[PATCH AUTOSEL 5.5 469/542] RDMA/core: Ensure that rdma_user_mmap_entry_remove() is a fence

[Sasha Levin]

From: Jason Gunthorpe <jgg@xxxxxxxxxxxx>

[ Upstream commit 6b3712c0246ca7b2b8fa05eab2362cf267410f7e ]

The set of entry->driver_removed is missing locking, protect it with
xa_lock() which is held by the only reader.

Otherwise readers may continue to see driver_removed = false after
rdma_user_mmap_entry_remove() returns and may continue to try and
establish new mmaps.

Fixes: 3411f9f01b76 ("RDMA/core: Create mmap database and cookie helper functions")
Link: https://lore.kernel.org/r/20200115202041.GA17199@xxxxxxxx
Reviewed-by: Gal Pressman <galpress@xxxxxxxxxx>
Acked-by: Michal Kalderon <michal.kalderon@xxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/infiniband/core/ib_core_uverbs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/infiniband/core/ib_core_uverbs.c b/drivers/infiniband/core/ib_core_uverbs.c
index b7cb59844ece4..b51bd7087a881 100644
--- a/drivers/infiniband/core/ib_core_uverbs.c
+++ b/drivers/infiniband/core/ib_core_uverbs.c
@@ -232,7 +232,9 @@ void rdma_user_mmap_entry_remove(struct rdma_user_mmap_entry *entry)
 	if (!entry)
 		return;
 
+	xa_lock(&entry->ucontext->mmap_xa);
 	entry->driver_removed = true;
+	xa_unlock(&entry->ucontext->mmap_xa);
 	kref_put(&entry->ref, rdma_user_mmap_entry_free);
 }
 EXPORT_SYMBOL(rdma_user_mmap_entry_remove);
-- 
2.20.1