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Message-ID: <1519962555.10510.1.camel@intel.com>
Date: Fri, 2 Mar 2018 03:48:40 +0000
From: "Hao, Shun" <shun.hao@...el.com>
To: "dvyukov@...gle.com" <dvyukov@...gle.com>,
"sergey.senozhatsky@...il.com" <sergey.senozhatsky@...il.com>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"peterz@...radead.org" <peterz@...radead.org>,
"rostedt@...dmis.org" <rostedt@...dmis.org>,
"torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
"penguin-kernel@...ove.sakura.ne.jp"
<penguin-kernel@...ove.sakura.ne.jp>,
"vbabka@...e.cz" <vbabka@...e.cz>,
"xiyou.wangcong@...il.com" <xiyou.wangcong@...il.com>,
"pavel@....cz" <pavel@....cz>,
"hannes@...xchg.org" <hannes@...xchg.org>,
"kasan-dev@...glegroups.com" <kasan-dev@...glegroups.com>,
"pmladek@...e.com" <pmladek@...e.com>,
"mhocko@...nel.org" <mhocko@...nel.org>,
"byungchul.park@....com" <byungchul.park@....com>,
"Hansen, Dave" <dave.hansen@...el.com>,
"tj@...nel.org" <tj@...nel.org>,
"mgorman@...e.de" <mgorman@...e.de>, "lkp@...org" <lkp@...org>,
"mathieu.desnoyers@...icios.com" <mathieu.desnoyers@...icios.com>,
"jack@...e.cz" <jack@...e.cz>
Subject: Re: [lkp-robot] [printk] c162d5b433: BUG:KASAN:use-after-scope_in_c
sorry for missing the attached script in original mail, here to add it.
On Thu, 2018-03-01 at 08:47 +0000, Dmitry Vyukov wrote:
> On Thu, Mar 1, 2018 at 2:37 AM, Sergey Senozhatsky
> <sergey.senozhatsky@...il.com> wrote:
> > Hello,
> >
> > Cc-ing Dmitry Vyukov and kasan-dev on this.
> >
> > On (02/28/18 16:59), Petr Mladek wrote:
> > [..]
> > > > >
> > > > > [ 0.003333] BUG: KASAN: use-after-scope in
> > > > > console_unlock+0x185/0x960
> > > > > [ 0.003333] BUG: KASAN: use-after-scope in
> > > > > console_unlock+0x185/0x960
> > > >
> > > > Is there any change to get disassembly of console_unlock() from
> > > > the
> > > > problematic build?
> > > >
> > > > I have troubles to reproduce this myself. Also I was not able
> > > > to find any
> > > > bug just by looking into the code yet. The disassembly might
> > > > help
> > > > a lot here.
> > > >
> > > >
> > > > Interesting symptoms (for myself and other debuggers):
> > > >
> > > > The lines are duplicated. Therefore it happened when real
> > > > console was registered and before the early console was
> > > > unregistered.
> > > > See also the full dmesg for these actions. The related printk
> > > > messages
> > > > are right after the KASAN report.
> > > >
> > > > I wonder if it is unsafe to pass the console_lock via
> > > > console_trylock_spinnning() from console_unlock() called
> > > > in register_console(). I do not see any problem but I might
> > > > be blind.
> >
> > I'm not sure it we actually have concurrent printks at that state
> > yet,
> > might be too early for any printk offloading. The backtrace still
> > makes no sense to me at all, tho. We had this report twice,
> > probably,
> > already (even before the offloading patchset, if I'm not mistaken).
> >
> > https://marc.info/?l=linux-kernel&m=151200883525299
> >
> > [..]
> > > I feel lost a bit.
> >
> > Yeah... can't understand what's going on there.
> >
> > The last time kasan didn't like this part
> >
> > [ 0.003333] ? console_unlock+0x605/0xcc0:
> > atomic_read at
> > arch/x86/include/asm/atomic.h:27
> > (inlined by) static_key_count at
> > include/linux/jump_label.h:191
> > (inlined by) static_key_false at
> > include/linux/jump_label.h:201
> > (inlined by) trace_console_rcuidle
> > at include/trace/events/printk.h:10
> > (inlined by) call_console_drivers at
> > kernel/printk/printk.c:1556
> > (inlined by) console_unlock at
> > kernel/printk/printk.c:2233
> >
> > complaining that there was a write of size 4... at atomic_read().
> >
> > Now it's reporting that the write of size 1 was out of scope.
> >
> > > I am really curious what code is proceed on the line
> > > console_unlock+0x185/0x960.
> >
> > Agreed.
> >
> > On my system 0x185/0x960 is somewhere around
> >
> >
> > 191e: 89 d7 mov %edx,%edi
> > 1920: e8 06 e7 ff ff callq 2b <log_next>
> > 1925: 48 89 2d 00 00 00
> > 00 mov %rbp,0x0(%rip) # 192c <console_unlock+0x17f>
> > 192c: 89 05 00 00 00
> > 00 mov %eax,0x0(%rip) # 1932 <console_unlock+0x185>
> > > > 1932: eb a9 jmp 18dd
> > > > <console_unlock+0x130>
> >
> > 1934: 8b 35 00 00 00
> > 00 mov 0x0(%rip),%esi # 193a <console_unlock+0x18d>
> > 193a: b9 00 04 00 00 mov $0x400,%ecx
> > 193f: 4c 89 ef mov %r13,%rdi
> > 1942: 31 ed xor %ebp,%ebp
> >
> >
> > That jmp 18dd after log_next() is a `goto skip' in
> > suppress_message_printing() branch
> >
> > skip:
> > if (console_seq == log_next_seq)
> > break;
> >
> > msg = log_from_idx(console_idx);
> > if (suppress_message_printing(msg->level)) {
> > /*
> > * Skip record we have buffered and already
> > printed
> > * directly to the console when we received
> > it, and
> > * record that has level above the console
> > loglevel.
> > */
> > console_idx = log_next(console_idx);
> > console_seq++;
> > > > goto skip;
> >
> > }
> >
> >
> > As far as I can tell.
>
>
> Hi Shun,
>
> The report says "job-script is attached in this email", but I don't
> see it attached. Did you forget to attach it? How can I reproduce
> this
> exact build?
> Could you post a symbolized report with inlines frames?
Download attachment "job-script" of type "application/x-shellscript" (4415 bytes)
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