Revert the following change:
commit 0ec26fd0698285b31248e34bf1abb022c00f23d6
Author: Miklos Szeredi <mszeredi@xxxxxxx>
Date: Mon Sep 5 18:06:26 2011 +0200
Subject: vfs: automount should ignore LOOKUP_FOLLOW
which makes stat(), getxattr(), etc. behave as lstat(), lgetxattr(), etc. with
respect to automounting: it prevents them from triggering terminal automounts.
The problem with this is that this breaks nfs_follow_remote_path() used by NFS4
to find the root object to mount for the mount() syscall.
This can be tested by the following procedure:
(1) Export a directory from an NFS4 server that has something mounted upon it
and that isn't "/" - say, for example, "/scratch". It must have a
different FSID from "/".
(2) Mount this on the client.
mount sirius:/scratch /mnt
(3) List the contents of the client's mountpoint:
ls /mnt
(4) Examine /proc/fs/nfsfs/volumes. You should see one entry (assuming
nothing else is NFS mounted) :
NV SERVER PORT DEV FSID FSC
v4 200108b001940000021125fffe84efad 801 0:34 1:0 no
which corresponds to the filesystem mounted on /scratch on the server.
If, however, you see two entries:
NV SERVER PORT DEV FSID FSC
v4 200108b001940000021125fffe84efad 801 0:33 0:0 no
v4 200108b001940000021125fffe84efad 801 0:34 1:0 no
then it went wrong.
When it goes wrong, what happens is that nfs_follow_remote_path() walks from
the rootfh to the remote directory (/scratch) using vfs_path_lookup(). It
passes LOOKUP_FOLLOW to vfs_path_lookup() to tell it to transit terminal
symlinks and terminal automounts. Unfortunately, with the problematic commit,
LOOKUP_FOLLOW now expressly does not follow terminal automounts, and so the
dummy automount directory fabricated in fsid 0:0 gets mounted instead of the
root of fsid 1:0.
Reported-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---
fs/namei.c | 33 ++++++++++++++++++---------------
1 files changed, 18 insertions(+), 15 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index f478836..c64b81d 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -727,22 +727,25 @@ static int follow_automount(struct path *path, unsigned flags,
if ((flags & LOOKUP_NO_AUTOMOUNT) && !(flags & LOOKUP_PARENT))
return -EISDIR; /* we actually want to stop here */
- /* We don't want to mount if someone's just doing a stat -
- * unless they're stat'ing a directory and appended a '/' to
- * the name.
- *
- * We do, however, want to mount if someone wants to open or
- * create a file of any type under the mountpoint, wants to
- * traverse through the mountpoint or wants to open the
- * mounted directory. Also, autofs may mark negative dentries
- * as being automount points. These will need the attentions
- * of the daemon to instantiate them before they can be used.
+ /*
+ * We don't want to mount if someone's just doing a stat and they've
+ * set AT_SYMLINK_NOFOLLOW - unless they're stat'ing a directory and
+ * appended a '/' to the name.
*/
- if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
- LOOKUP_OPEN | LOOKUP_CREATE)) &&
- path->dentry->d_inode)
- return -EISDIR;
-
+ if (!(flags & LOOKUP_FOLLOW)) {
+ /* We do, however, want to mount if someone wants to open or
+ * create a file of any type under the mountpoint, wants to
+ * traverse through the mountpoint or wants to open the mounted
+ * directory.
+ * Also, autofs may mark negative dentries as being automount
+ * points. These will need the attentions of the daemon to
+ * instantiate them before they can be used.
+ */
+ if (!(flags & (LOOKUP_PARENT | LOOKUP_DIRECTORY |
+ LOOKUP_OPEN | LOOKUP_CREATE)) &&
+ path->dentry->d_inode)
+ return -EISDIR;
+ }
current->total_link_count++;
if (current->total_link_count >= 40)
return -ELOOP;
--
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