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From: Heiko Carstens <hca@linux.ibm.com>
To: Vasily Gorbik <gor@linux.ibm.com>
Cc: Alexander Egorenkov <egorenar@linux.ibm.com>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Nick Terrell <terrelln@fb.com>,
	linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-mips@vger.kernel.org
Subject: Re: [PATCH 1/1] s390/decompressor: specify __decompress() buf len to avoid overflow
Date: Mon, 30 Jan 2023 16:15:55 +0100	[thread overview]
Message-ID: <Y9ffKxhKv8Gan34Z@osiris> (raw)
In-Reply-To: <patch-1.thread-41c676.git-41c676c2d153.your-ad-here.call-01675030179-ext-9637@work.hours>

On Sun, Jan 29, 2023 at 11:47:23PM +0100, Vasily Gorbik wrote:
> Historically calls to __decompress() didn't specify "out_len" parameter
> on many architectures including s390, expecting that no writes beyond
> uncompressed kernel image are performed. This has changed since commit
> 2aa14b1ab2c4 ("zstd: import usptream v1.5.2") which includes zstd library
> commit 6a7ede3dfccb ("Reduce size of dctx by reutilizing dst buffer
> (#2751)"). Now zstd decompression code might store literal buffer in
> the unwritten portion of the destination buffer. Since "out_len" is
> not set, it is considered to be unlimited and hence free to use for
> optimization needs. On s390 this might corrupt initrd or ipl report
> which are often placed right after the decompressor buffer. Luckily the
> size of uncompressed kernel image is already known to the decompressor,
> so to avoid the problem simply specify it in the "out_len" parameter.
> 
> Link: https://github.com/facebook/zstd/commit/6a7ede3dfccb
> Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
> ---
>  arch/s390/boot/decompressor.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)

Applied, thanks!

      parent reply	other threads:[~2023-01-30 15:16 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-29 22:47 [PATCH 0/1] s390: fix initrd corruption in decompressor with new zstd version Vasily Gorbik
2023-01-29 22:47 ` [PATCH 1/1] s390/decompressor: specify __decompress() buf len to avoid overflow Vasily Gorbik
2023-01-30 14:41   ` Alexander Egorenkov
2023-01-30 15:15   ` Heiko Carstens [this message]

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