[PATCH 5.9 406/757] RDMA/ucma: Fix locking for ctx->events_reported

[Greg Kroah-Hartman]

From: Jason Gunthorpe <jgg@xxxxxxxxxx>

[ Upstream commit 98837c6c3d7285f6eca86480b6f7fac6880e27a8 ]

This value is locked under the file->mut, ensure it is held whenever
touching it.

The case in ucma_migrate_id() is a race, while in ucma_free_uctx() it is
already not possible for the write side to run, the movement is just for
clarity.

Fixes: 88314e4dda1e ("RDMA/cma: add support for rdma_migrate_id()")
Link: https://lore.kernel.org/r/20200818120526.702120-10-leon@xxxxxxxxxx
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/infiniband/core/ucma.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
index 1d184ea05eba1..75ccc31cf0b15 100644
--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -586,6 +586,7 @@ static int ucma_free_ctx(struct ucma_context *ctx)
 			list_move_tail(&uevent->list, &list);
 	}
 	list_del(&ctx->list);
+	events_reported = ctx->events_reported;
 	mutex_unlock(&ctx->file->mut);
 
 	list_for_each_entry_safe(uevent, tmp, &list, list) {
@@ -595,7 +596,6 @@ static int ucma_free_ctx(struct ucma_context *ctx)
 		kfree(uevent);
 	}
 
-	events_reported = ctx->events_reported;
 	mutex_destroy(&ctx->mutex);
 	kfree(ctx);
 	return events_reported;
@@ -1678,7 +1678,9 @@ static ssize_t ucma_migrate_id(struct ucma_file *new_file,
 
 	cur_file = ctx->file;
 	if (cur_file == new_file) {
+		mutex_lock(&cur_file->mut);
 		resp.events_reported = ctx->events_reported;
+		mutex_unlock(&cur_file->mut);
 		goto response;
 	}
 
-- 
2.25.1