From: Jan Höppner <hoeppner@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxxxx # v5.3+
Signed-off-by: Jan Höppner <hoeppner@xxxxxxxxxxxxx>
Reviewed-by: Stefan Haberland <sth@xxxxxxxxxxxxx>
---
drivers/s390/block/dasd_eckd.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/drivers/s390/block/dasd_eckd.c b/drivers/s390/block/dasd_eckd.c
index 649eba51e048..e46461b4d8a7 100644
--- 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 dasd_ccw_req *cqr, struct irb *irb)
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++;
}
}
--
2.32.0
