linux-kernel - Re: [PATCH] cifs: check kzalloc return

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Message-ID: <CAH2r5mtrgq-tiSvLrc3sD_Op1HD0OFz2xOMywPoN=iu2nVShrQ@mail.gmail.com>
Date:   Thu, 20 Dec 2018 23:53:04 -0600
From:   Steve French <smfrench@...il.com>
To:     Joe Perches <joe@...ches.com>
Cc:     Nicholas Mc Guire <der.herr@...r.at>,
        Steve French <sfrench@...ba.org>,
        CIFS <linux-cifs@...r.kernel.org>,
        samba-technical <samba-technical@...ts.samba.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Nicholas Mc Guire <hofrat@...dl.org>
Subject: Re: [PATCH] cifs: check kzalloc return

Updated the patch with Joe's signed off and Nicholas's reviewed-by and
pushed to cifs-2.6.git for-next

See attached.

On Wed, Dec 19, 2018 at 4:58 AM Joe Perches via samba-technical
<samba-technical@...ts.samba.org> wrote:
>
> On Wed, 2018-12-19 at 08:22 +0100, Nicholas Mc Guire wrote:
> > On Tue, Dec 18, 2018 at 09:33:58AM -0800, Joe Perches wrote:
> > > On Tue, 2018-12-18 at 17:27 +0100, Nicholas Mc Guire wrote:
> > > > kzalloc can return NULL so a check is needed. While there is a
> > > > check for ret_buf there is no check for the allocation of
> > > > ret_buf->crfid.fid - this check is thus added. Both call-sites
> > > > of tconInfoAlloc() check for NULL return of tconInfoAlloc()
> > > > so returning NULL on failure of kzalloc() here seems appropriate.
> > > > As the kzalloc() is the only thing here that can fail it is
> > > > moved to the beginning so as not to initialize other resources
> > > > on failure of kzalloc.
> > > >
> > > Perhaps use a more common style by returning early on the
> > > first possible failure too so the block can be unindented.
> []
> > > yup the restructured cleanup would be the better way to go
> >
> > rather than making this two patches I guess it would be the
> > best to just skip the intermediate kzalloc only cleanup -
> > atleast I see little value in that intermediat step - so
> > could you take care of the kzalloc() in your refactoring
> > please ?
>
> I did that in the patch I proposed, which is trivial.
> If you want to take it, please do.
>
> If you want a sign-off:
>
> Signed-off-by: Joe Perches <joe@...ches.com>
>
> > > diff --git a/fs/cifs/misc.c b/fs/cifs/misc.c
> []
> > > @@ -111,21 +111,27 @@ struct cifs_tcon *
> > >  tconInfoAlloc(void)
> > >  {
> > >     struct cifs_tcon *ret_buf;
> > > -   ret_buf = kzalloc(sizeof(struct cifs_tcon), GFP_KERNEL);
> > > -   if (ret_buf) {
> > > -           atomic_inc(&tconInfoAllocCount);
> > > -           ret_buf->tidStatus = CifsNew;
> > > -           ++ret_buf->tc_count;
> > > -           INIT_LIST_HEAD(&ret_buf->openFileList);
> > > -           INIT_LIST_HEAD(&ret_buf->tcon_list);
> > > -           spin_lock_init(&ret_buf->open_file_lock);
> > > -           mutex_init(&ret_buf->crfid.fid_mutex);
> > > -           ret_buf->crfid.fid = kzalloc(sizeof(struct cifs_fid),
> > > -                                        GFP_KERNEL);
> > > -           spin_lock_init(&ret_buf->stat_lock);
> > > -           atomic_set(&ret_buf->num_local_opens, 0);
> > > -           atomic_set(&ret_buf->num_remote_opens, 0);
> > > +
> > > +   ret_buf = kzalloc(sizeof(*ret_buf), GFP_KERNEL);
> > > +   if (!ret_buf)
> > > +           return NULL;
> > > +   ret_buf->crfid.fid = kzalloc(sizeof(*ret_buf->crfid.fid), GFP_KERNEL);
> > > +   if (!ret_buf->crfid.fid) {
> > > +           kfree(ret_buf);
> > > +           return NULL;
> > >     }
> > > +
> > > +   atomic_inc(&tconInfoAllocCount);
> > > +   ret_buf->tidStatus = CifsNew;
> > > +   ++ret_buf->tc_count;
> > > +   INIT_LIST_HEAD(&ret_buf->openFileList);
> > > +   INIT_LIST_HEAD(&ret_buf->tcon_list);
> > > +   spin_lock_init(&ret_buf->open_file_lock);
> > > +   mutex_init(&ret_buf->crfid.fid_mutex);
> > > +   spin_lock_init(&ret_buf->stat_lock);
> > > +   atomic_set(&ret_buf->num_local_opens, 0);
> > > +   atomic_set(&ret_buf->num_remote_opens, 0);
> > > +
> > >     return ret_buf;
> > >  }
> > >
>
>
>


-- 
Thanks,

Steve

View attachment "0001-cifs-check-kzalloc-return.patch" of type "text/x-patch" (2549 bytes)