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| H A D | dasd_eckd.c | cd68c48e Thu May 05 09:17:31 CDT 2022 Jan Höppner <hoeppner@linux.ibm.com> s390/dasd: Fix read for ESE with blksize < 4k
When reading unformatted tracks on ESE devices, the corresponding memory
areas are simply set to zero for each segment. This is done incorrectly
for blocksizes < 4096.
There are two problems. First, the increment of dst is done using the
counter of the loop (off), which is increased by blksize every
iteration. This leads to a much bigger increment for dst as actually
intended. Second, the increment of dst is done before the memory area
is set to 0, skipping a significant amount of bytes of memory.
This leads to illegal overwriting of memory and ultimately to a kernel
panic.
This is not a problem with 4k blocksize because
blk_queue_max_segment_size is set to PAGE_SIZE, always resulting in a
single iteration for the inner segment loop (bv.bv_len == blksize). The
incorrectly used 'off' value to increment dst is 0 and the correct
memory area is used.
In order to fix this for blksize < 4k, increment dst correctly using the
blksize and only do it at the end of the loop.
Fixes: 5e2b17e712cf ("s390/dasd: Add dynamic formatting support for ESE volumes")
Cc: stable@vger.kernel.org # v5.3+
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
Reviewed-by: Stefan Haberland <sth@linux.ibm.com>
Link: https://lore.kernel.org/r/20220505141733.1989450-4-sth@linux.ibm.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
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