jfs: check if leafidx greater than num leaves per dmap tree

[ Upstream commit d64ff0d2306713ff084d4b09f84ed1a8c75ecc32 ]

syzbot report a out of bounds in dbSplit, it because dmt_leafidx greater
than num leaves per dmap tree, add a checking for dmt_leafidx in dbFindLeaf.

Shaggy:
Modified sanity check to apply to control pages as well as leaf pages.

Reported-and-tested-by:  <syzbot+dca05492eff41f604890@syzkaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=dca05492eff41f604890


Signed-off-by: Edward Adam Davis <eadavis@qq.com>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
(cherry picked from commit d76b9a4c283c7535ae7c7c9b14984e75402951e1)
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Harshit Mogalapalli <harshit.m.mogalapalli@oracle.com>