wifi: ath9k_htc: Use __skb_set_length() for resetting urb before resubmit

[ Upstream commit 94745807f3ebd379f23865e6dab196f220664179 ]

Syzbot points out that skb_trim() has a sanity check on the existing length of
the skb, which can be uninitialised in some error paths. The intent here is
clearly just to reset the length to zero before resubmitting, so switch to
calling __skb_set_length(skb, 0) directly. In addition, __skb_set_length()
already contains a call to skb_reset_tail_pointer(), so remove the redundant
call.

The syzbot report came from ath9k_hif_usb_reg_in_cb(), but there's a similar
usage of skb_trim() in ath9k_hif_usb_rx_cb(), change both while we're at it.

Reported-by: syzbot+98afa303be379af6cdb2@syzkaller.appspotmail.com
Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://patch.msgid.link/20240812142447.12328-1-toke@toke.dk
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/net/wireless/ath/ath9k/hif_usb.c b/drivers/net/wireless/ath/ath9k/hif_usb.c
index e0130beb304dfe2d4f231d57f043a0802543e87f..6c73c0c0b82a9909100c97148588d103d5a022f3 100644 (file)
--- a/drivers/net/wireless/ath/ath9k/hif_usb.c
+++ b/drivers/net/wireless/ath/ath9k/hif_usb.c
@@ -718,8 +718,7 @@ static void ath9k_hif_usb_rx_cb(struct urb *urb)
        }
 
 resubmit:
-       skb_reset_tail_pointer(skb);
-       skb_trim(skb, 0);
+       __skb_set_length(skb, 0);
 
        usb_anchor_urb(urb, &hif_dev->rx_submitted);
        ret = usb_submit_urb(urb, GFP_ATOMIC);
@@ -756,8 +755,7 @@ static void ath9k_hif_usb_reg_in_cb(struct urb *urb)
        case -ESHUTDOWN:
                goto free_skb;
        default:
-               skb_reset_tail_pointer(skb);
-               skb_trim(skb, 0);
+               __skb_set_length(skb, 0);
 
                goto resubmit;
        }