CVE-2026-97554smb: client: avoid using uninitialized SIDs in cifs_posix_to_fattr()

Official description

In the Linux kernel, the following vulnerability has been resolved: smb: client: avoid using uninitialized SIDs in cifs_posix_to_fattr() cifs_posix_to_fattr() ignores the return value of posix_info_parse(). When a malformed POSIX directory entry is encountered (e.g. invalid SID lengths from an untrusted server), posix_info_parse() returns -1 without populating the 'parsed' struct. The uninitialized stack memory in parsed.owner and parsed.group is then passed to sid_to_id(), which processes the garbage bytes and passes them to request_key() to construct a SID string, potentially leaking kernel stack contents to the userspace idmap daemon. Fix this by checking the return value and skipping the SID-to-id mapping when parsing fails. The remaining fattr fields (timestamps, mode, etc.) are populated directly from the 'info' pointer so they are unaffected.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/1915b69e36906968e2b698699d0f219875ae846e
• https://git.kernel.org/stable/c/604feb3e8141bf11f5afd48d36d401fee5af9536
• https://git.kernel.org/stable/c/33106019c3be57b5fc6411cfaad6d98214a51265
• https://git.kernel.org/stable/c/2be31f252ade791b84f7164991f14436aed1d4b9
• https://git.kernel.org/stable/c/c9a8b60ce140a68d172452f418137fc7ddbae7db
• https://git.kernel.org/stable/c/da6e25842431982d5a53cf00d925b98c690f4467