linux-kernel - Re: [PATCH] incorrect error handling inside generic_file_direct

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]

Date:	Wed, 13 Dec 2006 02:14:18 +0300
From:	Dmitriy Monakhov <dmonakhov@...nvz.org>
To:	Andrew Morton <akpm@...l.org>
Cc:	Dmitriy Monakhov <dmonakhov@...nvz.org>,
	linux-kernel@...r.kernel.org,
	Linux Memory Management <linux-mm@...ck.org>,
	<devel@...nvz.org>, xfs@....sgi.com
Subject: Re: [PATCH]  incorrect error handling inside generic_file_direct_write

Andrew Morton <akpm@...l.org> writes:

> On Tue, 12 Dec 2006 16:18:32 +0300
> Dmitriy Monakhov <dmonakhov@...ru> wrote:
>
>> >> but according to filemaps locking rules: mm/filemap.c:77
>> >>  ..
>> >>  *  ->i_mutex			(generic_file_buffered_write)
>> >>  *    ->mmap_sem		(fault_in_pages_readable->do_page_fault)
>> >>  ..
>> >> I'm confused a litle bit, where is the truth? 
>> >
>> > xfs_write() calls generic_file_direct_write() without taking i_mutex for
>> > O_DIRECT writes.
>> Yes, but my quastion is about __generic_file_aio_write_nolock().
>> As i understand _nolock sufix means that i_mutex was already locked 
>> by caller, am i right ?
>
> Nope.  It just means that __generic_file_aio_write_nolock() doesn't take
> the lock.  We don't assume or require that the caller took it.  For example
> the raw driver calls generic_file_aio_write_nolock() without taking
> i_mutex.  Raw isn't relevant to the problem (although ocfs2 might be).  But
> we cannot assume that all callers have taken i_mutex, I think.
>
> I guess we can make that a rule (document it, add
> BUG_ON(!mutex_is_locked(..)) if it isn't a blockdev) if needs be.  After
> really checking that this matches reality for all callers.
I've checked generic_file_aio_write_nolock() callers for non blockdev.
Only ocfs2 call it explicitly, and do it under i_mutex.
So we need to do: 
1) Change wrong comments.
2) Add BUG_ON(!mutex_is_locked(..)) for non blkdev.
3) Invoke vmtruncate only for non blkdev.

Signed-off-by: Dmitriy Monakhov <dmonakhov@...nvz.org>
-------

View attachment "direct-io-fix.patch" of type "text/plain" (2124 bytes)