IB/core: Fix deadlock on uverbs modify_qp error flow
The deadlock occurs in __uverbs_modify_qp: we take a lock (idr_read_qp)
and in case of failure in ib_resolve_eth_l2_attrs we don't release
it (put_qp_read). Fix that.
Fixes: ed4c54e5b4ba ("IB/core: Resolve Ethernet L2 addresses when modifying QP") Signed-off-by: Moshe Lazer <moshel@mellanox.com> Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com> Signed-off-by: Roland Dreier <roland@purestorage.com>