From 0b17ac3f080da021b759043ae9ab8dd8bbc5e852 Mon Sep 17 00:00:00 2001
From: Leon Romanovsky <leonro@mellanox.com>
Date: Mon, 19 Mar 2018 14:20:15 +0200
Subject: [PATCH] RDMA/ucma: Fix use-after-free access in ucma_close

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@syzkaller.appspotmail.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Reviewed-by: Sean Hefty <sean.hefty@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/infiniband/core/ucma.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c
index 1c0f3f7808123b..05872634839282 100644
--- a/drivers/infiniband/core/ucma.c
+++ b/drivers/infiniband/core/ucma.c
@@ -497,6 +497,9 @@ static ssize_t ucma_create_id(struct ucma_file *file, const char __user *inbuf,
 	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;
 }