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Subject[PATCH 5.5 010/120] RDMA/core: Ensure that rdma_user_mmap_entry_remove() is a fence
Date
From: Jason Gunthorpe <jgg@mellanox.com>

commit 6b3712c0246ca7b2b8fa05eab2362cf267410f7e upstream.

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@ziepe.ca
Reviewed-by: Gal Pressman <galpress@amazon.com>
Acked-by: Michal Kalderon <michal.kalderon@marvell.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/infiniband/core/ib_core_uverbs.c | 2 ++
1 file changed, 2 insertions(+)

--- 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
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);

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