linux-ext4 - Re: pagefault in generic_file_buffered

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

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <455B5A7B.6010807@us.ibm.com>
Date:	Wed, 15 Nov 2006 10:20:43 -0800
From:	Badari Pulavarty <pbadari@...ibm.com>
To:	Andrew Morton <akpm@...l.org>
CC:	linux-mm <linux-mm@...ck.org>, ext4 <linux-ext4@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: pagefault in generic_file_buffered_write() causing deadlock

Andrew Morton wrote:
> On Wed, 15 Nov 2006 07:57:45 -0800
> Badari Pulavarty <pbadari@...ibm.com> wrote:
>
>   
>> We are looking at a customer situation (on 2.6.16-based distro) - where
>> system becomes almost useless while running some java & stress tests.
>>
>> Root cause seems to be taking a pagefault in generic_file_buffered_write
>> () after calling prepare_write. I am wondering 
>>
>> 1) Why & How this can happen - since we made sure to fault the user
>> buffer before prepare write.
>>     
>
> When using writev() we only fault in the first segment of the iovec.  If
> the second or succesive segment isn't mapped into pagetables we're
> vulnerable to the deadlock.
>
>   
Hmm.. Not it :(
Its coming from write() not writev().

[C00000002ABBF290] [C00000000039D58C] .do_page_fault+0x2e4/0x75c
[C00000002ABBF460] [C000000000004860] .handle_page_fault+0x20/0x54
--- Exception: 301 at .__copy_tofrom_user+0x11c/0x580
    LR = .generic_file_buffered_write+0x39c/0x7c8
[C00000002ABBF750] [C000000000095A94]
.generic_file_buffered_write+0x2c0/0x7c8 (
unreliable)
[C00000002ABBF8F0] [C0000000000962EC]
.__generic_file_aio_write_nolock+0x350/0x3
e0
[C00000002ABBFA20] [C000000000096908] .generic_file_aio_write+0x78/0x104
[C00000002ABBFAE0] [C0000000001649F0] .ext3_file_write+0x2c/0xd4
[C00000002ABBFB70] [C0000000000C5168] .do_sync_write+0xd4/0x130
[C00000002ABBFCF0] [C0000000000C5ED4] .vfs_write+0x128/0x20c
[C00000002ABBFD90] [C0000000000C664C] .sys_write+0x4c/0x8c
[C00000002ABBFE30] [C00000000000871C] syscall_exit+0x0/0x40

Thanks,
Badari

-
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html