From 732b74d647048668f0f8dc0c848f0746c69e2e2f Mon Sep 17 00:00:00 2001 From: Xuan Zhuo Date: Sat, 9 Oct 2021 05:17:53 -0400 Subject: [PATCH] virtio-net: fix for skb_over_panic inside big mode MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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: [ 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] [ 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] 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 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 Reported-by: Corentin Noël Tested-by: Corentin Noël Signed-off-by: Michael S. Tsirkin Signed-off-by: David S. Miller --- 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 79bd2585ec6b..4ad25a8b0870 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;