[PATCH 4.15 22/72] RDMA/ucma: Fix use-after-free access in ucma_close

[Greg Kroah-Hartman]

4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Leon Romanovsky <leonro@xxxxxxxxxxxx>

commit ed65a4dc22083e73bac599ded6a262318cad7baf upstream.

The error in ucma_create_id() left ctx in the list of contexts belong
to ucma file descriptor. The attempt to close this file descriptor causes
to use-after-free accesses while iterating over such list.

Fixes: 75216638572f ("RDMA/cma: Export rdma cm interface to userspace")
Reported-by: <syzbot+dcfd344365a56fbebd0f@xxxxxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
Reviewed-by: Sean Hefty <sean.hefty@xxxxxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/infiniband/core/ucma.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -497,6 +497,9 @@ err1:
 	mutex_lock(&mut);
 	idr_remove(&ctx_idr, ctx->id);
 	mutex_unlock(&mut);
+	mutex_lock(&file->mut);
+	list_del(&ctx->list);
+	mutex_unlock(&file->mut);
 	kfree(ctx);
 	return ret;
 }