[syzbot] [serial?] KMSAN: uninit-value in gsmld_receive_buf

[syzbot <syzbot+2f64914d6a3a8ce91bdd@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    e88c4cfcb7b8 Merge tag 'for-6.9-rc5-tag' of git://git.kern..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1664a5e8980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=776c05250f36d55c
dashboard link: https://syzkaller.appspot.com/bug?extid=2f64914d6a3a8ce91bdd
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/76771e00ba79/disk-e88c4cfc.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c957ed943a4f/vmlinux-e88c4cfc.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e719306ed8e3/bzImage-e88c4cfc.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2f64914d6a3a8ce91bdd@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in gsmld_receive_buf+0x5dc/0x640 drivers/tty/n_gsm.c:3555
 gsmld_receive_buf+0x5dc/0x640 drivers/tty/n_gsm.c:3555
 tty_ldisc_receive_buf+0x202/0x290 drivers/tty/tty_buffer.c:391
 tty_port_default_receive_buf+0xdf/0x190 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:445 [inline]
 flush_to_ldisc+0x473/0xdb0 drivers/tty/tty_buffer.c:495
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0xa81/0x1bd0 kernel/workqueue.c:3335
 worker_thread+0xea5/0x1560 kernel/workqueue.c:3416
 kthread+0x3e2/0x540 kernel/kthread.c:388
 ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:3804 [inline]
 slab_alloc_node mm/slub.c:3845 [inline]
 __do_kmalloc_node mm/slub.c:3965 [inline]
 __kmalloc+0x6e4/0x1000 mm/slub.c:3979
 kmalloc include/linux/slab.h:632 [inline]
 tty_buffer_alloc drivers/tty/tty_buffer.c:180 [inline]
 __tty_buffer_request_room+0x36e/0x6d0 drivers/tty/tty_buffer.c:273
 __tty_insert_flip_string_flags+0x140/0x570 drivers/tty/tty_buffer.c:309
 tty_insert_flip_char include/linux/tty_flip.h:77 [inline]
 uart_insert_char+0x39e/0xa10 drivers/tty/serial/serial_core.c:3558
 serial8250_read_char+0x1a7/0x5d0 drivers/tty/serial/8250/8250_port.c:1750
 serial8250_rx_chars drivers/tty/serial/8250/8250_port.c:1767 [inline]
 serial8250_handle_irq+0x77a/0xb80 drivers/tty/serial/8250/8250_port.c:1927
 serial8250_default_handle_irq+0x120/0x2b0 drivers/tty/serial/8250/8250_port.c:1952
 serial8250_interrupt+0xc5/0x360 drivers/tty/serial/8250/8250_core.c:127
 __handle_irq_event_percpu+0x118/0xca0 kernel/irq/handle.c:158
 handle_irq_event_percpu kernel/irq/handle.c:193 [inline]
 handle_irq_event+0xef/0x2c0 kernel/irq/handle.c:210
 handle_edge_irq+0x340/0xfb0 kernel/irq/chip.c:831
 generic_handle_irq_desc include/linux/irqdesc.h:161 [inline]
 handle_irq arch/x86/kernel/irq.c:238 [inline]
 __common_interrupt+0x97/0x1f0 arch/x86/kernel/irq.c:257
 common_interrupt+0x49/0xa0 arch/x86/kernel/irq.c:247
 asm_common_interrupt+0x2b/0x40 arch/x86/include/asm/idtentry.h:693

CPU: 1 PID: 14392 Comm: kworker/u8:1 Not tainted 6.9.0-rc5-syzkaller-00042-ge88c4cfcb7b8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Workqueue: events_unbound flush_to_ldisc
=====================================================


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