Re: [PATCH] btrfs: backref: this patch fixes a null pointer dereference bug.

On 2020/8/7 上午11:34, Boleyn Su wrote:

Thanks for the review. BTW, do I need to do anything else or just leave
it to you?

If you mean adding the extra reviewed-by tags, no. It's handled by the
awesome maintainer David.

But if you mean to find more btrfs bugs, then keep going your awesome work!

Thanks,
Qu

On Thu, Aug 6, 2020 at 4:04 PM Qu Wenruo <quwenruo.btrfs@gmx.com
<mailto:quwenruo.btrfs@gmx.com>> wrote:



    On 2020/8/6 下午2:31, Boleyn Su wrote:
    > The `if (!ret)` check will always be false and it may result in
    ret->path
    > being dereferenced while it is a null pointer.
    >
    > Fixes: a37f232b7b65 ("btrfs: backref: introduce the skeleton of
    btrfs_backref_iter")
    > Cc: Chris Mason <clm@fb.com <mailto:clm@fb.com>>
    > Cc: Josef Bacik <josef@toxicpanda.com <mailto:josef@toxicpanda.com>>
    > Cc: David Sterba <dsterba@suse.com <mailto:dsterba@suse.com>>
    > Cc: Boleyn Su <boleyn.su@gmail.com <mailto:boleyn.su@gmail.com>>
    > Cc: linux-btrfs@vger.kernel.org <mailto:linux-btrfs@vger.kernel.org>
    > Signed-off-by: Boleyn Su <boleynsu@google.com
    <mailto:boleynsu@google.com>>

    Nice catch.

    Reviewed-by: Qu Wenruo <wqu@suse.com <mailto:wqu@suse.com>>

    Thanks,
    Qu
    > ---
    >  fs/btrfs/backref.c | 2 +-
    >  1 file changed, 1 insertion(+), 1 deletion(-)
    >
    > diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c
    > index ea10f7bc9..ea1c28ccb 100644
    > --- a/fs/btrfs/backref.c
    > +++ b/fs/btrfs/backref.c
    > @@ -2303,7 +2303,7 @@ struct btrfs_backref_iter
    *btrfs_backref_iter_alloc(
    >               return NULL;
    > 
    >       ret->path = btrfs_alloc_path();
    > -     if (!ret) {
    > +     if (!ret->path) {
    >               kfree(ret);
    >               return NULL;
    >       }
    >



-- 
Boleyn Su (simplified Chinese: 苏蕉; traditional Chinese: 蘇蕉; Pinyin:
Sū Jiāo; Katakana: スージャオ)

My PGP public key is available at boleyn.su/pgp <https://boleyn.su/pgp>.