Added loop check when mounting DFS tree.
Added loop check when mounting DFS tree. mount will fail with
ELOOP if referral walks exceed MAX_NESTED_LINK count.
Signed-off-by: Igor Mammedov <niallain@gmail.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
index 579a628..7e5d4fd 100644
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -32,6 +32,7 @@
#include <linux/kthread.h>
#include <linux/pagevec.h>
#include <linux/freezer.h>
+#include <linux/namei.h>
#include <asm/uaccess.h>
#include <asm/processor.h>
#include <net/ipv6.h>
@@ -2278,6 +2279,7 @@
#ifdef CONFIG_CIFS_DFS_UPCALL
struct dfs_info3_param *referrals = NULL;
unsigned int num_referrals = 0;
+ int referral_walks_count = 0;
try_mount_again:
#endif
full_path = NULL;
@@ -2525,6 +2527,16 @@
/* get referral if needed */
if (rc == -EREMOTE) {
#ifdef CONFIG_CIFS_DFS_UPCALL
+ if (referral_walks_count > MAX_NESTED_LINKS) {
+ /*
+ * BB: when we implement proper loop detection,
+ * we will remove this check. But now we need it
+ * to prevent an indefinite loop if 'DFS tree' is
+ * misconfigured (i.e. has loops).
+ */
+ rc = -ELOOP;
+ goto mount_fail_check;
+ }
/* convert forward to back slashes in prepath here if needed */
if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) == 0)
convert_delimiter(cifs_sb->prepath,
@@ -2558,6 +2570,7 @@
cleanup_volume_info(&volume_info);
FreeXid(xid);
kfree(full_path);
+ referral_walks_count++;
goto try_mount_again;
}
#else /* No DFS support, return error on mount */