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authorCezar Bulinaru <cbulinaru@gmail.com>2022-08-03 02:27:59 -0400
committerDavid S. Miller <davem@davemloft.net>2022-08-05 08:56:35 +0100
commit4f61f133f354853bc394ec7d6028adb9b02dd701 (patch)
tree1cac827b4372531fdb987f42d594c1815576baed /drivers/net/tap.c
parent9f05f9ade27f1802d1305abd58c3e4a0d819deef (diff)
net: tap: NULL pointer derefence in dev_parse_header_protocol when skb->dev is null
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>
Diffstat (limited to 'drivers/net/tap.c')
-rw-r--r--drivers/net/tap.c20
1 files changed, 11 insertions, 9 deletions
diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index c3d42062559d..9e75ed3f08ce 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -716,10 +716,20 @@ static ssize_t tap_get_user(struct tap_queue *q, void *msg_control,
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_queue *q, void *msg_control,
__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_queue *q, void *msg_control,
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: