[PATCH] cifs: parse_dfs_referrals: prevent oob on malformed input

[PATCH] cifs: parse_dfs_referrals: prevent oob on malformed input

[Eugene Korenevsky]

Malicious SMB server can send invalid reply to FSCTL_DFS_GET_REFERRALS

- reply smaller than sizeof(struct get_dfs_referral_rsp)
- reply with number of referrals smaller than NumberOfReferrals in the
header

Processing of such replies will cause oob.

Return -EINVAL error on such replies to prevent oob-s.

Signed-off-by: Eugene Korenevsky <ekorenevsky@aliyun.com>
---
 fs/smb/client/misc.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/fs/smb/client/misc.c b/fs/smb/client/misc.c
index dda6dece802a..987f0ca73123 100644
--- a/fs/smb/client/misc.c
+++ b/fs/smb/client/misc.c
@@ -916,6 +916,14 @@ parse_dfs_referrals(struct get_dfs_referral_rsp *rsp, u32 rsp_size,
 	char *data_end;
 	struct dfs_referral_level_3 *ref;
 
+	if (rsp_size < sizeof(*rsp)) {
+		cifs_dbg(VFS | ONCE,
+			 "%s: header is malformed (size is %u, must be %lu)\n",
+			 __func__, rsp_size, sizeof(*rsp));
+		rc = -EINVAL;
+		goto parse_DFS_referrals_exit;
+	}
+
 	*num_of_nodes = le16_to_cpu(rsp->NumberOfReferrals);
 
 	if (*num_of_nodes < 1) {
@@ -925,6 +933,15 @@ parse_dfs_referrals(struct get_dfs_referral_rsp *rsp, u32 rsp_size,
 		goto parse_DFS_referrals_exit;
 	}
 
+	if (sizeof(*rsp) + *num_of_nodes * sizeof(REFERRAL3) > rsp_size) {
+		cifs_dbg(VFS | ONCE,
+			 "%s: malformed buffer (size is %u, must be at least %lu)\n",
+			 __func__, rsp_size,
+			 sizeof(*rsp) + *num_of_nodes * sizeof(REFERRAL3));
+		rc = -EINVAL;
+		goto parse_DFS_referrals_exit;
+	}
+
 	ref = (struct dfs_referral_level_3 *) &(rsp->referrals);
 	if (ref->VersionNumber != cpu_to_le16(3)) {
 		cifs_dbg(VFS, "Referrals of V%d version are not supported, should be V3\n",
-- 
2.47.3