commit f0abc761bb upstream.
The call to ->lookup_put() was too early and it caused an unlock of the
read/write protection of the uobject after the FD was put. This allows a
race:
CPU1 CPU2
rdma_lookup_put_uobject()
lookup_put_fd_uobject()
fput()
fput()
uverbs_uobject_fd_release()
WARN_ON(uverbs_try_lock_object(uobj,
UVERBS_LOOKUP_WRITE));
atomic_dec(usecnt)
Fix the code by changing the order, first unlock and call to
->lookup_put() after that.
Fixes: 3832125624 ("IB/core: Add support for idr types")
Link: https://lore.kernel.org/r/20200423060122.6182-1-leon@kernel.org
Suggested-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Leon Romanovsky
751e8b062a