[syzbot] [serial?] KMSAN: kernel-infoleak in tty_read

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 6a0e38264012 Merge tag 'for-6.11-rc2-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1489f27d980000
kernel config: https://syzkaller.appspot.com/x/.config?x=305509ad8eb5f9b8
dashboard link: https://syzkaller.appspot.com/bug?extid=aa7ddf2352c316bb08d0
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/82fdd1f77a94/disk-6a0e3826.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cc02539b71e6/vmlinux-6a0e3826.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5f2caa5e7e58/bzImage-6a0e3826.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+aa7ddf...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:114 [inline]
BUG: KMSAN: kernel-infoleak in copy_to_user_iter lib/iov_iter.c:24 [inline]
BUG: KMSAN: kernel-infoleak in iterate_iovec include/linux/iov_iter.h:51 [inline]
BUG: KMSAN: kernel-infoleak in iterate_and_advance2 include/linux/iov_iter.h:247 [inline]
BUG: KMSAN: kernel-infoleak in iterate_and_advance include/linux/iov_iter.h:271 [inline]
BUG: KMSAN: kernel-infoleak in _copy_to_iter+0x7c7/0x24a0 lib/iov_iter.c:185
instrument_copy_to_user include/linux/instrumented.h:114 [inline]
copy_to_user_iter lib/iov_iter.c:24 [inline]
iterate_iovec include/linux/iov_iter.h:51 [inline]
iterate_and_advance2 include/linux/iov_iter.h:247 [inline]
iterate_and_advance include/linux/iov_iter.h:271 [inline]
_copy_to_iter+0x7c7/0x24a0 lib/iov_iter.c:185
copy_to_iter include/linux/uio.h:196 [inline]
iterate_tty_read drivers/tty/tty_io.c:882 [inline]
tty_read+0x42c/0xe10 drivers/tty/tty_io.c:937
do_iter_readv_writev+0x8a1/0xa40
vfs_readv+0x36c/0xef0 fs/read_write.c:932
do_readv+0x251/0x5c0 fs/read_write.c:994
__do_sys_readv fs/read_write.c:1085 [inline]
__se_sys_readv fs/read_write.c:1082 [inline]
__x64_sys_readv+0x98/0xe0 fs/read_write.c:1082
x64_sys_call+0x3889/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:20
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was stored to memory at:
copy_from_read_buf drivers/tty/n_tty.c:1978 [inline]
n_tty_read+0x2196/0x3260 drivers/tty/n_tty.c:2304
iterate_tty_read drivers/tty/tty_io.c:862 [inline]
tty_read+0x327/0xe10 drivers/tty/tty_io.c:937
do_iter_readv_writev+0x8a1/0xa40
vfs_readv+0x36c/0xef0 fs/read_write.c:932
do_readv+0x251/0x5c0 fs/read_write.c:994
__do_sys_readv fs/read_write.c:1085 [inline]
__se_sys_readv fs/read_write.c:1082 [inline]
__x64_sys_readv+0x98/0xe0 fs/read_write.c:1082
x64_sys_call+0x3889/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:20
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was stored to memory at:
n_tty_receive_buf_real_raw drivers/tty/n_tty.c:1532 [inline]
__receive_buf drivers/tty/n_tty.c:1618 [inline]
n_tty_receive_buf_common+0xe6e/0x2490 drivers/tty/n_tty.c:1739
n_tty_receive_buf2+0x4c/0x60 drivers/tty/n_tty.c:1785
tty_ldisc_receive_buf+0xd0/0x290 drivers/tty/tty_buffer.c:387
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_string_fixed_flag include/linux/tty_flip.h:35 [inline]
tty_insert_flip_string include/linux/tty_flip.h:83 [inline]
puts_queue drivers/tty/vt/keyboard.c:333 [inline]
k_fn+0x154/0x1e0 drivers/tty/vt/keyboard.c:776
k_pad+0x461/0xc40
kbd_keycode drivers/tty/vt/keyboard.c:1522 [inline]
kbd_event+0x5e2c/0x6010 drivers/tty/vt/keyboard.c:1541
input_handler_events_default+0x128/0x1f0 drivers/input/input.c:2552
input_pass_values+0x216/0x990 drivers/input/input.c:126
input_event_dispose+0x552/0x6e0 drivers/input/input.c:352
input_handle_event+0xf3c/0x1430 drivers/input/input.c:369
input_event+0xe2/0x120 drivers/input/input.c:398
hidinput_hid_event+0x256d/0x2960 drivers/hid/hid-input.c:1746
hid_process_event+0x766/0x930 drivers/hid/hid-core.c:1540
hid_input_array_field+0x768/0x850 drivers/hid/hid-core.c:1652
hid_process_report drivers/hid/hid-core.c:1694 [inline]
hid_report_raw_event+0x1d22/0x2820 drivers/hid/hid-core.c:2015
__hid_input_report drivers/hid/hid-core.c:2085 [inline]
hid_input_report+0x5a2/0x610 drivers/hid/hid-core.c:2107
hid_irq_in+0x737/0xd00 drivers/hid/usbhid/hid-core.c:285
__usb_hcd_giveback_urb+0x572/0x840 drivers/usb/core/hcd.c:1650
usb_hcd_giveback_urb+0x157/0x720 drivers/usb/core/hcd.c:1734
dummy_timer+0xd3f/0x6aa0 drivers/usb/gadget/udc/dummy_hcd.c:1987
__run_hrtimer kernel/time/hrtimer.c:1689 [inline]
__hrtimer_run_queues+0x564/0xe40 kernel/time/hrtimer.c:1753
hrtimer_interrupt+0x3ab/0x1490 kernel/time/hrtimer.c:1815
local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1032 [inline]
__sysvec_apic_timer_interrupt+0xa6/0x3a0 arch/x86/kernel/apic/apic.c:1049
instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1043 [inline]
sysvec_apic_timer_interrupt+0x7e/0x90 arch/x86/kernel/apic/apic.c:1043
asm_sysvec_apic_timer_interrupt+0x1f/0x30 arch/x86/include/asm/idtentry.h:702

Bytes 8-11 of 20 are uninitialized
Memory access of size 20 starts at ffff88813f5ebb40
Data copied to user address 0000000020000280

CPU: 1 UID: 0 PID: 6504 Comm: syz.3.387 Not tainted 6.11.0-rc2-syzkaller-00027-g6a0e38264012 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
=====================================================


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