[PATCH] vmxnet3: fix lock imbalance in vmxnet3_tq_xmit()

[PATCH] vmxnet3: fix lock imbalance in vmxnet3_tq_xmit()

[Arnd Bergmann]

A recent bug fix rearranged the code in vmxnet3_tq_xmit() in a
way that left the error handling for oversized headers unlock
a lock that had not been taken yet. Gcc warns about the incorrect
use of the 'flags' variable because of that:

drivers/net/vmxnet3/vmxnet3_drv.c: In function 'vmxnet3_tq_xmit.constprop':
include/linux/spinlock.h:246:3: error: 'flags' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This changes the error handling path to 'goto' the end of the function
beyond the lock/unlock pair.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: cec05562fb1d ("vmxnet3: avoid calling pskb_may_pull with interrupts disabled")
---
 drivers/net/vmxnet3/vmxnet3_drv.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/vmxnet3/vmxnet3_drv.c b/drivers/net/vmxnet3/vmxnet3_drv.c
index fc895d0e85d9..b2348f67b00a 100644
--- a/drivers/net/vmxnet3/vmxnet3_drv.c
+++ b/drivers/net/vmxnet3/vmxnet3_drv.c
@@ -1022,14 +1022,16 @@ vmxnet3_tq_xmit(struct sk_buff *skb, struct vmxnet3_tx_queue *tq,
 		if (ctx.mss) {
 			if (unlikely(ctx.eth_ip_hdr_size + ctx.l4_hdr_size >
 				     VMXNET3_MAX_TX_BUF_SIZE)) {
-				goto hdr_too_big;
+				tq->stats.drop_oversized_hdr++;
+				goto drop_pkt;
 			}
 		} else {
 			if (skb->ip_summed == CHECKSUM_PARTIAL) {
 				if (unlikely(ctx.eth_ip_hdr_size +
 					     skb->csum_offset >
 					     VMXNET3_MAX_CSUM_OFFSET)) {
-					goto hdr_too_big;
+					tq->stats.drop_oversized_hdr++;
+					goto drop_pkt;
 				}
 			}
 		}
@@ -1123,8 +1125,6 @@ vmxnet3_tq_xmit(struct sk_buff *skb, struct vmxnet3_tx_queue *tq,
 
 	return NETDEV_TX_OK;
 
-hdr_too_big:
-	tq->stats.drop_oversized_hdr++;
 unlock_drop_pkt:
 	spin_unlock_irqrestore(&tq->tx_lock, flags);
 drop_pkt:
-- 
2.7.0

Re: [PATCH] vmxnet3: fix lock imbalance in vmxnet3_tq_xmit()

[David Miller]

From: Arnd Bergmann <arnd@arndb.de>
Date: Mon, 14 Mar 2016 15:53:57 +0100

> A recent bug fix rearranged the code in vmxnet3_tq_xmit() in a
> way that left the error handling for oversized headers unlock
> a lock that had not been taken yet. Gcc warns about the incorrect
> use of the 'flags' variable because of that:
> 
> drivers/net/vmxnet3/vmxnet3_drv.c: In function 'vmxnet3_tq_xmit.constprop':
> include/linux/spinlock.h:246:3: error: 'flags' may be used uninitialized in this function [-Werror=maybe-uninitialized]
> 
> This changes the error handling path to 'goto' the end of the function
> beyond the lock/unlock pair.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Fixes: cec05562fb1d ("vmxnet3: avoid calling pskb_may_pull with interrupts disabled")

Applied and queued up for -stable, thanks.