[syzbot] WARNING: suspicious RCU usage in tcp_bpf_update_proto

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 514e1150 net: x25: Queue received packets in the drivers i..
git tree: net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=112a8831d00000
kernel config: https://syzkaller.appspot.com/x/.config?x=7eff0f22b8563a5f
dashboard link: https://syzkaller.appspot.com/bug?extid=320a3bc8d80f478c37e4
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1532d711d00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15f44c5ed00000

The issue was bisected to:

commit 4dfe6bd94959222e18d512bdf15f6bf9edb9c27c
Author: Rustam Kovhaev <rkov...@gmail.com>
Date: Wed Feb 24 20:00:30 2021 +0000

ntfs: check for valid standard information attribute

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=16207a81d00000
final oops: https://syzkaller.appspot.com/x/report.txt?x=15207a81d00000
console output: https://syzkaller.appspot.com/x/log.txt?x=11207a81d00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+320a3b...@syzkaller.appspotmail.com
Fixes: 4dfe6bd94959 ("ntfs: check for valid standard information attribute")

=============================
WARNING: suspicious RCU usage
5.12.0-rc4-syzkaller #0 Not tainted
-----------------------------
include/linux/skmsg.h:286 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz-executor383/8454:
#0: ffff888013a99b48 (clock-AF_INET){++..}-{2:2}, at: sk_psock_drop+0x2c/0x460 net/core/skmsg.c:788

stack backtrace:
CPU: 1 PID: 8454 Comm: syz-executor383 Not tainted 5.12.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:79 [inline]
dump_stack+0x141/0x1d7 lib/dump_stack.c:120
sk_psock include/linux/skmsg.h:286 [inline]
tcp_bpf_update_proto+0x530/0x5f0 net/ipv4/tcp_bpf.c:504
sk_psock_restore_proto include/linux/skmsg.h:408 [inline]
sk_psock_drop+0xdf/0x460 net/core/skmsg.c:789
sk_psock_put include/linux/skmsg.h:446 [inline]
tcp_bpf_recvmsg+0x42d/0x480 net/ipv4/tcp_bpf.c:208
inet_recvmsg+0x11b/0x5d0 net/ipv4/af_inet.c:852
sock_recvmsg_nosec net/socket.c:888 [inline]
sock_recvmsg net/socket.c:906 [inline]
sock_recvmsg net/socket.c:902 [inline]
____sys_recvmsg+0x2c4/0x600 net/socket.c:2569
___sys_recvmsg+0x127/0x200 net/socket.c:2611
do_recvmmsg+0x24d/0x6d0 net/socket.c:2705
__sys_recvmmsg net/socket.c:2784 [inline]
__do_sys_recvmmsg net/socket.c:2807 [inline]
__se_sys_recvmmsg net/socket.c:2800 [inline]
__x64_sys_recvmmsg+0x20b/0x260 net/socket.c:2800
do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x4468e9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 a1 15 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f010b0cc318 EFLAGS: 00000246 ORIG_RAX: 000000000000012b
RAX: ffffffffffffffda RBX: 00000000004cb4e8 RCX: 00000000004468e9
RDX: 0000000000000422 RSI: 0000000020000540 RDI: 0000000000000004
RBP: 00000000004cb4e0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000049b270
R13: 00007ffe3829a5bf R14: 00007f010b0cc400 R15: 0000000000022000


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection
syzbot can test patches for this issue, for details see:
https://goo.gl/tpsmEJ#testing-patches

[Cong Wang]

On Tue, Apr 6, 2021 at 2:44 AM syzbot
<syzbot+320a3b...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 514e1150 net: x25: Queue received packets in the drivers i..
> git tree: net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=112a8831d00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=7eff0f22b8563a5f
> dashboard link: https://syzkaller.appspot.com/bug?extid=320a3bc8d80f478c37e4
> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1532d711d00000
> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=15f44c5ed00000
>
> The issue was bisected to:
>
> commit 4dfe6bd94959222e18d512bdf15f6bf9edb9c27c
> Author: Rustam Kovhaev <rkov...@gmail.com>
> Date: Wed Feb 24 20:00:30 2021 +0000
>
> ntfs: check for valid standard information attribute

This is caused by one of my sockmap patches.

Oddly, I have all relevant Kconfig enabled but never see this
warning when running selftests for hours....

Anyway, let me see how this should be fixed.

Thanks!

[John Fastabend]

The bisection is bogus, but we will get a fix for this ASAP. The real commit
is,

commit 8a59f9d1e3d4340659fdfee8879dc09a6f2546e1
Author: Cong Wang <cong...@bytedance.com>
Date: Tue Mar 30 19:32:31 2021 -0700

sock: Introduce sk->sk_prot->psock_update_sk_prot()

Thanks,
John

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+320a3b...@syzkaller.appspotmail.com

Tested on:

commit: 52b062f9 skmsg: pass psock pointer to ->psock_update_sk_pr..
git tree: https://github.com/congwang/linux.git bpf-next
kernel config: https://syzkaller.appspot.com/x/.config?x=3465aa821afbdd7f
dashboard link: https://syzkaller.appspot.com/bug?extid=320a3bc8d80f478c37e4
compiler:

Note: testing is done by a robot and is best-effort only.