Messages in this thread | | | Date | Mon, 03 Sep 2018 06:22:42 -0700 | Subject | Re: Re: KMSAN: uninit-value in snd_midi_event_encode_byte | From | syzbot <> |
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> 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@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 >> ==================================================================
> 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.
> Takashi
> -- 8< -- > From: Takashi Iwai <tiwai@suse.de> > Subject: [PATCH] ALSA: rawmidi: Initialize allocated buffers
> syzbot reported the uninitialized value exposure in certain situations > using virmidi loop. It's likely a very small race at writing and > reading, and the influence is almost negligible. But it's safer to > paper over this just by replacing the existing kvmalloc() with > kvzalloc().
> Reported-by: syzbot+194dffdb8b22fc5d207a@syzkaller.appspotmail.com > Signed-off-by: Takashi Iwai <tiwai@suse.de> > --- > sound/core/rawmidi.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-)
> diff --git a/sound/core/rawmidi.c b/sound/core/rawmidi.c > index 69517e18ef07..08d5662039e3 100644 > --- a/sound/core/rawmidi.c > +++ b/sound/core/rawmidi.c > @@ -129,7 +129,7 @@ static int snd_rawmidi_runtime_create(struct > snd_rawmidi_substream *substream) > runtime->avail = 0; > else > runtime->avail = runtime->buffer_size; > - runtime->buffer = kvmalloc(runtime->buffer_size, GFP_KERNEL); > + runtime->buffer = kvzalloc(runtime->buffer_size, GFP_KERNEL); > if (!runtime->buffer) { > kfree(runtime); > return -ENOMEM; > @@ -655,7 +655,7 @@ static int resize_runtime_buffer(struct > snd_rawmidi_runtime *runtime, > if (params->avail_min < 1 || params->avail_min > params->buffer_size) > return -EINVAL; > if (params->buffer_size != runtime->buffer_size) { > - newbuf = kvmalloc(params->buffer_size, GFP_KERNEL); > + newbuf = kvzalloc(params->buffer_size, GFP_KERNEL); > if (!newbuf) > return -ENOMEM; > spin_lock_irq(&runtime->lock); > -- > 2.18.0
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