diff mbox series

[5.10,26/76] sfc: Check null pointer of rx_queue->page_ring

Message ID 20211227151325.595242432@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg Kroah-Hartman Dec. 27, 2021, 3:30 p.m. UTC 
From: Jiasheng Jiang <jiasheng@iscas.ac.cn>

[ Upstream commit bdf1b5c3884f6a0dc91b0dbdb8c3b7d205f449e0 ]

Because of the possible failure of the kcalloc, it should be better to
set rx_queue->page_ptr_mask to 0 when it happens in order to maintain
the consistency.

Fixes: 5a6681e22c14 ("sfc: separate out SFC4000 ("Falcon") support into new sfc-falcon driver")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Acked-by: Martin Habets <habetsm.xilinx@gmail.com>
Link: https://lore.kernel.org/r/20211220135603.954944-1-jiasheng@iscas.ac.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/net/ethernet/sfc/rx_common.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Comments

Martin Habets Jan. 1, 2022, 11:54 a.m. UTC | #1 
On Wed, Dec 29, 2021 at 12:17:30PM +0100, Pavel Machek wrote:
> hi!
> 
> > From: Jiasheng Jiang <jiasheng@iscas.ac.cn>
> > 
> > [ Upstream commit bdf1b5c3884f6a0dc91b0dbdb8c3b7d205f449e0 ]
> > 
> > Because of the possible failure of the kcalloc, it should be better to
> > set rx_queue->page_ptr_mask to 0 when it happens in order to maintain
> > the consistency.
> 
> This is confusing/wrong, or at least not a complete fix.
> 
> > +++ b/drivers/net/ethernet/sfc/rx_common.c
> > @@ -150,7 +150,10 @@ static void efx_init_rx_recycle_ring(struct efx_rx_queue *rx_queue)
> >  					    efx->rx_bufs_per_page);
> >  	rx_queue->page_ring = kcalloc(page_ring_size,
> >  				      sizeof(*rx_queue->page_ring), GFP_KERNEL);
> > -	rx_queue->page_ptr_mask = page_ring_size - 1;
> > +	if (!rx_queue->page_ring)
> > +		rx_queue->page_ptr_mask = 0;
> > +	else
> > +		rx_queue->page_ptr_mask = page_ring_size - 1;
> >  }
> >  
> 
> So we have !rx_queue->page_ring. But in efx_reuse_page, we do
> 
>         index = rx_queue->page_remove & rx_queue->page_ptr_mask;
> 	page = rx_queue->page_ring[index];
> 
> So index is now zero, but we'll derefernce null pointer anyway.

Good point. I've posted a patch for this to netdev.
https://lore.kernel.org/netdev/164103678041.26263.8354809911405746465.stgit@palantir17.mph.net/

Thanks,
Martin
diff mbox series

Patch

diff --git a/drivers/net/ethernet/sfc/rx_common.c b/drivers/net/ethernet/sfc/rx_common.c
index 19cf7cac1e6e9..8834bcb12fa97 100644
--- a/drivers/net/ethernet/sfc/rx_common.c
+++ b/drivers/net/ethernet/sfc/rx_common.c
@@ -150,7 +150,10 @@  static void efx_init_rx_recycle_ring(struct efx_rx_queue *rx_queue)
 					    efx->rx_bufs_per_page);
 	rx_queue->page_ring = kcalloc(page_ring_size,
 				      sizeof(*rx_queue->page_ring), GFP_KERNEL);
-	rx_queue->page_ptr_mask = page_ring_size - 1;
+	if (!rx_queue->page_ring)
+		rx_queue->page_ptr_mask = 0;
+	else
+		rx_queue->page_ptr_mask = page_ring_size - 1;
 }
 
 static void efx_fini_rx_recycle_ring(struct efx_rx_queue *rx_queue)