Gitweb:     
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=c9ffec48487849bc277de662a6c29aad64653b99
Commit:     c9ffec48487849bc277de662a6c29aad64653b99
Parent:     f50b6f8691cae2e0064c499dd3ef3f31142987f0
Author:     Ian Kent <[EMAIL PROTECTED]>
AuthorDate: Tue Feb 20 13:58:10 2007 -0800
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Tue Feb 20 17:10:15 2007 -0800

    [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 <[EMAIL PROTECTED]>
    Signed-off-by: Ian Kent <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
 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 47adf27..b463104 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)
-
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