On Mon, Sep 3, 2018 at 3:29 PM, Takashi Iwai <tiwai@xxxxxxx> wrote: > On Mon, 03 Sep 2018 15:22:42 +0200, > syzbot wrote: >> >> > On Mon, 03 Sep 2018 03:53:03 +0200, >> > syzbot wrote: >> >> >> 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@xxxxxxxxxxxxxxxxxxxxxxxxx >> >> >> ================================================================== >> >> 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 >> >> ================================================================== >> >> > This looks like some small race at virmidi reading and the buffer >> > handling, which should be almost harmless by itself. >> > Nevertheless, the fix should be easy, just replacing kvmalloc() with >> > kvzalloc(), as below. >> >> > Let's check whether this works. >> >> > #syz test: >> > git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git >> > topic/rawmidi-fixes >> >> KMSAN bugs can only be tested on https://github.com/google/kmsan.git tree >> because KMSAN tool is not upstreamed yet. >> See >> https://github.com/google/syzkaller/blob/master/docs/syzbot.md#kmsan-bugs >> for details. > > So how is the procedure to test a patch for bugs spotted by KMSAN? > > In this case, the fix is trivial, so I can put it to my tree for the > next pull request. Of course, it'd be better if it can be confirmed > to work beforehand... https://github.com/google/syzkaller/blob/master/docs/syzbot.md#kmsan-bugs Which means you need to attach a patch because it's not in that tree. _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
