cifs: For SMB2 security informaion query, check for minimum sized security descriptor instead of sizeof FileAllInformation class

Validate_buf () function checks for an expected minimum sized response
passed to query_info() function.
For security information, the size of a security descriptor can be
smaller (one subauthority, no ACEs) than the size of the structure
that defines FileInfoClass of FileAllInformation.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=199725
Cc: <stable@vger.kernel.org>
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Reviewed-by: Noah Morrison <noah.morrison@rubrik.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/fs/cifs/cifsacl.h b/fs/cifs/cifsacl.h
index 4f3884835267..dd95a6fa24bf 100644
--- a/fs/cifs/cifsacl.h
+++ b/fs/cifs/cifsacl.h
@@ -98,4 +98,18 @@ struct cifs_ace {
 	struct cifs_sid sid; /* ie UUID of user or group who gets these perms */
 } __attribute__((packed));
 
+/*
+ * Minimum security identifier can be one for system defined Users
+ * and Groups such as NULL SID and World or Built-in accounts such
+ * as Administrator and Guest and consists of
+ * Revision + Num (Sub)Auths + Authority + Domain (one Subauthority)
+ */
+#define MIN_SID_LEN  (1 + 1 + 6 + 4) /* in bytes */
+
+/*
+ * Minimum security descriptor can be one without any SACL and DACL and can
+ * consist of revision, type, and two sids of minimum size for owner and group
+ */
+#define MIN_SEC_DESC_LEN  (sizeof(struct cifs_ntsd) + (2 * MIN_SID_LEN))
+
 #endif /* _CIFSACL_H */