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Commit 5c2503a8 authored by Igor Mammedov's avatar Igor Mammedov Committed by Steve French
Browse files

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: default avatarIgor Mammedov <niallain@gmail.com>
Acked-by: default avatarJeff Layton <jlayton@redhat.com>
Signed-off-by: default avatarSteve French <sfrench@us.ibm.com>
parent 1af28ceb

fs/cifs/connect.c

+13 −0
Original line number Diff line number Diff line
@@ -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 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb, 
#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 @@ remote_path_check: 
	/* 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 @@ remote_path_check: 
			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 */