From: Jan Höppner hoeppner@linux.ibm.com
commit cd68c48ea15c85f1577a442dc4c285e112ff1b37 upstream.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/s390/block/dasd_eckd.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-)
--- a/drivers/s390/block/dasd_eckd.c +++ b/drivers/s390/block/dasd_eckd.c @@ -3285,12 +3285,11 @@ static int dasd_eckd_ese_read(struct das cqr->proc_bytes = blk_count * blksize; return 0; } - if (dst && !skip_block) { - dst += off; + if (dst && !skip_block) memset(dst, 0, blksize); - } else { + else skip_block--; - } + dst += blksize; blk_count++; } }