linux-kernel - Re: Crash (ext3 ) during 2.6.29-rc6 boot

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Date:	Wed, 25 Feb 2009 14:31:20 +0100 (CET)
From:	Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com>
To:	Mark Nelson <markn@....ibm.com>
cc:	linuxppc-dev@...abs.org, Jan Kara <jack@....cz>,
	Jan Kara <jack@...e.cz>, Mel Gorman <mel@....ul.ie>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-ext4@...r.kernel.org
Subject: Re: Crash (ext3 ) during 2.6.29-rc6 boot

On Wed, 25 Feb 2009, Mark Nelson wrote:
> On Wed, 25 Feb 2009 08:50:46 pm Geert Uytterhoeven wrote:
> > On Wed, 25 Feb 2009, Mark Nelson wrote:
> > > On Tue, 24 Feb 2009 05:38:37 pm Sachin P. Sant wrote:
> > > > Jan Kara wrote:
> > > > >   Hmm, OK. But then I'm not sure how that can happen. Obviously, memcpy
> > > > > somehow got beyond end of the page referenced by bh->b_data. So it means
> > > > > that le16_to_cpu(entry->e_value_offs) + size > page_size. But
> > > > > ext3_xattr_find_entry() calls ext3_xattr_check_entry() which in
> > > > > particular checks whether e_value_offs + e_value_size isn't greater than
> > > > > bh->b_size. So I see no way how memcpy can get beyond end of the page.
> > > > >   Sachin, is the problem reproducible? If yes, can you send us contents
> > > > >   
> > > > Yes, i am able to recreate this problem easily. As i had mentioned if the
> > > > earlier kernel is booted with selinux enabled and then 2.6.29-rc6 is booted
> > > > i get this crash. But if i specify selinux=0 at command line, 2.6.29-rc6 boots
> > > > without any problem.
> > > 
> > > Hi Sanchin and Geert,
> > > 
> > > Does the patch below fix the problems you're seeing? If it does I'll send
> > > a properly written up and formatted patch to linuxppc-dev (as well as
> > > another one to fix the same problem in copy_tofrom_user()).
> > 
> > Unfortunately not, now it crashes while accessing the memory pointed to by
> > GPR16, in
> > 
> > NIP: copy_page_range+x0608/0x628
> > LR:  dup_mm+0x2e4/0x428
> > Trace: debug_table+0xcc70/0x1afe0 (unreliable)
> > dup_mm+0x2e4/0x428
> > copy_process+0x86c/0xf9c
> > do_fork+0x188/0x39c
> > sys_clone+0x58/0x70
> > ppc_clone+0x8/0xc
> > 
> > However, after reverting 25d6e2d7c58ddc4a3b614fc5381591c0cfe66556, I still see
> > similar problems as above (crash in copy_page_range()).
> > Which makes me think that
> >   1. Your new patch fixes the problem introduced by 25d6e2d7,
> >   2. There's still another issue than the one introduced by 25d6e2d7.
> 
> Does the following patch fix the errors you're seeing? (it applies the
> same fix as the previous patch but this time to copy_tofrom_user, which
> I updated in a4e22f02f5b6518c1484faea1f88d81802b9feac)

Thanks, but I still get crashes in copy_page_range().

With kind regards,

Geert Uytterhoeven
Software Architect

Sony Techsoft Centre Europe
The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium

Phone:    +32 (0)2 700 8453
Fax:      +32 (0)2 700 8622
E-mail:   Geert.Uytterhoeven@...ycom.com
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