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authorIan Kent <raven@themaw.net>2007-02-20 16:58:10 -0500
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-02-20 20:10:15 -0500
commitc9ffec48487849bc277de662a6c29aad64653b99 (patch)
tree42f848ada18ac6d241a952e55c765305b4278e90 /fs/autofs4/root.c
parentf50b6f8691cae2e0064c499dd3ef3f31142987f0 (diff)
[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>
Diffstat (limited to 'fs/autofs4/root.c')
-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
655 655
656 /* 656 /*
657 * If this dentry is unhashed, then we shouldn't honour this 657 * If this dentry is unhashed, then we shouldn't honour this
658 * lookup even if the dentry is positive. Returning ENOENT here 658 * lookup. Returning ENOENT here doesn't do the right thing
659 * doesn't do the right thing for all system calls, but it should 659 * for all system calls, but it should be OK for the operations
660 * be OK for the operations we permit from an autofs. 660 * we permit from an autofs.
661 */ 661 */
662 if (dentry->d_inode && d_unhashed(dentry)) { 662 if (dentry->d_inode && d_unhashed(dentry)) {
663 /*
664 * A user space application can (and has done in the past)
665 * remove and re-create this directory during the callback.
666 * This can leave us with an unhashed dentry, but a
667 * successful mount! So we need to perform another
668 * cached lookup in case the dentry now exists.
669 */
670 struct dentry *parent = dentry->d_parent;
671 struct dentry *new = d_lookup(parent, &dentry->d_name);
672 if (new != NULL)
673 dentry = new;
674 else
675 dentry = ERR_PTR(-ENOENT);
676
663 if (unhashed) 677 if (unhashed)
664 dput(unhashed); 678 dput(unhashed);
665 return ERR_PTR(-ENOENT); 679
680 return dentry;
666 } 681 }
667 682
668 if (unhashed) 683 if (unhashed)