Re: [PATCH] cifs: cope with negative dentries in cifs_get_root

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2011/8/5 Jeff Layton <jlayton@xxxxxxxxxx>:
> The loop around lookup_one_len doesn't handle the case where it might
> return a negative dentry, which can cause an oops on the next pass
> through the loop. Check for that and break out of the loop with an
> error of -ENOENT if there is one.
>
> Fixes the panic reported here:
>
>    https://bugzilla.redhat.com/show_bug.cgi?id=727927
>
> Reported-by: TR Bentley <home@xxxxxxxxxxxxxxx>
> Reported-by: Iain Arnell <iarnell@xxxxxxxxx>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxx
> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
> ---
>  fs/cifs/cifsfs.c |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
> index 212e562..f93eb94 100644
> --- a/fs/cifs/cifsfs.c
> +++ b/fs/cifs/cifsfs.c
> @@ -563,6 +563,10 @@ cifs_get_root(struct smb_vol *vol, struct super_block *sb)
>                mutex_unlock(&dir->i_mutex);
>                dput(dentry);
>                dentry = child;
> +               if (!dentry->d_inode) {

dentry can be NULL here (returned from lookup_one_len) and it can
cause a null pointer dereference.

> +                       dput(dentry);
> +                       dentry = ERR_PTR(-ENOENT);
> +               }
>        } while (!IS_ERR(dentry));
>        _FreeXid(xid);
>        kfree(full_path);
> --
> 1.7.6
>
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-- 
Best regards,
Pavel Shilovsky.
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