linux-kernel - [syzbot] [net?] KMSAN: uninit-value in mkiss_receive

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Message-ID: <683785d8.a70a0220.1765ec.017d.GAE@google.com>
Date: Wed, 28 May 2025 14:53:28 -0700
From: syzbot <syzbot+dca31068cff20d2ad44d@...kaller.appspotmail.com>
To: andrew+netdev@...n.ch, davem@...emloft.net, edumazet@...gle.com, 
	kuba@...nel.org, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
	pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [net?] KMSAN: uninit-value in mkiss_receive_buf

Hello,

syzbot found the following issue on:

HEAD commit:    0f8c0258bf04 Merge tag 'mm-hotfixes-stable-2025-05-25-00-5..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=151b0df4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=a423536a47898618
dashboard link: https://syzkaller.appspot.com/bug?extid=dca31068cff20d2ad44d
compiler:       Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/29899159fd0d/disk-0f8c0258.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/5559f4a31e21/vmlinux-0f8c0258.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7fe7bf82ed6b/bzImage-0f8c0258.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+dca31068cff20d2ad44d@...kaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in kiss_unesc drivers/net/hamradio/mkiss.c:303 [inline]
BUG: KMSAN: uninit-value in mkiss_receive_buf+0x5a6/0x23c0 drivers/net/hamradio/mkiss.c:901
 kiss_unesc drivers/net/hamradio/mkiss.c:303 [inline]
 mkiss_receive_buf+0x5a6/0x23c0 drivers/net/hamradio/mkiss.c:901
 tty_ldisc_receive_buf+0x1f4/0x2c0 drivers/tty/tty_buffer.c:391
 tty_port_default_receive_buf+0xd7/0x1a0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:445 [inline]
 flush_to_ldisc+0x44f/0xdb0 drivers/tty/tty_buffer.c:495
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xb9a/0x1d90 kernel/workqueue.c:3319
 worker_thread+0xedf/0x1590 kernel/workqueue.c:3400
 kthread+0xd5c/0xf00 kernel/kthread.c:464
 ret_from_fork+0x71/0x90 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Uninit was stored to memory at:
 mkiss_receive_buf+0x59f/0x23c0 drivers/net/hamradio/mkiss.c:901
 tty_ldisc_receive_buf+0x1f4/0x2c0 drivers/tty/tty_buffer.c:391
 tty_port_default_receive_buf+0xd7/0x1a0 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:445 [inline]
 flush_to_ldisc+0x44f/0xdb0 drivers/tty/tty_buffer.c:495
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xb9a/0x1d90 kernel/workqueue.c:3319
 worker_thread+0xedf/0x1590 kernel/workqueue.c:3400
 kthread+0xd5c/0xf00 kernel/kthread.c:464
 ret_from_fork+0x71/0x90 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4153 [inline]
 slab_alloc_node mm/slub.c:4196 [inline]
 __do_kmalloc_node mm/slub.c:4326 [inline]
 __kmalloc_noprof+0x95f/0x1310 mm/slub.c:4339
 kmalloc_noprof include/linux/slab.h:909 [inline]
 tty_buffer_alloc drivers/tty/tty_buffer.c:180 [inline]
 __tty_buffer_request_room+0x3d4/0x7a0 drivers/tty/tty_buffer.c:273
 __tty_insert_flip_string_flags+0x157/0x6f0 drivers/tty/tty_buffer.c:309
 tty_insert_flip_char include/linux/tty_flip.h:77 [inline]
 uart_insert_char+0x368/0x930 drivers/tty/serial/serial_core.c:3515
 serial8250_read_char+0x1ba/0x670 drivers/tty/serial/8250/8250_port.c:1764
 serial8250_rx_chars drivers/tty/serial/8250/8250_port.c:1781 [inline]
 serial8250_handle_irq+0x930/0x1110 drivers/tty/serial/8250/8250_port.c:1945
 serial8250_default_handle_irq+0x116/0x2b0 drivers/tty/serial/8250/8250_port.c:1970
 serial8250_interrupt+0xc8/0x400 drivers/tty/serial/8250/8250_core.c:86
 __handle_irq_event_percpu+0x11c/0xbf0 kernel/irq/handle.c:158
 handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
 handle_irq_event+0xe0/0x2a0 kernel/irq/handle.c:210
 handle_edge_irq+0x450/0xfd0 kernel/irq/chip.c:831
 generic_handle_irq_desc include/linux/irqdesc.h:173 [inline]
 handle_irq arch/x86/kernel/irq.c:254 [inline]
 call_irq_handler arch/x86/kernel/irq.c:266 [inline]
 __common_interrupt+0xa2/0x220 arch/x86/kernel/irq.c:292
 common_interrupt+0x94/0xb0 arch/x86/kernel/irq.c:285
 asm_common_interrupt+0x2b/0x40 arch/x86/include/asm/idtentry.h:693

CPU: 0 UID: 0 PID: 4519 Comm: kworker/u8:20 Not tainted 6.15.0-rc7-syzkaller-00175-g0f8c0258bf04 #0 PREEMPT(undef) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: events_unbound flush_to_ldisc
=====================================================


---
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