dm: make sure to obey max_io_len_target_boundary

Commit 61697a6abd24 ("dm: eliminate 'split_discard_bios' flag from DM
target interface") incorrectly removed code from
__send_changing_extent_only() that is required to impose a per-target IO
boundary on IO that exceeds max_io_len_target_boundary().  Otherwise
"special" IO (e.g. DISCARD, WRITE SAME, WRITE ZEROES) can write beyond
where allowed.

Fix this by restoring the max_io_len_target_boundary() limit in
__send_changing_extent_only()

Fixes: 61697a6abd24 ("dm: eliminate 'split_discard_bios' flag from DM target interface")
Cc: stable@vger.kernel.org # 5.1+
Signed-off-by: Michael Lass <bevan@bi-co.net>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 1fb1333fefec..997385c1ca54 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1469,7 +1469,7 @@ static unsigned get_num_write_zeroes_bios(struct dm_target *ti)
 static int __send_changing_extent_only(struct clone_info *ci, struct dm_target *ti,
                                        unsigned num_bios)
 {
-        unsigned len = ci->sector_count;
+        unsigned len;
 
         /*
          * Even though the device advertised support for this type of
@@ -1480,6 +1480,8 @@ static int __send_changing_extent_only(struct clone_info *ci, struct dm_target *
         if (!num_bios)
                 return -EOPNOTSUPP;
 
+        len = min((sector_t)ci->sector_count, max_io_len_target_boundary(ci->sector, ti));
+
         __send_duplicate_bios(ci, ti, num_bios, &len);
 
         ci->sector += len;