The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From f0abc761bbb9418876cc4d1ebc473e4ea6352e42 Mon Sep 17 00:00:00 2001
From: Leon Romanovsky leon@kernel.org Date: Thu, 23 Apr 2020 09:01:22 +0300 Subject: [PATCH] RDMA/core: Fix race between destroy and release FD object
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: 3832125624b7 ("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
diff --git a/drivers/infiniband/core/rdma_core.c b/drivers/infiniband/core/rdma_core.c index 2947f4f83561..177333d8bcda 100644 --- a/drivers/infiniband/core/rdma_core.c +++ b/drivers/infiniband/core/rdma_core.c @@ -678,7 +678,6 @@ void rdma_lookup_put_uobject(struct ib_uobject *uobj, enum rdma_lookup_mode mode) { assert_uverbs_usecnt(uobj, mode); - uobj->uapi_object->type_class->lookup_put(uobj, mode); /* * In order to unlock an object, either decrease its usecnt for * read access or zero it in case of exclusive access. See @@ -695,6 +694,7 @@ void rdma_lookup_put_uobject(struct ib_uobject *uobj, break; }
+ uobj->uapi_object->type_class->lookup_put(uobj, mode); /* Pairs with the kref obtained by type->lookup_get */ uverbs_uobject_put(uobj); }