lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Tue, 14 Sep 2021 10:08:45 +0800 From: 王贇 <yun.wang@...ux.alibaba.com> To: Dave Hansen <dave.hansen@...el.com>, Dave Hansen <dave.hansen@...ux.intel.com>, Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>, "open list:X86 MM" <linux-kernel@...r.kernel.org>, "open list:BPF (Safe dynamic programs and tools)" <netdev@...r.kernel.org>, "open list:BPF (Safe dynamic programs and tools)" <bpf@...r.kernel.org> Subject: Re: [PATCH] perf: fix panic by disable ftrace on fault.c On 2021/9/13 下午10:49, Dave Hansen wrote: > On 9/12/21 8:30 PM, 王贇 wrote: >> According to the trace we know the story is like this, the NMI >> triggered perf IRQ throttling and call perf_log_throttle(), >> which triggered the swevent overflow, and the overflow process >> do perf_callchain_user() which triggered a user PF, and the PF >> process triggered perf ftrace which finally lead into a suspected >> stack overflow. >> >> This patch disable ftrace on fault.c, which help to avoid the panic. > ... >> +# Disable ftrace to avoid stack overflow. >> +CFLAGS_REMOVE_fault.o = $(CC_FLAGS_FTRACE) > > Was this observed on a mainline kernel? Yes, it is trigger on linux-next. > > How reproducible is this? > > I suspect we're going into do_user_addr_fault(), then falling in here: > >> if (unlikely(faulthandler_disabled() || !mm)) { >> bad_area_nosemaphore(regs, error_code, address); >> return; >> } > Correct, perf_callchain_user() disabled PF which lead into here. > Then something double faults in perf_swevent_get_recursion_context(). > But, you snipped all of the register dump out so I can't quite see > what's going on and what might have caused *that* fault. But, in my > kernel perf_swevent_get_recursion_context+0x0/0x70 is: > > mov $0x27d00,%rdx > > which is rather unlikely to fault. Would you like to check the full trace I just sent see if we can get any clue? > > Either way, we don't want to keep ftrace out of fault.c. This patch is > just a hack, and doesn't really try to fix the underlying problem. This > situation *should* be handled today. There's code there to handle it. > > Something else really funky is going on. Do you think stack overflow is possible in this case? To be mentioned the NMI arrive in very high frequency, and reduce perf_event_max_sample_rate to a low value can also avoid the panic. Regards, Michael Wang >
Powered by blists - more mailing lists