From: Cezar Bulinaru cbulinaru@gmail.com
commit 4f61f133f354853bc394ec7d6028adb9b02dd701 upstream.
Fixes a NULL pointer derefence bug triggered from tap driver. When tap_get_user calls virtio_net_hdr_to_skb the skb->dev is null (in tap.c skb->dev is set after the call to virtio_net_hdr_to_skb) virtio_net_hdr_to_skb calls dev_parse_header_protocol which needs skb->dev field to be valid.
The line that trigers the bug is in dev_parse_header_protocol (dev is at offset 0x10 from skb and is stored in RAX register) if (!dev->header_ops || !dev->header_ops->parse_protocol) 22e1: mov 0x10(%rbx),%rax 22e5: mov 0x230(%rax),%rax
Setting skb->dev before the call in tap.c fixes the issue.
BUG: kernel NULL pointer dereference, address: 0000000000000230 RIP: 0010:virtio_net_hdr_to_skb.constprop.0+0x335/0x410 [tap] Code: c0 0f 85 b7 fd ff ff eb d4 41 39 c6 77 cf 29 c6 48 89 df 44 01 f6 e8 7a 79 83 c1 48 85 c0 0f 85 d9 fd ff ff eb b7 48 8b 43 10 <48> 8b 80 30 02 00 00 48 85 c0 74 55 48 8b 40 28 48 85 c0 74 4c 48 RSP: 0018:ffffc90005c27c38 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff888298f25300 RCX: 0000000000000010 RDX: 0000000000000005 RSI: ffffc90005c27cb6 RDI: ffff888298f25300 RBP: ffffc90005c27c80 R08: 00000000ffffffea R09: 00000000000007e8 R10: ffff88858ec77458 R11: 0000000000000000 R12: 0000000000000001 R13: 0000000000000014 R14: ffffc90005c27e08 R15: ffffc90005c27cb6 FS: 0000000000000000(0000) GS:ffff88858ec40000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000230 CR3: 0000000281408006 CR4: 00000000003706e0 Call Trace: tap_get_user+0x3f1/0x540 [tap] tap_sendmsg+0x56/0x362 [tap] ? get_tx_bufs+0xc2/0x1e0 [vhost_net] handle_tx_copy+0x114/0x670 [vhost_net] handle_tx+0xb0/0xe0 [vhost_net] handle_tx_kick+0x15/0x20 [vhost_net] vhost_worker+0x7b/0xc0 [vhost] ? vhost_vring_call_reset+0x40/0x40 [vhost] kthread+0xfa/0x120 ? kthread_complete_and_exit+0x20/0x20 ret_from_fork+0x1f/0x30
Fixes: 924a9bc362a5 ("net: check if protocol extracted by virtio_net_hdr_set_proto is correct") Signed-off-by: Cezar Bulinaru cbulinaru@gmail.com Reviewed-by: Willem de Bruijn willemb@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/tap.c | 20 +++++++++++--------- 1 file changed, 11 insertions(+), 9 deletions(-)
--- a/drivers/net/tap.c +++ b/drivers/net/tap.c @@ -716,10 +716,20 @@ static ssize_t tap_get_user(struct tap_q skb_reset_mac_header(skb); skb->protocol = eth_hdr(skb)->h_proto;
+ rcu_read_lock(); + tap = rcu_dereference(q->tap); + if (!tap) { + kfree_skb(skb); + rcu_read_unlock(); + return total_len; + } + skb->dev = tap->dev; + if (vnet_hdr_len) { err = virtio_net_hdr_to_skb(skb, &vnet_hdr, tap_is_little_endian(q)); if (err) { + rcu_read_unlock(); drop_reason = SKB_DROP_REASON_DEV_HDR; goto err_kfree; } @@ -732,8 +742,6 @@ static ssize_t tap_get_user(struct tap_q __vlan_get_protocol(skb, skb->protocol, &depth) != 0) skb_set_network_header(skb, depth);
- rcu_read_lock(); - tap = rcu_dereference(q->tap); /* copy skb_ubuf_info for callback when skb has no error */ if (zerocopy) { skb_zcopy_init(skb, msg_control); @@ -742,14 +750,8 @@ static ssize_t tap_get_user(struct tap_q uarg->callback(NULL, uarg, false); }
- if (tap) { - skb->dev = tap->dev; - dev_queue_xmit(skb); - } else { - kfree_skb(skb); - } + dev_queue_xmit(skb); rcu_read_unlock(); - return total_len;
err_kfree: