[linux-cifs-client] [PATCH] cifs: fix error handling in mount-time DFS referral chasing code

[Jeff Layton]

If the referral is malformed or the hostname can't be resolved, then
the current code generates an oops. Fix it to handle these errors
gracefully.

Reported-by: Sandro Mathys <sm at sandro-mathys.ch>
Signed-off-by: Jeff Layton <jlayton at redhat.com>
---
 fs/cifs/cifs_dfs_ref.c |   12 +++++++++---
 fs/cifs/connect.c      |   13 ++++++++++---
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/fs/cifs/cifs_dfs_ref.c b/fs/cifs/cifs_dfs_ref.c
index 3bb11be..606912d 100644
--- a/fs/cifs/cifs_dfs_ref.c
+++ b/fs/cifs/cifs_dfs_ref.c
@@ -55,7 +55,7 @@ void cifs_dfs_release_automount_timer(void)
  * i.e. strips from UNC trailing path that is not part of share
  * name and fixup missing '\' in the begining of DFS node refferal
  * if neccessary.
- * Returns pointer to share name on success or NULL on error.
+ * Returns pointer to share name on success or ERR_PTR on error.
  * Caller is responsible for freeing returned string.
  */
 static char *cifs_get_share_name(const char *node_name)
@@ -68,7 +68,7 @@ static char *cifs_get_share_name(const char *node_name)
 	UNC = kmalloc(len+2 /*for term null and additional \ if it's missed */,
 			 GFP_KERNEL);
 	if (!UNC)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	/* get share name and server name */
 	if (node_name[1] != '\\') {
@@ -87,7 +87,7 @@ static char *cifs_get_share_name(const char *node_name)
 		cERROR(1, ("%s: no server name end in node name: %s",
 			__func__, node_name));
 		kfree(UNC);
-		return NULL;
+		return ERR_PTR(-EINVAL);
 	}
 
 	/* find sharename end */
@@ -133,6 +133,12 @@ char *cifs_compose_mount_options(const char *sb_mountdata,
 		return ERR_PTR(-EINVAL);
 
 	*devname = cifs_get_share_name(ref->node_name);
+	if (IS_ERR(*devname)) {
+		rc = PTR_ERR(*devname);
+		*devname = NULL;
+		goto compose_mount_options_err;
+	}
+
 	rc = dns_resolve_server_name_to_ip(*devname, &srvIP);
 	if (rc != 0) {
 		cERROR(1, ("%s: Failed to resolve server part of %s to IP: %d",
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index fc44d31..f248688 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -2544,11 +2544,20 @@ remote_path_check:
 
 			if (mount_data != mount_data_global)
 				kfree(mount_data);
+
 			mount_data = cifs_compose_mount_options(
 					cifs_sb->mountdata, full_path + 1,
 					referrals, &fake_devname);
-			kfree(fake_devname);
+
 			free_dfs_info_array(referrals, num_referrals);
+			kfree(fake_devname);
+			kfree(full_path);
+
+			if (IS_ERR(mount_data)) {
+				rc = PTR_ERR(mount_data);
+				mount_data = NULL;
+				goto mount_fail_check;
+			}
 
 			if (tcon)
 				cifs_put_tcon(tcon);
@@ -2556,8 +2565,6 @@ remote_path_check:
 				cifs_put_smb_ses(pSesInfo);
 
 			cleanup_volume_info(&volume_info);
-			FreeXid(xid);
-			kfree(full_path);
 			referral_walks_count++;
 			goto try_mount_again;
 		}
-- 
1.5.5.6