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Subject[PATCH][net-next] iavf: fix dereference of null rx_buffer pointer
Date
From: Colin Ian King <colin.king@canonical.com>

A recent commit efa14c3985828d ("iavf: allow null RX descriptors") added
a null pointer sanity check on rx_buffer, however, rx_buffer is being
dereferenced before that check, which implies a null pointer dereference
bug can potentially occur. Fix this by only dereferencing rx_buffer
until after the null pointer check.

Addresses-Coverity: ("Dereference before null check")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
drivers/net/ethernet/intel/iavf/iavf_txrx.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/intel/iavf/iavf_txrx.c b/drivers/net/ethernet/intel/iavf/iavf_txrx.c
index 1cde1601bc32..0cca1b589b56 100644
--- a/drivers/net/ethernet/intel/iavf/iavf_txrx.c
+++ b/drivers/net/ethernet/intel/iavf/iavf_txrx.c
@@ -1296,7 +1296,7 @@ static struct sk_buff *iavf_construct_skb(struct iavf_ring *rx_ring,
struct iavf_rx_buffer *rx_buffer,
unsigned int size)
{
- void *va = page_address(rx_buffer->page) + rx_buffer->page_offset;
+ void *va;
#if (PAGE_SIZE < 8192)
unsigned int truesize = iavf_rx_pg_size(rx_ring) / 2;
#else
@@ -1308,6 +1308,7 @@ static struct sk_buff *iavf_construct_skb(struct iavf_ring *rx_ring,
if (!rx_buffer)
return NULL;
/* prefetch first cache line of first page */
+ va = page_address(rx_buffer->page) + rx_buffer->page_offset;
prefetch(va);
#if L1_CACHE_BYTES < 128
prefetch(va + L1_CACHE_BYTES);
@@ -1362,7 +1363,7 @@ static struct sk_buff *iavf_build_skb(struct iavf_ring *rx_ring,
struct iavf_rx_buffer *rx_buffer,
unsigned int size)
{
- void *va = page_address(rx_buffer->page) + rx_buffer->page_offset;
+ void *va;
#if (PAGE_SIZE < 8192)
unsigned int truesize = iavf_rx_pg_size(rx_ring) / 2;
#else
@@ -1374,6 +1375,7 @@ static struct sk_buff *iavf_build_skb(struct iavf_ring *rx_ring,
if (!rx_buffer)
return NULL;
/* prefetch first cache line of first page */
+ va = page_address(rx_buffer->page) + rx_buffer->page_offset;
prefetch(va);
#if L1_CACHE_BYTES < 128
prefetch(va + L1_CACHE_BYTES);
--
2.20.1
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