Re: Fwd: [STABLE CHERRYPICK] ext4: avoid modifying checksum fields directly during checksum verification

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Sep 08, 2016 at 10:21:34AM +0300, Török Edwin wrote:
> Hi,
> 
> Not sure if this was sent to the right place: stable@kernel.org
> doesn't seem to exist, I can't find this message in the ML archives,
> or the 4.7.3 changelog.  Could you please include this in 4.7.4, I've
> been waiting for this patch to get included ever since 4.7.1...

Yeah, I never saw it.

Will add it to the queue, it's long, might take a release or two to make
it...

Were there any objections from the ext4 maintainers in taking the patch
below?

thanks,

greg k-h

> -------- Forwarded Message --------
> Subject: [STABLE CHERRYPICK] ext4: avoid modifying checksum fields directly during checksum verification
> Date: Mon, 5 Sep 2016 22:29:55 -0400
> From: Theodore Ts'o <tytso@mit.edu>
> To: stable@kernel.org
> CC: linux-ext4@vger.kernel.org, Török Edwin <edwin@etorok.net>
> 
> Hi, please cherry pick the following commit into the stable kernels.
> The commit landed in 4.8-rc1.  It wasn't marked with a cc:
> stable@kernel.org, but it should be backported since it affecting a
> number of users who are trying to use ext4's metadata checksum
> feature.
> 
> Thanks!!
> 
> commit b47820edd1634dc1208f9212b7ecfb4230610a23
> Author: Daeho Jeong <daeho.jeong@samsung.com>
> Date:   Sun Jul 3 17:51:39 2016 -0400
> 
>     ext4: avoid modifying checksum fields directly during checksum verification
>     
>     We temporally change checksum fields in buffers of some types of
>     metadata into '0' for verifying the checksum values. By doing this
>     without locking the buffer, some metadata's checksums, which are
>     being committed or written back to the storage, could be damaged.
>     In our test, several metadata blocks were found with damaged metadata
>     checksum value during recovery process. When we only verify the
>     checksum value, we have to avoid modifying checksum fields directly.
>     
>     Signed-off-by: Daeho Jeong <daeho.jeong@samsung.com>
>     Signed-off-by: Youngjin Gil <youngjin.gil@samsung.com>
>     Signed-off-by: Theodore Ts'o <tytso@mit.edu>
>     Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
> 
> 						- Ted
> 						
> 
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