[PATCH] net: xdp: fix error return code of xsk_generic_xmit()

[Jia-Ju Bai]

When err is zero but xskq_prod_reserve() fails, no error return code of
xsk_generic_xmit() is assigned.
To fix this bug, err is assigned with the return value of
xskq_prod_reserve(), and then err is checked.
The spinlock is only used to protect the call to xskq_prod_reserve().

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>
Signed-off-by: Jia-Ju Bai <baijiaju1990@xxxxxxxxx>
---
 net/xdp/xsk.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 4faabd1ecfd1..f1c1db07dd07 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -484,8 +484,14 @@ static int xsk_generic_xmit(struct sock *sk)
 		 * if there is space in it. This avoids having to implement
 		 * any buffering in the Tx path.
 		 */
+		if (unlikely(err)) {
+			kfree_skb(skb);
+			goto out;
+		}
+
 		spin_lock_irqsave(&xs->pool->cq_lock, flags);
-		if (unlikely(err) || xskq_prod_reserve(xs->pool->cq)) {
+		err = xskq_prod_reserve(xs->pool->cq);
+		if (unlikely(err)) {
 			spin_unlock_irqrestore(&xs->pool->cq_lock, flags);
 			kfree_skb(skb);
 			goto out;
-- 
2.17.1