netdev - Re: WARNING in tcp

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Date:	Wed, 25 Nov 2015 11:37:05 -0800
From:	Eric Dumazet <edumazet@...gle.com>
To:	Dmitry Vyukov <dvyukov@...gle.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>
Subject: Re: WARNING in tcp_recvmsg

On Wed, Nov 25, 2015 at 8:36 AM, Dmitry Vyukov <dvyukov@...gle.com> wrote:
> Hello,
>
> The following program triggers WARNING in tcp_recvmsg:
>
> // autogenerated by syzkaller (http://github.com/google/syzkaller)
> #include <syscall.h>
> #include <string.h>
> #include <stdint.h>
> #include <pthread.h>
> #include <sys/types.h>
> #include <sys/socket.h>
> #include <netinet/ip.h>
> #include <netinet/tcp.h>
>
> int fd = -1;
>
> void *thr0(void *arg)
> {
>         memcpy((void*)0x20003000,
> "\xf2\x2c\xed\x4d\x91\xef\x43\x15\x40\x67\x6d\xfa\x00\xd5\xe1\x10\x7e\x31\x16\x93\x94\x58\x86\x1b\x2b\x9b\x31\xca\xe4\x84\xe7\x9d\x58\xc5\x33\x05\x1c\x17\x38",
> 39);
>         memcpy((void*)0x20002000,
> "\x02\x00\x33\xe3\x7f\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00",
> 128);
>         syscall(SYS_sendto, fd, 0x20003000ul, 0x27ul,
> 0x69a6e88a31dc2927ul, 0x20002000ul, 0x80ul);
>         return 0;
> }
>
> void *thr1(void *arg)
> {
>         syscall(SYS_read, fd, 0x20005000ul, 0xcbul, 0, 0, 0);
>         return 0;
> }
>
> void *thr2(void *arg)
> {
>         syscall(SYS_close, fd, 0, 0, 0, 0, 0);
>         return 0;
> }
>
> int main()
> {
>         syscall(SYS_mmap, 0x20000000ul, 0x10000ul, 0x3ul, 0x32ul,
> 0xfffffffffffffffful, 0x0ul);
>         fd = syscall(SYS_socket, PF_INET, SOCK_STREAM, IPPROTO_IP);
>         memcpy((void*)0x20000000,
> "\x02\x00\x33\xe3\x7f\x00\x00\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00",
> 128);
>         long r3 = syscall(SYS_bind, fd, 0x20000000ul, 0x80ul, 0, 0, 0);
>         pthread_t th[3];
>         pthread_create(&th[0], 0, thr0, 0);
>         pthread_create(&th[1], 0, thr1, 0);
>         pthread_create(&th[2], 0, thr2, 0);
>         pthread_join(th[0], 0);
>         pthread_join(th[1], 0);
>         pthread_join(th[2], 0);
>         return 0;
> }
>
>
> ------------[ cut here ]------------
> WARNING: CPU: 2 PID: 1991 at net/ipv4/tcp.c:1729 tcp_recvmsg+0x171f/0x2ba0()
> Modules linked in:
> CPU: 2 PID: 1991 Comm: a.out Tainted: G    B   W       4.4.0-rc2+ #51
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>  ffffffff85ac2e60 ffff8800321af8d0 ffffffff826c8be0 0000000000000000
>  ffff8800321af910 ffffffff81233651 ffffffff8464bfbf 0000000000000000
>  0000000000000000 ffff880033545080 ffff88003354589c ffff8800335457f0
> Call Trace:
>  [<ffffffff81233815>] warn_slowpath_null+0x15/0x20 kernel/panic.c:493
>  [<ffffffff8464bfbf>] tcp_recvmsg+0x171f/0x2ba0 net/ipv4/tcp.c:1728
>  [<ffffffff84713328>] inet_recvmsg+0x2a8/0x460 net/ipv4/af_inet.c:764
>  [<     inline     >] sock_recvmsg_nosec net/socket.c:712
>  [<ffffffff842b1d1d>] sock_recvmsg+0x7d/0xa0 net/socket.c:720
>  [<ffffffff842b1f4b>] sock_read_iter+0x20b/0x3b0 net/socket.c:797
>  [<     inline     >] new_sync_read fs/read_write.c:422
>  [<ffffffff81633d5b>] __vfs_read+0x26b/0x490 fs/read_write.c:434
>  [<ffffffff81635edb>] vfs_read+0xdb/0x2d0 fs/read_write.c:454
>  [<     inline     >] SYSC_read fs/read_write.c:569
>  [<ffffffff81638c1c>] SyS_read+0x10c/0x220 fs/read_write.c:562
>  [<ffffffff852a7876>] entry_SYSCALL_64_fastpath+0x16/0x7a
> arch/x86/entry/entry_64.S:185
> ---[ end trace a91322778567c814 ]---
>
>
> I am on commit 6ffeba9607343f15303a399bc402a538800d89d9 (Now 24).
>
> Thank you

I could not see your mail on netdev, only in my private mailbox.

I hope this answer will make it, I removed some of the recipients, as
really netdev is what matters.

Cross SYN were probably never correctly tested with random stuff I guess...

Could you test following fix ?

Thanks.

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a4a0b6b3bcf2..2d656eef7f8e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5683,6 +5683,7 @@ discard:
                }

                tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1;
+               tp->copied_seq = tp->rcv_nxt;
                tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1;

                /* RFC1323: The window in SYN & SYN/ACK segments is
--
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