[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <20140709133138.c523aa03883be5417a4d19a4@linux-foundation.org>
Date: Wed, 9 Jul 2014 13:31:38 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: Sasha Levin <sasha.levin@...cle.com>,
David Rientjes <rientjes@...gle.com>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>,
Al Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>,
Dave Jones <davej@...hat.com>,
LKML <linux-kernel@...r.kernel.org>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: fs: use after free in /proc/pid/mountinfo
On Wed, 9 Jul 2014 16:24:06 +0200 Heiko Carstens <heiko.carstens@...ibm.com> wrote:
> 058504edd026 ("fs/seq_file: fallback to vmalloc allocation") is suspected to
> cause a crash. Actually I can't reprocude the crash nor would I be able to
> tell how the commit could cause the crash.
> Anyway, I'll be offline for the next 2.5 weeks. So if Sasha could confirm
> that reverting the patch actually does fix the crash, please revert the
> commit, unless somebody else can make sense of the report of course.
>
> I'm still wondering how Sasha could reproduce the crash.
This really sucks :(
I suppose I'll queue up a revert of 058504edd026 as a for-3.16 bandaid.
Sasha, it would be great if you could delve a bit further into this,
see if we can identify a way for others to reproduce the bug.
Did you test that little patchlet which Heiko sent?
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -34,12 +34,7 @@ static void seq_set_overflow(struct seq_file *m)
static void *seq_buf_alloc(unsigned long size)
{
- void *buf;
-
- buf = kmalloc(size, GFP_KERNEL | __GFP_NOWARN);
- if (!buf && size > PAGE_SIZE)
- buf = vmalloc(size);
- return buf;
+ return kmalloc(size, GFP_KERNEL);
}
/**
It would also be interesting to try the opposite: always use vmalloc().
That may make it easier to trigger the bug.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists