[ 085/108] vfs: fix d_ancestor() case in d_materialize_unique

From: Greg KH
Date: Fri Mar 30 2012 - 17:07:36 EST

3.0-stable review patch. If anyone has any objections, please let me know.


From: Michel Lespinasse <walken@xxxxxxxxxx>

commit b18dafc86bb879d2f38a1743985d7ceb283c2f4d upstream.

In d_materialise_unique() there are 3 subcases to the 'aliased dentry'
case; in two subcases the inode i_lock is properly released but this
does not occur in the -ELOOP subcase.

This seems to have been introduced by commit 1836750115f2 ("fix loop
checks in d_materialise_unique()").

Signed-off-by: Michel Lespinasse <walken@xxxxxxxxxx>
[ Added a comment, and moved the unlock to where we generate the -ELOOP,
which seems to be more natural.

You probably can't actually trigger this without a buggy network file
server - d_materialize_unique() is for finding aliases on non-local
filesystems, and the d_ancestor() case is for a hardlinked directory

But we should be robust in the case of such buggy servers anyway. ]
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

fs/dcache.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -2433,6 +2433,7 @@ struct dentry *d_materialise_unique(stru
if (d_ancestor(alias, dentry)) {
/* Check for loops */
actual = ERR_PTR(-ELOOP);
+ spin_unlock(&inode->i_lock);
} else if (IS_ROOT(alias)) {
/* Is this an anonymous mountpoint that we
* could splice into our tree? */
@@ -2442,7 +2443,7 @@ struct dentry *d_materialise_unique(stru
goto found;
} else {
/* Nope, but we must(!) avoid directory
- * aliasing */
+ * aliasing. This drops inode->i_lock */
actual = __d_unalias(inode, dentry, alias);

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