UBSAN: array-index-out-of-bounds in decode_data

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    9791581c Merge tag 'for-5.11-rc4-tag' of git://git.kernel...
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11970b20d00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=39701af622f054a9
dashboard link: https://syzkaller.appspot.com/bug?extid=70ba6cae2f44c82dcb76
compiler:       gcc (GCC) 10.1.0-syz 20200507

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+70ba6cae2f44c82dcb76@xxxxxxxxxxxxxxxxxxxxxxxxx

UBSAN: array-index-out-of-bounds in drivers/net/hamradio/6pack.c:845:16
index 400 is out of range for type 'unsigned char [400]'
CPU: 0 PID: 24 Comm: kworker/u4:1 Not tainted 5.11.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 ubsan_epilogue+0xb/0x5a lib/ubsan.c:148
 __ubsan_handle_out_of_bounds.cold+0x62/0x6c lib/ubsan.c:356
 decode_data.part.0+0x2c8/0x2e0 drivers/net/hamradio/6pack.c:845
 decode_data drivers/net/hamradio/6pack.c:965 [inline]
 sixpack_decode drivers/net/hamradio/6pack.c:968 [inline]
 sixpack_receive_buf drivers/net/hamradio/6pack.c:458 [inline]
 sixpack_receive_buf+0xd8c/0x1320 drivers/net/hamradio/6pack.c:435
 tty_ldisc_receive_buf+0x14a/0x190 drivers/tty/tty_buffer.c:465
 tty_port_default_receive_buf+0x6e/0xa0 drivers/tty/tty_port.c:38
 receive_buf drivers/tty/tty_buffer.c:481 [inline]
 flush_to_ldisc+0x20d/0x380 drivers/tty/tty_buffer.c:533
 process_one_work+0x98d/0x15f0 kernel/workqueue.c:2275
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
================================================================================
Kernel panic - not syncing: panic_on_warn set ...
CPU: 0 PID: 24 Comm: kworker/u4:1 Not tainted 5.11.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 __dump_stack lib/dump_stack.c:79 [inline]
 dump_stack+0x107/0x163 lib/dump_stack.c:120
 panic+0x306/0x73d kernel/panic.c:231
 ubsan_epilogue+0x54/0x5a lib/ubsan.c:162
 __ubsan_handle_out_of_bounds.cold+0x62/0x6c lib/ubsan.c:356
 decode_data.part.0+0x2c8/0x2e0 drivers/net/hamradio/6pack.c:845
 decode_data drivers/net/hamradio/6pack.c:965 [inline]
 sixpack_decode drivers/net/hamradio/6pack.c:968 [inline]
 sixpack_receive_buf drivers/net/hamradio/6pack.c:458 [inline]
 sixpack_receive_buf+0xd8c/0x1320 drivers/net/hamradio/6pack.c:435
 tty_ldisc_receive_buf+0x14a/0x190 drivers/tty/tty_buffer.c:465
 tty_port_default_receive_buf+0x6e/0xa0 drivers/tty/tty_port.c:38
 receive_buf drivers/tty/tty_buffer.c:481 [inline]
 flush_to_ldisc+0x20d/0x380 drivers/tty/tty_buffer.c:533
 process_one_work+0x98d/0x15f0 kernel/workqueue.c:2275
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296
Kernel Offset: disabled
Rebooting in 86400 seconds..


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