Re: [syzbot] BUG: MAX_LOCKDEP_KEYS too low! (2)
From: Dmitry Vyukov <dvyukov@google.com>
Date: 2021-05-19 20:09:54
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On Wed, May 19, 2021 at 9:58 PM Randy Dunlap [off-list ref] wrote:
On 5/19/21 12:48 PM, Dmitry Vyukov wrote:quoted
On Wed, May 19, 2021 at 7:35 PM syzbot [off-list ref] wrote:quoted
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:quoted
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.