This is a note to let you know that I've just added the patch titled s390/decompressor: specify __decompress() buf len to avoid overflow to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: s390-decompressor-specify-__decompress-buf-len-to-av.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit a25bcb25f9ec18e62ea124749616a820d0d74fbd Author: Vasily Gorbik <gor@xxxxxxxxxxxxx> Date: Sun Jan 29 23:47:23 2023 +0100 s390/decompressor: specify __decompress() buf len to avoid overflow [ Upstream commit 7ab41c2c08a32132ba8c14624910e2fe8ce4ba4b ] 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@xxxxxxxxxxxxx> Tested-by: Alexander Egorenkov <egorenar@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/patch-1.thread-41c676.git-41c676c2d153.your-ad-here.call-01675030179-ext-9637@work.hours Signed-off-by: Heiko Carstens <hca@xxxxxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/arch/s390/boot/compressed/decompressor.c b/arch/s390/boot/compressed/decompressor.c index e27c2140d6206..623f6775d01d7 100644 --- a/arch/s390/boot/compressed/decompressor.c +++ b/arch/s390/boot/compressed/decompressor.c @@ -80,6 +80,6 @@ void *decompress_kernel(void) void *output = (void *)decompress_offset; __decompress(_compressed_start, _compressed_end - _compressed_start, - NULL, NULL, output, 0, NULL, error); + NULL, NULL, output, vmlinux.image_size, NULL, error); return output; }