syzbot has found a reproducer for the following crash on:
HEAD commit: 28f0ca98eadf kmsan: don't instrument do_syscall_64() and _.. git tree: https://github.com/google/kmsan.git/master console output: https://syzkaller.appspot.com/x/log.txt?x=10556c92400000 kernel config: https://syzkaller.appspot.com/x/.config?x=3431f03869413153 dashboard link: https://syzkaller.appspot.com/bug?extid=194dffdb8b22fc5d207a compiler: clang version 8.0.0 (trunk 339414) syz repro: https://syzkaller.appspot.com/x/repro.syz?x=123a520a400000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16068dc1400000
IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+194dffdb8b22fc5d207a@syzkaller.appspotmail.com
================================================================== BUG: KMSAN: uninit-value in snd_midi_event_encode_byte+0x569/0xff0 sound/core/seq/seq_midi_event.c:195 CPU: 1 PID: 1659 Comm: kworker/1:1H Not tainted 4.19.0-rc1+ #40 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events_highpri snd_vmidi_output_work Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x14b/0x190 lib/dump_stack.c:113 kmsan_report+0x183/0x2b0 mm/kmsan/kmsan.c:956 __msan_warning+0x70/0xc0 mm/kmsan/kmsan_instr.c:645 snd_midi_event_encode_byte+0x569/0xff0 sound/core/seq/seq_midi_event.c:195 snd_vmidi_output_work+0x34e/0x5b0 sound/core/seq/seq_virmidi.c:161 process_one_work+0x1605/0x1f40 kernel/workqueue.c:2153 worker_thread+0x11a2/0x2590 kernel/workqueue.c:2296 kthread+0x465/0x4a0 kernel/kthread.c:247 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:416
Uninit was stored to memory at: kmsan_save_stack_with_flags mm/kmsan/kmsan.c:256 [inline] kmsan_save_stack mm/kmsan/kmsan.c:271 [inline] kmsan_internal_chain_origin+0x128/0x210 mm/kmsan/kmsan.c:573 __msan_chain_origin+0x69/0xc0 mm/kmsan/kmsan_instr.c:482 __snd_rawmidi_transmit_peek sound/core/rawmidi.c:1103 [inline] snd_rawmidi_transmit+0xa75/0xbf0 sound/core/rawmidi.c:1228 snd_vmidi_output_work+0x2ac/0x5b0 sound/core/seq/seq_virmidi.c:159 process_one_work+0x1605/0x1f40 kernel/workqueue.c:2153 worker_thread+0x11a2/0x2590 kernel/workqueue.c:2296 kthread+0x465/0x4a0 kernel/kthread.c:247 ret_from_fork+0x35/0x40 arch/x86/entry/entry_64.S:416
Uninit was created at: kmsan_save_stack_with_flags mm/kmsan/kmsan.c:256 [inline] kmsan_internal_poison_shadow+0xb8/0x1b0 mm/kmsan/kmsan.c:181 kmsan_kmalloc+0x98/0x100 mm/kmsan/kmsan_hooks.c:91 __kmalloc_node+0x7bf/0x11c0 mm/slub.c:3828 kmalloc_node include/linux/slab.h:555 [inline] kvmalloc_node+0x19d/0x3e0 mm/util.c:423 kvmalloc include/linux/mm.h:577 [inline] snd_rawmidi_runtime_create sound/core/rawmidi.c:132 [inline] open_substream+0x3c8/0xaa0 sound/core/rawmidi.c:276 rawmidi_open_priv+0x347/0x1000 sound/core/rawmidi.c:327 snd_rawmidi_open+0x7d4/0x1120 sound/core/rawmidi.c:424 soundcore_open+0x9be/0xa60 sound/sound_core.c:597 chrdev_open+0xc26/0xdb0 fs/char_dev.c:417 do_dentry_open+0xce6/0x1740 fs/open.c:771 vfs_open+0xaf/0xe0 fs/open.c:880 do_last fs/namei.c:3418 [inline] path_openat+0x1799/0x6870 fs/namei.c:3534 do_filp_open+0x259/0x610 fs/namei.c:3564 do_sys_open+0x630/0x940 fs/open.c:1063 __do_sys_open fs/open.c:1081 [inline] __se_sys_open+0xad/0xc0 fs/open.c:1076 __x64_sys_open+0x4a/0x70 fs/open.c:1076 do_syscall_64+0xb8/0x100 arch/x86/entry/common.c:291 entry_SYSCALL_64_after_hwframe+0x63/0xe7 ==================================================================