Re: general protection fault in tls_sk_proto_close (2)

[Jakub Kicinski]

On Tue, 27 Aug 2019 23:38:07 -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    a55aa89a Linux 5.3-rc6
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16c26ebc600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2a6a2b9826fdadf9
> dashboard link: https://syzkaller.appspot.com/bug?extid=7a6ee4d0078eac6bf782
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1112a4de600000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+7a6ee4d0078eac6bf782@xxxxxxxxxxxxxxxxxxxxxxxxx

Hi John!

This is a loop where TLS calls it's own close function recursively.
It seems we must have gotten BPF installed on top of TLS, and then 
it handed TLS TLS'es own sk_proto via tcp_update_ulp().

Can BPF on top of TLS be prevented somehow?

Quick fix should probably be something like:

diff --git a/net/tls/tls_main.c b/net/tls/tls_main.c
index 43252a801c3f..3f4962756fa4 100644
--- a/net/tls/tls_main.c
+++ b/net/tls/tls_main.c
@@ -816,6 +816,9 @@ static void tls_update(struct sock *sk, struct proto *p)
 
        ctx = tls_get_ctx(sk);
        if (likely(ctx)) {
+               if (p->setsockopt == tls_setsockopt)
+                       return;
+
                ctx->sk_proto_close = p->close;
                ctx->sk_proto = p;
        } else {

> kasan: CONFIG_KASAN_INLINE enabled
> kasan: GPF could be caused by NULL-ptr deref or user memory access
> general protection fault: 0000 [#1] PREEMPT SMP KASAN
> CPU: 1 PID: 10290 Comm: syz-executor.0 Not tainted 5.3.0-rc6 #120
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
> Google 01/01/2011
> RIP: 0010:tls_sk_proto_close+0xe5/0x990 net/tls/tls_main.c:298
> Code: 0f 85 3f 08 00 00 49 8b 84 24 c0 02 00 00 4d 8d 75 14 4c 89 f2 48 c1  
> ea 03 48 89 85 50 ff ff ff 48 b8 00 00 00 00 00 fc ff df <0f> b6 04 02 4c  
> 89 f2 83 e2 07 38 d0 7f 08 84 c0 0f 85 2e 06 00 00
> RSP: 0018:ffff88809b23fb90 EFLAGS: 00010203
> RAX: dffffc0000000000 RBX: dffffc0000000000 RCX: ffffffff862cb8db
> RDX: 0000000000000002 RSI: ffffffff862cb639 RDI: ffff8880a155ef00
> RBP: ffff88809b23fc48 R08: ffff888094344640 R09: ffffed10142abd9a
> R10: ffffed10142abd99 R11: ffff8880a155eccb R12: ffff8880a155ec40
> R13: 0000000000000000 R14: 0000000000000014 R15: 0000000000000001
> FS:  00005555556a8940(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f353458e000 CR3: 00000000a9174000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>   tls_sk_proto_close+0x35b/0x990 net/tls/tls_main.c:321
>   tcp_bpf_close+0x17c/0x390 net/ipv4/tcp_bpf.c:582
>   inet_release+0xed/0x200 net/ipv4/af_inet.c:427
>   inet6_release+0x53/0x80 net/ipv6/af_inet6.c:470
>   __sock_release+0xce/0x280 net/socket.c:590
>   sock_close+0x1e/0x30 net/socket.c:1268
>   __fput+0x2ff/0x890 fs/file_table.c:280
>   ____fput+0x16/0x20 fs/file_table.c:313
>   task_work_run+0x145/0x1c0 kernel/task_work.c:113
>   tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>   exit_to_usermode_loop+0x316/0x380 arch/x86/entry/common.c:163
>   prepare_exit_to_usermode arch/x86/entry/common.c:194 [inline]
>   syscall_return_slowpath arch/x86/entry/common.c:274 [inline]
>   do_syscall_64+0x5a9/0x6a0 arch/x86/entry/common.c:299
>   entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x413540
> Code: 01 f0 ff ff 0f 83 30 1b 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f  
> 44 00 00 83 3d 4d 2d 66 00 00 75 14 b8 03 00 00 00 0f 05 <48> 3d 01 f0 ff  
> ff 0f 83 04 1b 00 00 c3 48 83 ec 08 e8 0a fc ff ff
> RSP: 002b:00007fff5d481778 EFLAGS: 00000246 ORIG_RAX: 0000000000000003
> RAX: 0000000000000000 RBX: 0000000000000006 RCX: 0000000000413540
> RDX: 0000001b2e520000 RSI: 0000000000000000 RDI: 0000000000000005
> RBP: 0000000000000001 R08: 0000000000000000 R09: ffffffffffffffff
> R10: 0000000000000000 R11: 0000000000000246 R12: 000000000075bf20
> R13: 0000000000000003 R14: 0000000000761220 R15: ffffffffffffffff
> Modules linked in:
> ---[ end trace bdfd4385a0f1f76d ]---
> RIP: 0010:tls_sk_proto_close+0xe5/0x990 net/tls/tls_main.c:298
> Code: 0f 85 3f 08 00 00 49 8b 84 24 c0 02 00 00 4d 8d 75 14 4c 89 f2 48 c1  
> ea 03 48 89 85 50 ff ff ff 48 b8 00 00 00 00 00 fc ff df <0f> b6 04 02 4c  
> 89 f2 83 e2 07 38 d0 7f 08 84 c0 0f 85 2e 06 00 00
> RSP: 0018:ffff88809b23fb90 EFLAGS: 00010203
> RAX: dffffc0000000000 RBX: dffffc0000000000 RCX: ffffffff862cb8db
> RDX: 0000000000000002 RSI: ffffffff862cb639 RDI: ffff8880a155ef00
> RBP: ffff88809b23fc48 R08: ffff888094344640 R09: ffffed10142abd9a
> R10: ffffed10142abd99 R11: ffff8880a155eccb R12: ffff8880a155ec40
> R13: 0000000000000000 R14: 0000000000000014 R15: 0000000000000001
> FS:  00005555556a8940(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f353458e000 CR3: 00000000a9174000 CR4: 00000000001406e0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> 
> 
> ---
> This bug 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 syzkaller@xxxxxxxxxxxxxxxxx
> 
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches