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authorIan Kent <raven@themaw.net>2007-02-20 13:58:10 -0800
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-02-20 17:10:15 -0800
commitc9ffec48487849bc277de662a6c29aad64653b99 (patch)
tree42f848ada18ac6d241a952e55c765305b4278e90
parentf50b6f8691cae2e0064c499dd3ef3f31142987f0 (diff)
downloadlinux-stericsson-c9ffec48487849bc277de662a6c29aad64653b99.tar.gz
[PATCH] autofs4: check for directory re-create in lookup
This problem was identified and fixed some time ago by Jeff Moyer but it fell through the cracks somehow. It is possible that a user space application could remove and re-create a directory during a request. To avoid returning a failure from lookup incorrectly when our current dentry is unhashed we need to check if another positive, hashed dentry matching this one exists and if so return it instead of a fail. Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--fs/autofs4/root.c23
1 files changed, 19 insertions, 4 deletions
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 47adf270106a..b4631046867e 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -655,14 +655,29 @@ static struct dentry *autofs4_lookup(struct inode *dir, struct dentry *dentry, s
/*
* If this dentry is unhashed, then we shouldn't honour this
- * lookup even if the dentry is positive. Returning ENOENT here
- * doesn't do the right thing for all system calls, but it should
- * be OK for the operations we permit from an autofs.
+ * lookup. Returning ENOENT here doesn't do the right thing
+ * for all system calls, but it should be OK for the operations
+ * we permit from an autofs.
*/
if (dentry->d_inode && d_unhashed(dentry)) {
+ /*
+ * A user space application can (and has done in the past)
+ * remove and re-create this directory during the callback.
+ * This can leave us with an unhashed dentry, but a
+ * successful mount! So we need to perform another
+ * cached lookup in case the dentry now exists.
+ */
+ struct dentry *parent = dentry->d_parent;
+ struct dentry *new = d_lookup(parent, &dentry->d_name);
+ if (new != NULL)
+ dentry = new;
+ else
+ dentry = ERR_PTR(-ENOENT);
+
if (unhashed)
dput(unhashed);
- return ERR_PTR(-ENOENT);
+
+ return dentry;
}
if (unhashed)