linux-kernel - Re: [next-20130227] kernel NULL pointer dereference [ watchdog

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Message-ID: <CA+icZUUQPmo+dNRA2W_QMJ9zSwYPpqMMnr5brmE==TzG9bS8sw@mail.gmail.com>
Date:	Thu, 28 Feb 2013 08:27:36 +0100
From:	Sedat Dilek <sedat.dilek@...il.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Borislav Petkov <bp@...en8.de>, Wim Van Sebroeck <wim@...ana.be>,
	Ingo Molnar <mingo@...hat.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	linux-watchdog@...r.kernel.org, x86@...nel.org,
	LKML <linux-kernel@...r.kernel.org>,
	linux-next <linux-next@...r.kernel.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [next-20130227] kernel NULL pointer dereference [ watchdog | perf
 related ? ]

On Thu, Feb 28, 2013 at 8:24 AM, Sedat Dilek <sedat.dilek@...il.com> wrote:
> On Wed, Feb 27, 2013 at 4:07 PM, Tejun Heo <tj@...nel.org> wrote:
>> Replying here too just in case.
>>
>> On Wed, Feb 27, 2013 at 02:08:40PM +0100, Sedat Dilek wrote:
>>> >> static inline void *idr_find(struct idr *idr, int id)
>>> >> {
>>> >>         struct idr_layer *hint = rcu_dereference_raw(idr->hint);
>>> >>     86d7:       48 8b 05 00 00 00 00    mov    0x0(%rip),%rax        # 86de <perf_init_event+0x2e>
>>> >>                         86da: R_X86_64_PC32     .bss+0xfc
>>> >>
>>> >>         if ((id & ~IDR_MASK) == hint->prefix)
>>> >>     86de:       89 f2                   mov    %esi,%edx
>>> >>     86e0:       30 d2                   xor    %dl,%dl
>>> >>     86e2:       3b 10                   cmp    (%rax),%edx              <--- trapping insn
>>> >>     86e4:       74 4a                   je     8730 <perf_init_event+0x80>
>>> >>                 return rcu_dereference_raw(hint->ary[id & IDR_MASK]);
>>> >>
>>> >>
>>> >> So 'hint' is NULL as RAX above confirms and we're not supposed to deref
>>> >> NULL things.
>>> >>
>>> >> Looking at 29cf29e1fbb875019713eb55cf27ec35f1e5fa5e, Tejun should
>>> >> probably know. CCed.
>>
>> Fix was posted some days ago.
>>
>>   http://thread.gmane.org/gmane.linux.kernel.next/26213
>>
>> I got Andrew's patch added to -mm message a week ago.  Not sure why it
>> still hasn't showed up.  Andrew, any ideas?
>>
>> Thanks.
>>
>> --
>> tejun
>
> AFAICS the updated (correct) patch "idr: implement lookup hint" is now
> in mainline.
>

...but not in next-20130228 yet (tomorrow's Linux-Next will have it).

- Sedat -

> - Sedat -
>
> [1] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commitdiff;h=0ffc2a9c8072969253a20821c2c733a2cbb4c7c7
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