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    Subject[ 14/83] cifs: Do not lookup hashed negative dentry in cifs_atomic_open
    Date
    3.6-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Sachin Prabhu <sprabhu@redhat.com>

    commit 3798f47aa276b332c30da499cb4df4577e2f8872 upstream.

    We do not need to lookup a hashed negative directory since we have
    already revalidated it before and have found it to be fine.

    This also prevents a crash in cifs_lookup() when it attempts to rehash
    the already hashed negative lookup dentry.

    The patch has been tested using the reproducer at
    https://bugzilla.redhat.com/show_bug.cgi?id=867344#c28

    Reported-by: Vit Zahradka <vit.zahradka@tiscali.cz>
    Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    fs/cifs/dir.c | 11 ++++++++++-
    1 file changed, 10 insertions(+), 1 deletion(-)

    --- a/fs/cifs/dir.c
    +++ b/fs/cifs/dir.c
    @@ -392,7 +392,16 @@ cifs_atomic_open(struct inode *inode, st
    * in network traffic in the other paths.
    */
    if (!(oflags & O_CREAT)) {
    - struct dentry *res = cifs_lookup(inode, direntry, 0);
    + struct dentry *res;
    +
    + /*
    + * Check for hashed negative dentry. We have already revalidated
    + * the dentry and it is fine. No need to perform another lookup.
    + */
    + if (!d_unhashed(direntry))
    + return -ENOENT;
    +
    + res = cifs_lookup(inode, direntry, 0);
    if (IS_ERR(res))
    return PTR_ERR(res);




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