From: Minchan Kim <minchan@kernel.org>
To: Nitin Gupta <ngupta@vflare.org>
Cc: Greg KH <greg@kroah.com>,
Seth Jennings <sjenning@linux.vnet.ibm.com>,
Dan Carpenter <dan.carpenter@oracle.com>,
Sam Hansen <solid.se7en@gmail.com>, Tomas M <tomas@slax.org>,
Mihail Kasadjikov <hamer.mk@gmail.com>,
Linux Driver Project <devel@linuxdriverproject.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] zram: Prevent use of unmapped buffer
Date: Wed, 28 Nov 2012 14:15:05 +0900 [thread overview]
Message-ID: <20121128051505.GD23136@blaptop> (raw)
In-Reply-To: <1354001167-24878-1-git-send-email-ngupta@vflare.org>
Hi Nitin,
On Mon, Nov 26, 2012 at 11:26:07PM -0800, Nitin Gupta wrote:
> The commit c8f2f0db1 ("zram: Fix handling of incompressible pages")
> introduced a bug which caused a kunmap()'ed buffer to be used in case
I got confused by the descripton. :(
The descripton is not right.
The problem is to access freed memory, not accessing to kunmaped buffer.
partial I/O write.
1. uncmem = kmalloc
2. zram_decompress_page(uncmem)
3. memcpy(uncmem, user_mem)
4. lzo1x_1_compress(uncmem)
5. kfree(uncmem)
6. src = uncmem
7. memcpy(cmem, src, clen) <----- HIT
> of partial writes where the data was found to be incompressible.
>
> This fixes bug 50081:
> https://bugzilla.kernel.org/show_bug.cgi?id=50081
>
> Signed-off-by: Nitin Gupta <ngupta@vflare.org>
> Reported-by: Mihail Kasadjikov <hamer.mk@gmail.com>
> Reported-by: Tomas M <tomas@slax.org>
Good catch! Shame on me. I should have reivewed more carefully. :(
Please resend it with revised descrption and title.
I will rebase mh patchset just sent on top of this bug fix patch.
P.S) Sigh, Now code isn't clean due to partial read/write path handling.
IMHO, sooner or later, we need refactoring.
--
Kind regards,
Minchan Kim
next prev parent reply other threads:[~2012-11-28 5:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-27 7:26 [PATCH] zram: Prevent use of unmapped buffer Nitin Gupta
2012-11-27 7:52 ` Tomas M
2012-11-28 5:15 ` Minchan Kim [this message]
2012-11-29 1:33 ` Minchan Kim
2012-11-29 1:45 ` Nitin Gupta
2012-11-29 2:08 ` Minchan Kim
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