Thanks for the tip! Doug Anderson <dianders@xxxxxxxxxxxx> 于2025年1月9日周四 01:33写道： > > Hi, > > On Sun, Dec 22, 2024 at 10:32 PM wzs <wangzhengshu39@xxxxxxxxx> wrote: > > > > Hello, > > when fuzzing the Linux kernel, > > I triggered many "watch: BUG: soft lockup" warnings. > > I am not sure whether this is an issue with the kernel or with the > > fuzzing program I ran. > > (The same fuzzing program, when tested on kernel versions from > > Linux-6.7.0 to 6.12.0, triggers the 'watchdog: BUG: soft lockup' > > warning on some versions, while others do not. Linux 6.12.0 is the > > latest stable release where this error occurs.) > > > > The bug information I provided below is from the Linux-6.12.0 kernel. > > If you need bug information from other versions, I would be happy to provide it. > > > > kernel config :https://pastebin.com/i4LPXNAN > > console output :https://pastebin.com/uKVpvJ78 > > IMO it's nearly always a bug if userspace can cause the kernel to soft > lockup. I'd expect this isn't a bug in the soft lockup detector but a > problem in whatever part of the kernel you're fuzzing. For some > details of the soft lockup detector, see > `Documentation/admin-guide/lockup-watchdogs.rst`. > > Presumably you're fuzzing the kernel in a way that causes it to enter > a big loop while preemption is disabled, or something like that. > Presumably the kernel should be detecting something invalid that > userspace did and that would keep it from looping so long. > > I tried looking at your pastebin and probably what's going on is > somewhere hidden in there, but unfortunately the beginning of the logs > are a bit jumbled since it looks like the RCU warning and the soft > lockup warning happened at about the same time and their stuff is > jumbled. There's also a lot of tasks to go through. Honestly, it's > probably less work just to look at whatever you were trying to fuzz to > help you pinpoint the problem. > > I'll also note that you seem to be using KASAN and are running in a > virtual machine. It's not inconceivable that's contributing to your > problems. KASAN makes things _a lot_ slower and a VM may be getting > its time stolen by the host. > > -Doug
