2012/10/30 Sachin Prabhu <[email protected]>:
> 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
>
> Cc: <[email protected]> # 3.6.x
> Reported-by: Vit Zahradka <[email protected]>
> Signed-off-by: Sachin Prabhu <[email protected]>
> ---
>  fs/cifs/dir.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/fs/cifs/dir.c b/fs/cifs/dir.c
> index 7c0a812..e26d0a6 100644
> --- a/fs/cifs/dir.c
> +++ b/fs/cifs/dir.c
> @@ -398,6 +398,12 @@ cifs_atomic_open(struct inode *inode, struct dentry 
> *direntry,
>          * in network traffic in the other paths.
>          */
>         if (!(oflags & O_CREAT)) {
> +               /* Check for hashed negative dentry. We have already 
> revalidated
> +                * the dentry and it is fine. No need to perform another 
> lookup.
> +                */

Patch looks ok, but the comment above doesn't match the kernel
CodingStyle for block comments. While cifs code has a many places
where it doesn't follow the style, we should keep new code as clean as
possible.

> +               if (!d_unhashed(direntry))
> +                       return -ENOENT;
> +
>                 struct dentry *res = cifs_lookup(inode, direntry, 0);
>                 if (IS_ERR(res))
>                         return PTR_ERR(res);
> --
> 1.7.11.7
>
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-- 
Best regards,
Pavel Shilovsky.
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