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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Leon Romanovsky <leonro@mellanox.com>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.8 329/633] RDMA/ucma: Fix locking for ctx->events_reported
Date:   Tue, 27 Oct 2020 14:51:12 +0100
Message-Id: <20201027135538.113663554@linuxfoundation.org>
In-Reply-To: <20201027135522.655719020@linuxfoundation.org>
References: <20201027135522.655719020@linuxfoundation.org>
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From: Jason Gunthorpe <jgg@nvidia.com>

[ 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@kernel.org
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 d03dacaef7880..cf283b70bf877 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