From: Xuan Zhuo <xuanzhuo@xxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxxxx>
Reported-by: Corentin Noël <corentin.noel@xxxxxxxxxxxxx>
Tested-by: Corentin Noël <corentin.noel@xxxxxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
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
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