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>
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@ -32,6 +32,7 @@
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#include <linux/kthread.h>
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#include <linux/pagevec.h>
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#include <linux/freezer.h>
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#include <linux/namei.h>
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#include <asm/uaccess.h>
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#include <asm/processor.h>
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#include <net/ipv6.h>
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@ -2278,6 +2279,7 @@ cifs_mount(struct super_block *sb, struct cifs_sb_info *cifs_sb,
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#ifdef CONFIG_CIFS_DFS_UPCALL
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struct dfs_info3_param *referrals = NULL;
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unsigned int num_referrals = 0;
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int referral_walks_count = 0;
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try_mount_again:
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#endif
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full_path = NULL;
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@ -2525,6 +2527,16 @@ remote_path_check:
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/* get referral if needed */
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if (rc == -EREMOTE) {
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#ifdef CONFIG_CIFS_DFS_UPCALL
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if (referral_walks_count > MAX_NESTED_LINKS) {
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/*
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* BB: when we implement proper loop detection,
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* we will remove this check. But now we need it
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* to prevent an indefinite loop if 'DFS tree' is
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* misconfigured (i.e. has loops).
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*/
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rc = -ELOOP;
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goto mount_fail_check;
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}
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/* convert forward to back slashes in prepath here if needed */
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if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_POSIX_PATHS) == 0)
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convert_delimiter(cifs_sb->prepath,
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@ -2558,6 +2570,7 @@ remote_path_check:
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cleanup_volume_info(&volume_info);
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FreeXid(xid);
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kfree(full_path);
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referral_walks_count++;
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goto try_mount_again;
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}
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#else /* No DFS support, return error on mount */
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