linux-kernel - [33/45] fix LOOKUP_FOLLOW on automount "symlinks"

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Message-Id: <20100330225001.595812327@linux.site>
Date:	Tue, 30 Mar 2010 15:48:53 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Al Viro <viro@...iv.linux.org.uk>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [33/45] fix LOOKUP_FOLLOW on automount "symlinks"

2.6.27-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Al Viro <viro@...IV.linux.org.uk>

commit ac278a9c505092dd82077a2446af8f9fc0d9c095 upstream.

Make sure that automount "symlinks" are followed regardless of LOOKUP_FOLLOW;
it should have no effect on them.

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 fs/namei.c |   14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

--- a/fs/namei.c
+++ b/fs/namei.c
@@ -841,6 +841,17 @@ fail:
 }
 
 /*
+ * This is a temporary kludge to deal with "automount" symlinks; proper
+ * solution is to trigger them on follow_mount(), so that do_lookup()
+ * would DTRT.  To be killed before 2.6.34-final.
+ */
+static inline int follow_on_final(struct inode *inode, unsigned lookup_flags)
+{
+	return inode && unlikely(inode->i_op->follow_link) &&
+		((lookup_flags & LOOKUP_FOLLOW) || S_ISDIR(inode->i_mode));
+}
+
+/*
  * Name resolution.
  * This is the basic name resolution function, turning a pathname into
  * the final dentry. We expect 'base' to be positive and a directory.
@@ -984,8 +995,7 @@ last_component:
 		if (err)
 			break;
 		inode = next.dentry->d_inode;
-		if ((lookup_flags & LOOKUP_FOLLOW)
-		    && inode && inode->i_op && inode->i_op->follow_link) {
+		if (follow_on_final(inode, lookup_flags)) {
 			err = do_follow_link(&next, nd);
 			if (err)
 				goto return_err;


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