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| author | Ian Kent <raven@themaw.net> | 2007-02-20 13:58:10 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-02-20 17:10:15 -0800 |
| commit | c9ffec48487849bc277de662a6c29aad64653b99 (patch) | |
| tree | 42f848ada18ac6d241a952e55c765305b4278e90 /fs | |
| parent | f50b6f8691cae2e0064c499dd3ef3f31142987f0 (diff) | |
| download | kernel-crypto-c9ffec48487849bc277de662a6c29aad64653b99.tar.gz kernel-crypto-c9ffec48487849bc277de662a6c29aad64653b99.tar.xz kernel-crypto-c9ffec48487849bc277de662a6c29aad64653b99.zip | |
[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')
| -rw-r--r-- | fs/autofs4/root.c | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c index 47adf270106..b4631046867 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) |