On Mon, Sep 24, 2018 at 3:19 PM, Jiri Kosina <jikos@xxxxxxxxxx> wrote: > On Sun, 16 Sep 2018, Amir Goldstein wrote: > >> > > syzbot found the following crash on: >> > > >> > > HEAD commit: 11da3a7f84f1 Linux 4.19-rc3 >> > > git tree: upstream >> > > console output: https://syzkaller.appspot.com/x/log.txt?x=141ffbca400000 >> > > kernel config: https://syzkaller.appspot.com/x/.config?x=9917ff4b798e1a1e >> > > dashboard link: https://syzkaller.appspot.com/bug?extid=6fb572170402d311dd39 >> > > compiler: gcc (GCC) 8.0.1 20180413 (experimental) >> > > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=136a60ae400000 >> > > >> > > IMPORTANT: if you fix the bug, please add the following tag to the commit: >> > > Reported-by: syzbot+6fb572170402d311dd39@xxxxxxxxxxxxxxxxxxxxxxxxx >> > > >> > >> > Since it kept printk()ing for at least 93 seconds, it might have kept for 150 seconds. >> > >> > [ 174.614333] hid-generic 0000:0000:0000.0003: unknown main item tag 0x0 >> > [ 268.196102] INFO: task kworker/u4:1:23 blocked for more than 140 seconds. >> > >> > Since the reproducer is simple, this might be lockup due to continuous printk(). >> > If syzbot can reliably reproduce this problem using the reproducer, try >> > ratelimiting printk(). >> >> Right.. and I was able to reproduce after setting CONFIG_HID_GENERIC=y >> but unless I am missing something, the core problem doesn't seem related to >> fsnotify and $SUBJECT, so CCing HID maintainer. > > Alright, so you're basically triggering a never-ending flow of kmsgs being > printed out from HID parser due to doing crazy things with the parser, and > that causes the issues for the kworker trying to flush them out. > > I guess the patch below fixes it, however the kworker should not really be > blocked by this I think ... adding a few more printk folks to double-check > why the kworker would get stuck due to massive printk() flood. The task hanged in synchronize_rcu(). I think any infinite loop (whether it prints or not) can cause this. > diff --git a/include/linux/hid.h b/include/linux/hid.h > index d44a78362942..b81332fe85a4 100644 > --- a/include/linux/hid.h > +++ b/include/linux/hid.h > @@ -1157,22 +1157,22 @@ do { \ > } while (0) > > #define hid_printk(level, hid, fmt, arg...) \ > - dev_printk(level, &(hid)->dev, fmt, ##arg) > + dev_printk_ratelimited(level, &(hid)->dev, fmt, ##arg) > #define hid_emerg(hid, fmt, arg...) \ > - dev_emerg(&(hid)->dev, fmt, ##arg) > + dev_emerg_ratelimited(&(hid)->dev, fmt, ##arg) > #define hid_crit(hid, fmt, arg...) \ > - dev_crit(&(hid)->dev, fmt, ##arg) > + dev_crit_ratelimited(&(hid)->dev, fmt, ##arg) > #define hid_alert(hid, fmt, arg...) \ > - dev_alert(&(hid)->dev, fmt, ##arg) > + dev_alert_ratelimited(&(hid)->dev, fmt, ##arg) > #define hid_err(hid, fmt, arg...) \ > - dev_err(&(hid)->dev, fmt, ##arg) > + dev_err_ratelimited(&(hid)->dev, fmt, ##arg) > #define hid_notice(hid, fmt, arg...) \ > - dev_notice(&(hid)->dev, fmt, ##arg) > + dev_notice_ratelimited(&(hid)->dev, fmt, ##arg) > #define hid_warn(hid, fmt, arg...) \ > - dev_warn(&(hid)->dev, fmt, ##arg) > + dev_warn_ratelimited(&(hid)->dev, fmt, ##arg) > #define hid_info(hid, fmt, arg...) \ > - dev_info(&(hid)->dev, fmt, ##arg) > + dev_info_ratelimited(&(hid)->dev, fmt, ##arg) > #define hid_dbg(hid, fmt, arg...) \ > - dev_dbg(&(hid)->dev, fmt, ##arg) > + dev_dbg_ratelimited(&(hid)->dev, fmt, ##arg) > > #endif > > -- > Jiri Kosina > SUSE Labs > > -- > You received this message because you are subscribed to the Google Groups "syzkaller-bugs" group. > To unsubscribe from this group and stop receiving emails from it, send an email to syzkaller-bugs+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/nycvar.YFH.7.76.1809241511500.15880%40cbobk.fhfr.pm. > For more options, visit https://groups.google.com/d/optout.
