Re: [PATCH 4.9 038/109] dmaengine: stm32-dma: Fix null pointer dereference in stm32_dma_tx_status

[Ludovic BARRE]

with Pierre Yves mail it's better ;-)

On 12/07/2017 02:04 PM, Ludovic BARRE wrote:
> add Pierre-yves Mordret
>
> acked-by: Ludovic BARRE <ludovic.barre@xxxxxx>
>
> On 12/07/2017 01:56 PM, Greg Kroah-Hartman wrote:
> > 4.9-stable review patch. If anyone has any objections, please let me 
> > know.
> >
> > ------------------
> >
> > From: M'boumba Cedric Madianga <cedric.madianga@xxxxxxxxx>
> >
> >
> > [ Upstream commit 57b5a32135c813f2ab669039fb4ec16b30cb3305 ]
> >
> > chan->desc is always set to NULL when a DMA transfer is complete.
> > As a DMA transfer could be complete during the call of 
> > stm32_dma_tx_status,
> > we need to be sure that chan->desc is not NULL before using this variable
> > to avoid a null pointer deference issue.
> >
> > Signed-off-by: M'boumba Cedric Madianga <cedric.madianga@xxxxxxxxx>
> > Reviewed-by: Ludovic BARRE <ludovic.barre@xxxxxx>
> > Signed-off-by: Vinod Koul <vinod.koul@xxxxxxxxx>
> > Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > ---
> > Â drivers/dma/stm32-dma.c |ÂÂ 10 +++-------
> > Â 1 file changed, 3 insertions(+), 7 deletions(-)
> >
> > --- a/drivers/dma/stm32-dma.c
> > +++ b/drivers/dma/stm32-dma.c
> > @@ -884,7 +884,7 @@ static enum dma_status stm32_dma_tx_stat
> > ÂÂÂÂÂ struct virt_dma_desc *vdesc;
> > ÂÂÂÂÂ enum dma_status status;
> > ÂÂÂÂÂ unsigned long flags;
> > -ÂÂÂ u32 residue;
> > +ÂÂÂ u32 residue = 0;
> > ÂÂÂÂÂ status = dma_cookie_status(c, cookie, state);
> > ÂÂÂÂÂ if ((status == DMA_COMPLETE) || (!state))
> > @@ -892,16 +892,12 @@ static enum dma_status stm32_dma_tx_stat
> > ÂÂÂÂÂ spin_lock_irqsave(&chan->vchan.lock, flags);
> > ÂÂÂÂÂ vdesc = vchan_find_desc(&chan->vchan, cookie);
> > -ÂÂÂ if (cookie == chan->desc->vdesc.tx.cookie) {
> > +ÂÂÂ if (chan->desc && cookie == chan->desc->vdesc.tx.cookie)
> > ÂÂÂÂÂÂÂÂÂ residue = stm32_dma_desc_residue(chan, chan->desc,
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ chan->next_sg);
> > -ÂÂÂ } else if (vdesc) {
> > +ÂÂÂ else if (vdesc)
> > ÂÂÂÂÂÂÂÂÂ residue = stm32_dma_desc_residue(chan,
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ to_stm32_dma_desc(vdesc), 0);
> > -ÂÂÂ } else {
> > -ÂÂÂÂÂÂÂ residue = 0;
> > -ÂÂÂ }
> > -
> > ÂÂÂÂÂ dma_set_residue(state, residue);
> > ÂÂÂÂÂ spin_unlock_irqrestore(&chan->vchan.lock, flags);