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* [PATCH net] virtio-net: fix for skb_over_panic inside big mode
@ 2021-10-09  9:17 ` Michael S. Tsirkin
  0 siblings, 0 replies; 16+ messages in thread
From: Michael S. Tsirkin @ 2021-10-09  9:17 UTC (permalink / raw)
  To: linux-kernel
  Cc: Xuan Zhuo, Greg KH, Corentin Noël, Jason Wang,
	David S. Miller, Jakub Kicinski, virtualization, netdev

From: Xuan Zhuo <xuanzhuo@linux.alibaba.com>

commit 126285651b7f ("Merge ra.kernel.org:/pub/scm/linux/kernel/git/netdev/net")
accidentally reverted the effect of
commit 1a8024239da ("virtio-net: fix for skb_over_panic inside big mode")
on drivers/net/virtio_net.c

As a result, users of crosvm (which is using large packet mode)
are experiencing crashes with 5.14-rc1 and above that do not
occur with 5.13.

Crash trace:

[   61.346677] skbuff: skb_over_panic: text:ffffffff881ae2c7 len:3762 put:3762 head:ffff8a5ec8c22000 data:ffff8a5ec8c22010 tail:0xec2 end:0xec0 dev:<NULL>
[   61.369192] kernel BUG at net/core/skbuff.c:111!
[   61.372840] invalid opcode: 0000 [#1] SMP PTI
[   61.374892] CPU: 5 PID: 0 Comm: swapper/5 Not tainted 5.14.0-rc1 linux-v5.14-rc1-for-mesa-ci.tar.bz2 #1
[   61.376450] Hardware name: ChromiumOS crosvm, BIOS 0

..

[   61.393635] Call Trace:
[   61.394127]  <IRQ>
[   61.394488]  skb_put.cold+0x10/0x10
[   61.395095]  page_to_skb+0xf7/0x410
[   61.395689]  receive_buf+0x81/0x1660
[   61.396228]  ? netif_receive_skb_list_internal+0x1ad/0x2b0
[   61.397180]  ? napi_gro_flush+0x97/0xe0
[   61.397896]  ? detach_buf_split+0x67/0x120
[   61.398573]  virtnet_poll+0x2cf/0x420
[   61.399197]  __napi_poll+0x25/0x150
[   61.399764]  net_rx_action+0x22f/0x280
[   61.400394]  __do_softirq+0xba/0x257
[   61.401012]  irq_exit_rcu+0x8e/0xb0
[   61.401618]  common_interrupt+0x7b/0xa0
[   61.402270]  </IRQ>

See
https://lore.kernel.org/r/5edaa2b7c2fe4abd0347b8454b2ac032b6694e2c.camel%40collabora.com
for the report.

Apply the original 1a8024239da ("virtio-net: fix for skb_over_panic inside big mode")
again, the original logic still holds:

In virtio-net's large packet mode, there is a hole in the space behind
buf.

    hdr_padded_len - hdr_len

We must take this into account when calculating tailroom.

Cc: Greg KH <gregkh@linuxfoundation.org>
Fixes: fb32856b16ad ("virtio-net: page_to_skb() use build_skb when there's sufficient tailroom")
Fixes: 126285651b7f ("Merge ra.kernel.org:/pub/scm/linux/kernel/git/netdev/net")
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Reported-by: Corentin Noël <corentin.noel@collabora.com>
Tested-by: Corentin Noël <corentin.noel@collabora.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---

David, I think we need this in stable, too.

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

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 096c2ac6b7a6..6b0812f44bbf 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -406,7 +406,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
 	 * add_recvbuf_mergeable() + get_mergeable_buf_len()
 	 */
 	truesize = headroom ? PAGE_SIZE : truesize;
-	tailroom = truesize - len - headroom;
+	tailroom = truesize - len - headroom - (hdr_padded_len - hdr_len);
 	buf = p - headroom;
 
 	len -= hdr_len;
-- 
MST


^ permalink raw reply related	[flat|nested] 16+ messages in thread
* [PATCH net] virtio-net: fix for skb_over_panic inside big mode
@ 2021-06-03 17:09 ` Xuan Zhuo
  0 siblings, 0 replies; 16+ messages in thread
From: Xuan Zhuo @ 2021-06-03 17:09 UTC (permalink / raw)
  To: netdev
  Cc: Michael S. Tsirkin, Jason Wang, David S. Miller, Jakub Kicinski,
	Xuan Zhuo, virtualization, Corentin Noël

In virtio-net's large packet mode, there is a hole in the space behind
buf.

    hdr_padded_len - hdr_len

We must take this into account when calculating tailroom.

