linux-kernel - Re: [syzbot] [serial?] possible deadlock in uart

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Date: Thu, 23 May 2024 04:51:02 -0700
From: syzbot <syzbot+57cc2f20a84cb4346354@...kaller.appspotmail.com>
To: hdanton@...a.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [serial?] possible deadlock in uart_write (2)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
WARNING in uart_write

sp0: Synchronizing with TNC
------------[ cut here ]------------
WARNING: CPU: 2 PID: 5387 at drivers/tty/serial/serial_core.c:627 uart_write+0x2c3/0x3e0 drivers/tty/serial/serial_core.c:627
Modules linked in:
CPU: 2 PID: 5387 Comm: syz-executor Not tainted 6.9.0-syzkaller-11924-gde7e71ef8bed-dirty #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:uart_write+0x2c3/0x3e0 drivers/tty/serial/serial_core.c:627
Code: 00 00 48 8d 98 9c 03 00 00 48 89 df e8 e6 c9 ec fc f0 ff 0b 0f 94 c3 31 ff 89 de e8 77 dc 90 fc 84 db 75 72 e8 ce e1 90 fc 90 <0f> 0b 90 31 ed e9 23 ff ff ff e8 be e1 90 fc 4c 89 ea 48 b8 00 00
RSP: 0018:ffffc900036a7bd8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff88801f5a8f00 RCX: ffffffff84fd0ab9
RDX: ffff888021d00000 RSI: ffffffff84fd0ac2 RDI: 0000000000000001
RBP: ffffffff94de7028 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000002 R12: ffffffff94de6f20
R13: 0000000000000001 R14: ffff88801231cf01 R15: 0000000000000293
FS:  00007f2677c386c0(0000) GS:ffff88806b200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000555575a07788 CR3: 0000000020ab6000 CR4: 0000000000350ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 tnc_init drivers/net/hamradio/6pack.c:531 [inline]
 sixpack_open+0x93b/0xb30 drivers/net/hamradio/6pack.c:628
 tty_ldisc_open+0x9c/0x120 drivers/tty/tty_ldisc.c:432
 tty_set_ldisc+0x318/0x720 drivers/tty/tty_ldisc.c:563
 tiocsetd drivers/tty/tty_io.c:2439 [inline]
 tty_ioctl+0xbdc/0x15f0 drivers/tty/tty_io.c:2739
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:907 [inline]
 __se_sys_ioctl fs/ioctl.c:893 [inline]
 __x64_sys_ioctl+0x193/0x220 fs/ioctl.c:893
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2676e7cee9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f2677c380c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f2676fabf80 RCX: 00007f2676e7cee9
RDX: 0000000020000080 RSI: 0000000000005423 RDI: 0000000000000003
RBP: 00007f2676ec949e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f2676fabf80 R15: 00007ffeb4e97fa8
 </TASK>


Tested on:

commit:         de7e71ef mm: simplify and improve print_vma_addr() out..
git tree:       https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=16d0ae1a980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=45d62832ec0fc911
dashboard link: https://syzkaller.appspot.com/bug?extid=57cc2f20a84cb4346354
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=11a3a51a980000