IB/mlx5: Serialize access to the VMA list

IB/mlx5: Serialize access to the VMA list

commit ad9a3668a434faca1339789ed2f043d679199309 upstream.

User-space applications can do mmap and munmap directly at
any time.

Since the VMA list is not protected with a mutex, concurrent
accesses to the VMA list from the mmap and munmap can cause
data corruption. Add a mutex around the list.

Fixes: 7c2344c3bbf9 ("IB/mlx5: Implements disassociate_ucontext API")
Reviewed-by: Yishai Hadas <yishaih@mellanox.com>
Signed-off-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Leon Romanovsky <leon@kernel.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>