lkml.org 
[lkml]   [2007]   [Feb]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 2/2] autofs4 - check for directory re-create in lookup

Hi Andrew,

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>

Ian

---

--- linux-2.6.20/fs/autofs4/root.c.lookup-check-unhased 2007-02-12 13:49:46.000000000 +0900
+++ linux-2.6.20/fs/autofs4/root.c 2007-02-12 13:54:58.000000000 +0900
@@ -655,14 +655,29 @@ static struct dentry *autofs4_lookup(str

/*
* 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)
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
\
 
 \ /
  Last update: 2007-02-15 05:25    [W:0.042 / U:0.212 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site