[ Upstream commit 25e70c6162f207828dd405b432d8f2a98dbf7082 ] This should be applied to most URSAN bugs found recently by syzbot, by guarding the dbMount. As syzbot feeding rubbish into the bmap descriptor. Signed-off-by: Hoi Pok Wu <wuhoipok@gmail.com> Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com> Signed-off-by: Sasha Levin <sashal@kernel.org>