From: Christoph Paasch <cpaasch@xxxxxxxxx>
syzkaller is not happy since commit fdfc5c8594c2 ("tcp: remove empty skb
from write queue in error cases"):
CPU: 1 PID: 13814 Comm: syz-executor.4 Not tainted 4.14.143 #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.5.1 01/01/2011
task: ffff888040105c00 task.stack: ffff8880649c0000
RIP: 0010:tcp_sendmsg_locked+0x6b4/0x4390 net/ipv4/tcp.c:1350
RSP: 0018:ffff8880649cf718 EFLAGS: 00010206
RAX: 0000000000000014 RBX: 000000000000001e RCX: ffffc90000717000
RDX: 0000000000000077 RSI: ffffffff82e760f7 RDI: 00000000000000a0
RBP: ffff8880649cfaa8 R08: 1ffff1100c939e7a R09: ffff8880401063c8
R10: 0000000000000003 R11: 0000000000000001 R12: dffffc0000000000
R13: ffff888043d74750 R14: ffff888043d74500 R15: 000000000000001e
FS: 00007f0afcb6d700(0000) GS:ffff88806cf00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2ca22000 CR3: 0000000040496004 CR4: 00000000003606e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
tcp_sendmsg+0x2a/0x40 net/ipv4/tcp.c:1533
inet_sendmsg+0x173/0x4e0 net/ipv4/af_inet.c:784
sock_sendmsg_nosec net/socket.c:646 [inline]
sock_sendmsg+0xc3/0x100 net/socket.c:656
SYSC_sendto+0x35d/0x5e0 net/socket.c:1766
do_syscall_64+0x241/0x680 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
The problem is that we are removing an skb from the write-queue that
could have been referenced by the sk_send_head. Thus, we need to check
for the send_head's sanity after removing it.
This patch needs to be backported only to 4.14 and older (among those
that applied the backport of fdfc5c8594c2).
Fixes: fdfc5c8594c2 ("tcp: remove empty skb from write queue in error cases")
Cc: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Jason Baron <jbaron@xxxxxxxxxx>
Cc: Vladimir Rutsky <rutsky@xxxxxxxxxx>
Cc: Soheil Hassas Yeganeh <soheil@xxxxxxxxxx>
Cc: Neal Cardwell <ncardwell@xxxxxxxxxx>
Signed-off-by: Christoph Paasch <cpaasch@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
net/ipv4/tcp.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -924,8 +924,7 @@ static void tcp_remove_empty_skb(struct
{
if (skb && !skb->len) {
tcp_unlink_write_queue(skb, sk);
- if (tcp_write_queue_empty(sk))
- tcp_chrono_stop(sk, TCP_CHRONO_BUSY);
+ tcp_check_send_head(sk, skb);
sk_wmem_free_skb(sk, skb);
}
}
