[syzbot] [ppp?] KMSAN: uninit-value in ppp_sync_receive (2)

Hello,

syzbot found the following issue on:

HEAD commit:    defaf1a2113a Merge tag 'scsi-fixes' of git://git.kernel.or..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1034ded9980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9d6059ad10dde6fd
dashboard link: https://syzkaller.appspot.com/bug?extid=d73ee3b9fbad2067c916
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/d4b583db7f7f/disk-defaf1a2.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a61e18e13b2d/vmlinux-defaf1a2.xz
kernel image: https://storage.googleapis.com/syzbot-assets/386b01bc4565/bzImage-defaf1a2.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

=====================================================
BUG: KMSAN: uninit-value in ppp_sync_input drivers/net/ppp/ppp_synctty.c:679 [inline]
BUG: KMSAN: uninit-value in ppp_sync_receive+0x56a/0xf10 drivers/net/ppp/ppp_synctty.c:334
 ppp_sync_input drivers/net/ppp/ppp_synctty.c:679 [inline]
 ppp_sync_receive+0x56a/0xf10 drivers/net/ppp/ppp_synctty.c:334
 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:3231 [inline]
 process_scheduled_works+0xae0/0x1c40 kernel/workqueue.c:3312
 worker_thread+0xea5/0x1520 kernel/workqueue.c:3390
 kthread+0x3dd/0x540 kernel/kthread.c:389
 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:3994 [inline]
 slab_alloc_node mm/slub.c:4037 [inline]
 __do_kmalloc_node mm/slub.c:4157 [inline]
 __kmalloc_noprof+0x661/0xf30 mm/slub.c:4170
 kmalloc_noprof include/linux/slab.h:685 [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:3560
 serial8250_read_char+0x1a7/0x5d0 drivers/tty/serial/8250/8250_port.c:1743
 serial8250_rx_chars drivers/tty/serial/8250/8250_port.c:1760 [inline]
 serial8250_handle_irq+0x77a/0xb80 drivers/tty/serial/8250/8250_port.c:1924
 serial8250_default_handle_irq+0x120/0x2b0 drivers/tty/serial/8250/8250_port.c:1949
 serial8250_interrupt+0xc5/0x360 drivers/tty/serial/8250/8250_core.c:86
 __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:173 [inline]
 handle_irq arch/x86/kernel/irq.c:247 [inline]
 call_irq_handler arch/x86/kernel/irq.c:259 [inline]
 __common_interrupt+0x97/0x1f0 arch/x86/kernel/irq.c:285
 common_interrupt+0x8f/0xa0 arch/x86/kernel/irq.c:278
 asm_common_interrupt+0x2b/0x40 arch/x86/include/asm/idtentry.h:693

CPU: 1 UID: 0 PID: 3154 Comm: kworker/u8:16 Not tainted 6.11.0-rc1-syzkaller-00293-gdefaf1a2113a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Workqueue: events_unbound flush_to_ldisc
=====================================================


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