On Wed, Aug 21, 2024 at 03:55:33PM +0100, Simon Horman wrote:
> On Tue, Aug 20, 2024 at 08:07:44PM -0700, Cong Wang wrote:
> > From: Cong Wang <cong.wang@xxxxxxxxxxxxx>
> >
> > When we cork messages in psock->cork, the last message triggers the
> > flushing will result in sending a sk_msg larger than the current
> > message size. In this case, in tcp_bpf_send_verdict(), 'copied' becomes
> > negative at least in the following case:
> >
> > 468 case __SK_DROP:
> > 469 default:
> > 470 sk_msg_free_partial(sk, msg, tosend);
> > 471 sk_msg_apply_bytes(psock, tosend);
> > 472 *copied -= (tosend + delta); // <==== HERE
> > 473 return -EACCES;
> >
> > Therefore, it could lead to the following BUG with a proper value of
> > 'copied' (thanks to syzbot). We should not use negative 'copied' as a
> > return value here.
> >
> > ------------[ cut here ]------------
> > kernel BUG at net/socket.c:733!
> > Internal error: Oops - BUG: 00000000f2000800 [#1] PREEMPT SMP
> > Modules linked in:
> > CPU: 0 UID: 0 PID: 3265 Comm: syz-executor510 Not tainted 6.11.0-rc3-syzkaller-00060-gd07b43284ab3 #0
> > Hardware name: linux,dummy-virt (DT)
> > pstate: 61400009 (nZCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--)
> > pc : sock_sendmsg_nosec net/socket.c:733 [inline]
> > pc : sock_sendmsg_nosec net/socket.c:728 [inline]
> > pc : __sock_sendmsg+0x5c/0x60 net/socket.c:745
> > lr : sock_sendmsg_nosec net/socket.c:730 [inline]
> > lr : __sock_sendmsg+0x54/0x60 net/socket.c:745
> > sp : ffff800088ea3b30
> > x29: ffff800088ea3b30 x28: fbf00000062bc900 x27: 0000000000000000
> > x26: ffff800088ea3bc0 x25: ffff800088ea3bc0 x24: 0000000000000000
> > x23: f9f00000048dc000 x22: 0000000000000000 x21: ffff800088ea3d90
> > x20: f9f00000048dc000 x19: ffff800088ea3d90 x18: 0000000000000001
> > x17: 0000000000000000 x16: 0000000000000000 x15: 000000002002ffaf
> > x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
> > x11: 0000000000000000 x10: ffff8000815849c0 x9 : ffff8000815b49c0
> > x8 : 0000000000000000 x7 : 000000000000003f x6 : 0000000000000000
> > x5 : 00000000000007e0 x4 : fff07ffffd239000 x3 : fbf00000062bc900
> > x2 : 0000000000000000 x1 : 0000000000000000 x0 : 00000000fffffdef
> > Call trace:
> > sock_sendmsg_nosec net/socket.c:733 [inline]
> > __sock_sendmsg+0x5c/0x60 net/socket.c:745
> > ____sys_sendmsg+0x274/0x2ac net/socket.c:2597
> > ___sys_sendmsg+0xac/0x100 net/socket.c:2651
> > __sys_sendmsg+0x84/0xe0 net/socket.c:2680
> > __do_sys_sendmsg net/socket.c:2689 [inline]
> > __se_sys_sendmsg net/socket.c:2687 [inline]
> > __arm64_sys_sendmsg+0x24/0x30 net/socket.c:2687
> > __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
> > invoke_syscall+0x48/0x110 arch/arm64/kernel/syscall.c:49
> > el0_svc_common.constprop.0+0x40/0xe0 arch/arm64/kernel/syscall.c:132
> > do_el0_svc+0x1c/0x28 arch/arm64/kernel/syscall.c:151
> > el0_svc+0x34/0xec arch/arm64/kernel/entry-common.c:712
> > el0t_64_sync_handler+0x100/0x12c arch/arm64/kernel/entry-common.c:730
> > el0t_64_sync+0x19c/0x1a0 arch/arm64/kernel/entry.S:598
> > Code: f9404463 d63f0060 3108441f 54fffe81 (d4210000)
> > ---[ end trace 0000000000000000 ]---
> >
> > Fixes: 4f738adba30a ("bpf: create tcp_bpf_ulp allowing BPF to monitor socket TX/RX data")
> > Reported-by: syzbot+58c03971700330ce14d8@xxxxxxxxxxxxxxxxxxxxxxxxx
> > Cc: John Fastabend <john.fastabend@xxxxxxxxx>
> > Cc: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx>
> > Signed-off-by: Cong Wang <cong.wang@xxxxxxxxxxxxx>
> > ---
> > net/ipv4/tcp_bpf.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/net/ipv4/tcp_bpf.c b/net/ipv4/tcp_bpf.c
> > index 53b0d62fd2c2..fe6178715ba0 100644
> > --- a/net/ipv4/tcp_bpf.c
> > +++ b/net/ipv4/tcp_bpf.c
> > @@ -577,7 +577,7 @@ static int tcp_bpf_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
> > err = sk_stream_error(sk, msg->msg_flags, err);
> > release_sock(sk);
> > sk_psock_put(sk, psock);
> > - return copied ? copied : err;
> > + return copied > 0 ? copied : err;
>
> Does it make more sense to make the condition err:
> is err 0 iif everything is ok? (completely untested!)
Mind to elaborate?
