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

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Message-ID: <20130227150733.GB22383@htj.dyndns.org>
Date:	Wed, 27 Feb 2013 07:07:33 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Sedat Dilek <sedat.dilek@...il.com>
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 ? ]

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
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