linux-kernel - [PATCH v4] sfc: potential dereference null pointer of rx_queue->page

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Message-Id: <20211220023715.746815-1-jiasheng@iscas.ac.cn>
Date:   Mon, 20 Dec 2021 10:37:15 +0800
From:   Jiasheng Jiang <jiasheng@...as.ac.cn>
To:     ecree.xilinx@...il.com, habetsm.xilinx@...il.com,
        davem@...emloft.net, kuba@...nel.org, ast@...nel.org,
        daniel@...earbox.net, hawk@...nel.org, john.fastabend@...il.com,
        andrii@...nel.org, kafai@...com, songliubraving@...com, yhs@...com,
        kpsingh@...nel.org
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org, Jiasheng Jiang <jiasheng@...as.ac.cn>
Subject: [PATCH v4] sfc: potential dereference null pointer of rx_queue->page_ring

The return value of kcalloc() needs to be checked.
To avoid dereference of null pointer in case of the failure of alloc,
such as efx_fini_rx_recycle_ring().
Therefore, it should be better to change the definition of page_ptr_mask
to signed int and then assign the page_ptr_mask to -1 when page_ring is
NULL, in order to avoid the use in the loop.

Fixes: 5a6681e22c14 ("sfc: separate out SFC4000 ("Falcon") support into new sfc-falcon driver")
Signed-off-by: Jiasheng Jiang <jiasheng@...as.ac.cn>
---
Changelog:

v3 -> v4

*Change 1. Casade return -ENOMEM when alloc fails and deal with the
error.
*Change 2. Set size to -1 instead of return error.
*Change 3. Change the Fixes tag.
---
 drivers/net/ethernet/sfc/net_driver.h | 2 +-
 drivers/net/ethernet/sfc/rx_common.c  | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/sfc/net_driver.h b/drivers/net/ethernet/sfc/net_driver.h
index 9b4b25704271..beba3e0a6027 100644
--- a/drivers/net/ethernet/sfc/net_driver.h
+++ b/drivers/net/ethernet/sfc/net_driver.h
@@ -407,7 +407,7 @@ struct efx_rx_queue {
 	unsigned int page_recycle_count;
 	unsigned int page_recycle_failed;
 	unsigned int page_recycle_full;
-	unsigned int page_ptr_mask;
+	int page_ptr_mask;
 	unsigned int max_fill;
 	unsigned int fast_fill_trigger;
 	unsigned int min_fill;
diff --git a/drivers/net/ethernet/sfc/rx_common.c b/drivers/net/ethernet/sfc/rx_common.c
index 68fc7d317693..d9d0a5805f1c 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 = -1;
+	else
+		rx_queue->page_ptr_mask = page_ring_size - 1;
 }
 
 static void efx_fini_rx_recycle_ring(struct efx_rx_queue *rx_queue)
-- 
2.25.1