kernel.org/stable/c/a2051ffe452afad52f580b85a3fd8851933b1e7c
• https://git.kernel.org/stable/c/a29f57a14c939586d84d7fd6a029bd1fd170098f
• https://git.kernel.org/stable/c/a4a307d149327dad5fb25187e1b03cebd1b04de6
• https://git.kernel.org/stable/c/8e4f75e979c1d9a51b0a48ac33d0cfd5f039ec67
• https://git.kernel.org/stable/c/79decd88dd3f0d42e7fb0689b1a7853bfa302459