[   44.544385] skb_put.cold (net/core/skbuff.c:5254 (discriminator 1) net/core/skbuff.c:5252 (discriminator 1))
[   44.544864] page_to_skb (drivers/net/virtio_net.c:485) [   44.545361] receive_buf (drivers/net/virtio_net.c:849 drivers/net/virtio_net.c:1131)
[   44.545870] ? netif_receive_skb_list_internal (net/core/dev.c:5714)
[   44.546628] ? dev_gro_receive (net/core/dev.c:6103)
[   44.547135] ? napi_complete_done (./include/linux/list.h:35 net/core/dev.c:5867 net/core/dev.c:5862 net/core/dev.c:6565)
[   44.547672] virtnet_poll (drivers/net/virtio_net.c:1427 drivers/net/virtio_net.c:1525)
[   44.548251] __napi_poll (net/core/dev.c:6985)
[   44.548744] net_rx_action (net/core/dev.c:7054 net/core/dev.c:7139)
[   44.549264] __do_softirq (./arch/x86/include/asm/jump_label.h:19 ./include/linux/jump_label.h:200 ./include/trace/events/irq.h:142 kernel/softirq.c:560)
[   44.549762] irq_exit_rcu (kernel/softirq.c:433 kernel/softirq.c:637 kernel/softirq.c:649)
[   44.551384] common_interrupt (arch/x86/kernel/irq.c:240 (discriminator 13))
[   44.551991] ? asm_common_interrupt (./arch/x86/include/asm/idtentry.h:638)
[   44.552654] asm_common_interrupt (./arch/x86/include/asm/idtentry.h:638)

Fixes: fb32856b16ad ("virtio-net: page_to_skb() use build_skb when there's sufficient tailroom")
Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Reported-by: Corentin Noël <corentin.noel@collabora.com>
Tested-by: Corentin Noël <corentin.noel@collabora.com>
---
 drivers/net/virtio_net.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index fa407eb8b457..78a01c71a17c 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -406,7 +406,7 @@ static struct sk_buff *page_to_skb(struct virtnet_info *vi,
 	 * add_recvbuf_mergeable() + get_mergeable_buf_len()
 	 */
 	truesize = headroom ? PAGE_SIZE : truesize;
-	tailroom = truesize - len - headroom;
+	tailroom = truesize - len - headroom - (hdr_padded_len - hdr_len);
 	buf = p - headroom;
 
 	len -= hdr_len;
-- 
2.31.0


^ permalink raw reply related	[flat|nested] 16+ messages in thread

end of thread, other threads:[~2021-10-11  2:05 UTC | newest]

Thread overview: 16+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-10-09  9:17 [PATCH net] virtio-net: fix for skb_over_panic inside big mode Michael S. Tsirkin
2021-10-09  9:17 ` Michael S. Tsirkin
2021-10-09  9:29 ` Xuan Zhuo
2021-10-11  2:04 ` Jason Wang
2021-10-11  2:04   ` Jason Wang
  -- strict thread matches above, loose matches on Subject: below --
2021-06-03 17:09 Xuan Zhuo
2021-06-03 17:09 ` Xuan Zhuo
2021-06-03 22:30 ` patchwork-bot+netdevbpf
2021-06-04  2:28 ` Jason Wang
2021-06-04  2:28   ` Jason Wang
2021-06-04  2:30   ` Xuan Zhuo
2021-06-04  3:00     ` Jason Wang
2021-06-04  3:00       ` Jason Wang
2021-06-04  3:05       ` Xuan Zhuo
2021-06-04  6:00         ` Jason Wang
2021-06-04  6:00           ` Jason Wang

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