netdev - [PATCH net 02/11] igb: Fix use-after-free error during reset

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Message-Id: <20210701180420.346126-3-anthony.l.nguyen@intel.com>
Date:   Thu,  1 Jul 2021 11:04:11 -0700
From:   Tony Nguyen <anthony.l.nguyen@...el.com>
To:     davem@...emloft.net, kuba@...nel.org
Cc:     Vinicius Costa Gomes <vinicius.gomes@...el.com>,
        netdev@...r.kernel.org, anthony.l.nguyen@...el.com,
        Erez Geva <erez.geva.ext@...mens.com>,
        Tony Brelinski <tonyx.brelinski@...el.com>
Subject: [PATCH net 02/11] igb: Fix use-after-free error during reset

From: Vinicius Costa Gomes <vinicius.gomes@...el.com>

Cleans the next descriptor to watch (next_to_watch) when cleaning the
TX ring.

Failure to do so can cause invalid memory accesses. If igb_poll() runs
while the controller is reset this can lead to the driver try to free
a skb that was already freed.

(The crash is harder to reproduce with the igb driver, but the same
potential problem exists as the code is identical to igc)

Fixes: 7cc6fd4c60f2 ("igb: Don't bother clearing Tx buffer_info in igb_clean_tx_ring")
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@...el.com>
Reported-by: Erez Geva <erez.geva.ext@...mens.com>
Tested-by: Tony Brelinski <tonyx.brelinski@...el.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
---
 drivers/net/ethernet/intel/igb/igb_main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index 7e6435dc7e80..a61e2e5e95c0 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -4835,6 +4835,8 @@ static void igb_clean_tx_ring(struct igb_ring *tx_ring)
 					       DMA_TO_DEVICE);
 		}
 
+		tx_buffer->next_to_watch = NULL;
+
 		/* move us one more past the eop_desc for start of next pkt */
 		tx_buffer++;
 		i++;
-- 
2.26.2