ksmbd: fix out-of-bounds in parse_sec_desc()

commit d6e13e1 upstream.

If osidoffset, gsidoffset and dacloffset could be greater than smb_ntsd
struct size. If it is smaller, It could cause slab-out-of-bounds.
And when validating sid, It need to check it included subauth array size.

Cc: stable@vger.kernel.org
Reported-by: Norbert Szetei <norbert@doyensec.com>
Tested-by: Norbert Szetei <norbert@doyensec.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: namjaejeon

fs/smb/server/smbacl.c

@@ -807,6 +807,13 @@ static int parse_sid(struct smb_sid *psid, char *end_of_acl)
 		return -EINVAL;
 	}
 
+	if (!psid->num_subauth)
+		return 0;
+
+	if (psid->num_subauth > SID_MAX_SUB_AUTHORITIES ||
+	    end_of_acl < (char *)psid + 8 + sizeof(__le32) * psid->num_subauth)
+		return -EINVAL;
+
 	return 0;
 }
 
@@ -848,6 +855,9 @@ int parse_sec_desc(struct mnt_idmap *idmap, struct smb_ntsd *pntsd,
 	pntsd->type = cpu_to_le16(DACL_PRESENT);
 
 	if (pntsd->osidoffset) {
+		if (le32_to_cpu(pntsd->osidoffset) < sizeof(struct smb_ntsd))
+			return -EINVAL;
+
 		rc = parse_sid(owner_sid_ptr, end_of_acl);
 		if (rc) {
 			pr_err("%s: Error %d parsing Owner SID\n", __func__, rc);
@@ -863,6 +873,9 @@ int parse_sec_desc(struct mnt_idmap *idmap, struct smb_ntsd *pntsd,
 	}
 
 	if (pntsd->gsidoffset) {
+		if (le32_to_cpu(pntsd->gsidoffset) < sizeof(struct smb_ntsd))
+			return -EINVAL;
+
 		rc = parse_sid(group_sid_ptr, end_of_acl);
 		if (rc) {
 			pr_err("%s: Error %d mapping Owner SID to gid\n",
@@ -884,6 +897,9 @@ int parse_sec_desc(struct mnt_idmap *idmap, struct smb_ntsd *pntsd,
 		pntsd->type |= cpu_to_le16(DACL_PROTECTED);
 
 	if (dacloffset) {
+		if (dacloffset < sizeof(struct smb_ntsd))
+			return -EINVAL;
+
 		parse_dacl(idmap, dacl_ptr, end_of_acl,
 			   owner_sid_ptr, group_sid_ptr, fattr);
 	}