linux-kernel - Re: [PATCH v2] dma-buf: acquire name lock before read/write dma

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Date:   Tue, 12 Oct 2021 17:07:55 +0800
From:   <guangming.cao@...iatek.com>
To:     <christian.koenig@....com>
CC:     <dri-devel@...ts.freedesktop.org>, <guangming.cao@...iatek.com>,
        <linaro-mm-sig@...ts.linaro.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-media@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <matthias.bgg@...il.com>,
        <sumit.semwal@...aro.org>, <wsd_upstream@...iatek.com>,
        Guangming Cao <Guangming.Cao@...iatek.com>
Subject: Re: [PATCH v2] dma-buf: acquire name lock before read/write dma_buf.name

From: Guangming Cao <Guangming.Cao@...iatek.com>

> Am 08.10.21 um 09:54 schrieb guangming.cao@...iatek.com:
> > From: Guangming Cao <Guangming.Cao@...iatek.com>
> >
> > Because dma-buf.name can be freed in func: "dma_buf_set_name",
> > so, we need to acquire lock first before we read/write dma_buf.name
> > to prevent Use After Free(UAF) issue.
> >
> > Signed-off-by: Guangming Cao <Guangming.Cao@...iatek.com>
> 
> Reviewed-by: Christian König <christian.koenig@....com>
> 
> Going to push that upstream if nobody else objects.
> 
> Thanks,
> Christian.

I'm sorry to disturb you, actually I need this patch to solve our issues.
Is there any question about it? seems it hasn't been merged into mainline.

Thanks,
Guangming.
> 
> > ---
> >   drivers/dma-buf/dma-buf.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> > index 511fe0d217a0..a7f6fd13a635 100644
> > --- a/drivers/dma-buf/dma-buf.c
> > +++ b/drivers/dma-buf/dma-buf.c
> > @@ -1372,6 +1372,8 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
> >   		if (ret)
> >   			goto error_unlock;
> >   
> > +
> > +		spin_lock(&buf_obj->name_lock);
> >   		seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
> >   				buf_obj->size,
> >   				buf_obj->file->f_flags, buf_obj->file->f_mode,
> > @@ -1379,6 +1381,7 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
> >   				buf_obj->exp_name,
> >   				file_inode(buf_obj->file)->i_ino,
> >   				buf_obj->name ?: "");
> > +		spin_unlock(&buf_obj->name_lock);
> >   
> >   		robj = buf_obj->resv;
> >   		fence = dma_resv_excl_fence(robj);