xen/netfront: tolerate frags with no data

PATCH In review Juergen Gross 2 participants 5 messages Dec 18, 2018 – Dec 19, 2018

Subsystems (4)

Networking Network drivers Stable branch Xen hypervisor interface

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Juergen Gross

author maintainer

2018-12-18 15:06 UTC #0 lore raw

PATCH 1/1 xen/netfront: tolerate frags with no data

At least old Xen net backends seem to send frags with no real data sometimes. In case such a fragment happens to occur with the frag limit already reached the frontend will BUG currently even if this situation is easily recoverable.

Modify the BUG_ON() condition accordingly.

Cc [email protected]

Tested-by Dietmar Hahn <[email protected]>

Signed-off-by Juergen Gross <[email protected]>

---
 drivers/net/xen-netfront.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

drivers/net/xen-netfront.c +1 -1

index f17f602e6171..5b97cc946d70 100644
@@ -905,7 +905,7 @@ static RING_IDX xennet_fill_frags(struct netfront_queue *queue,
 		if (skb_shinfo(skb)->nr_frags == MAX_SKB_FRAGS) {
 			unsigned int pull_to = NETFRONT_SKB_CB(skb)->pull_to;
 
-			BUG_ON(pull_to <= skb_headlen(skb));
+			BUG_ON(pull_to < skb_headlen(skb));
 			__pskb_pull_tail(skb, pull_to - skb_headlen(skb));
 		}
 		if (unlikely(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS)) {

Signature · 1 line

2.16.4

David Miller

maintainer

2018-12-19 06:00 UTC #1 lore raw

From: Juergen Gross <[email protected]>
Date: Tue, 18 Dec 2018 16:06:19 +0100

Quoted 9 lines

At least old Xen net backends seem to send frags with no real data sometimes. In case such a fragment happens to occur with the frag limit already reached the frontend will BUG currently even if this situation is easily recoverable.
Modify the BUG_ON() condition accordingly.
Tested-by Dietmar Hahn <[email protected]>
Signed-off-by Juergen Gross <[email protected]>

Applied and queued up for -stable.

But many of these BUG's in the driver should be converted to WARNs and recovery code added.

Juergen Gross

author maintainer

2018-12-19 06:02 UTC #2 lore raw

Quoted 10 lines · David Miller

From: Juergen Gross <[email protected]>
Date: Tue, 18 Dec 2018 16:06:19 +0100
Quoted 7 lines
At least old Xen net backends seem to send frags with no real data sometimes. In case such a fragment happens to occur with the frag limit already reached the frontend will BUG currently even if this situation is easily recoverable.
Modify the BUG_ON() condition accordingly.

Quoted 8 lines

Quoted 2 lines
Tested-by Dietmar Hahn <[email protected]>
Signed-off-by Juergen Gross <[email protected]>
Applied and queued up for -stable.
But many of these BUG's in the driver should be converted to WARNs and recovery code added.

Right, but that will be no stable material then. Will start that effort after Christmas.

Juergen

Juergen Gross

author maintainer

2018-12-19 06:02 UTC #3 lore raw

In reply to David Miller

Quoted 10 lines · David Miller

From: Juergen Gross <[email protected]>
Date: Tue, 18 Dec 2018 16:06:19 +0100
Quoted 7 lines
At least old Xen net backends seem to send frags with no real data sometimes. In case such a fragment happens to occur with the frag limit already reached the frontend will BUG currently even if this situation is easily recoverable.
Modify the BUG_ON() condition accordingly.

Quoted 8 lines

Quoted 2 lines
Tested-by Dietmar Hahn <[email protected]>
Signed-off-by Juergen Gross <[email protected]>
Applied and queued up for -stable.
But many of these BUG's in the driver should be converted to WARNs and recovery code added.

Right, but that will be no stable material then. Will start that effort after Christmas.

Juergen

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Xen-devel mailing list
[email protected]
https://lists.xenproject.org/mailman/listinfo/xen-devel

David Miller

maintainer

2018-12-19 06:00 UTC #4 lore raw

In reply to Juergen Gross

From: Juergen Gross <[email protected]>
Date: Tue, 18 Dec 2018 16:06:19 +0100

Quoted 9 lines

At least old Xen net backends seem to send frags with no real data sometimes. In case such a fragment happens to occur with the frag limit already reached the frontend will BUG currently even if this situation is easily recoverable.
Modify the BUG_ON() condition accordingly.
Tested-by Dietmar Hahn <[email protected]>
Signed-off-by Juergen Gross <[email protected]>

Applied and queued up for -stable.

But many of these BUG's in the driver should be converted to WARNs and recovery code added.

_______________________________________________
Xen-devel mailing list
[email protected]
https://lists.xenproject.org/mailman/listinfo/xen-devel