Messages in this thread | | | From | Dmitry Vyukov <> | Date | Wed, 19 May 2021 22:09:35 +0200 | Subject | Re: [syzbot] BUG: MAX_LOCKDEP_KEYS too low! (2) |
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On Wed, May 19, 2021 at 9:58 PM Randy Dunlap <rdunlap@infradead.org> wrote: > > On 5/19/21 12:48 PM, Dmitry Vyukov wrote: > > On Wed, May 19, 2021 at 7:35 PM syzbot > > <syzbot+a70a6358abd2c3f9550f@syzkaller.appspotmail.com> wrote: > >> > >> Hello, > >> > >> syzbot found the following issue on: > >> > >> HEAD commit: b81ac784 net: cdc_eem: fix URL to CDC EEM 1.0 spec > >> git tree: net > >> console output: https://syzkaller.appspot.com/x/log.txt?x=15a257c3d00000 > >> kernel config: https://syzkaller.appspot.com/x/.config?x=5b86a12e0d1933b5 > >> dashboard link: https://syzkaller.appspot.com/bug?extid=a70a6358abd2c3f9550f > >> > >> 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+a70a6358abd2c3f9550f@syzkaller.appspotmail.com > >> > >> BUG: MAX_LOCKDEP_KEYS too low! > > > > include/linux/lockdep.h > > #define MAX_LOCKDEP_KEYS_BITS 13 > #define MAX_LOCKDEP_KEYS (1UL << MAX_LOCKDEP_KEYS_BITS)
Ouch, so it's not configurable yet :( Unless, of course, we identify the offender that produced thousands of lock classes in the log and fix it.
> Documentation/locking/lockdep-design.rst: > > Troubleshooting: > ---------------- > > The validator tracks a maximum of MAX_LOCKDEP_KEYS number of lock classes. > Exceeding this number will trigger the following lockdep warning:: > > (DEBUG_LOCKS_WARN_ON(id >= MAX_LOCKDEP_KEYS)) > > By default, MAX_LOCKDEP_KEYS is currently set to 8191, and typical > desktop systems have less than 1,000 lock classes, so this warning > normally results from lock-class leakage or failure to properly > initialize locks. These two problems are illustrated below: > > > > > What config controls this? I don't see "MAX_LOCKDEP_KEYS too low" in > > any of the config descriptions... > > Here is what syzbot used: > > > > CONFIG_LOCKDEP=y > > CONFIG_LOCKDEP_BITS=16 > > CONFIG_LOCKDEP_CHAINS_BITS=17 > > CONFIG_LOCKDEP_STACK_TRACE_BITS=20 > > CONFIG_LOCKDEP_STACK_TRACE_HASH_BITS=14 > > CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS=12 > > > > We already bumped most of these. > > The log contains dump of the lockdep debug files, is there any offender? > > > > Also looking at the log I noticed a memory safety bug in lockdep implementation: > > ... > > -- > ~Randy > > -- > 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@googlegroups.com. > To view this discussion on the web visit https://groups.google.com/d/msgid/syzkaller-bugs/c545268c-fe62-883c-4c46-974b3bb3cea1%40infradead.org.
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