releases/3.6.8/cifs-do-not-lookup-hashed-negative-dentry-in-cifs_atomic_open.patch

   1 From 3798f47aa276b332c30da499cb4df4577e2f8872 Mon Sep 17 00:00:00 2001
   2 From: Sachin Prabhu <sprabhu@redhat.com>
   3 Date: Mon, 5 Nov 2012 11:39:32 +0000
   4 Subject: cifs: Do not lookup hashed negative dentry in cifs_atomic_open
   5
   6 From: Sachin Prabhu <sprabhu@redhat.com>
   7
   8 commit 3798f47aa276b332c30da499cb4df4577e2f8872 upstream.
   9
  10 We do not need to lookup a hashed negative directory since we have
  11 already revalidated it before and have found it to be fine.
  12
  13 This also prevents a crash in cifs_lookup() when it attempts to rehash
  14 the already hashed negative lookup dentry.
  15
  16 The patch has been tested using the reproducer at
  17 https://bugzilla.redhat.com/show_bug.cgi?id=867344#c28
  18
  19 Reported-by: Vit Zahradka <vit.zahradka@tiscali.cz>
  20 Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
  21 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  22
  23 ---
  24  fs/cifs/dir.c |   11 ++++++++++-
  25  1 file changed, 10 insertions(+), 1 deletion(-)
  26
  27 --- a/fs/cifs/dir.c
  28 +++ b/fs/cifs/dir.c
  29 @@ -392,7 +392,16 @@ cifs_atomic_open(struct inode *inode, st
  30          * in network traffic in the other paths.
  31          */
  32         if (!(oflags & O_CREAT)) {
  33 -               struct dentry *res = cifs_lookup(inode, direntry, 0);
  34 +               struct dentry *res;
  35 +
  36 +               /*
  37 +                * Check for hashed negative dentry. We have already revalidated
  38 +                * the dentry and it is fine. No need to perform another lookup.
  39 +                */
  40 +               if (!d_unhashed(direntry))
  41 +                       return -ENOENT;
  42 +
  43 +               res = cifs_lookup(inode, direntry, 0);
  44                 if (IS_ERR(res))
  45                         return PTR_ERR(res);
  46