From mboxrd@z Thu Jan 1 00:00:00 1970 From: Cong Wang Subject: [PATCH] infiniband: fix a possible use-after-free bug Date: Fri, 1 Jun 2018 11:31:44 -0700 Message-ID: <20180601183144.17374-1-xiyou.wangcong@gmail.com> Return-path: Sender: linux-kernel-owner@vger.kernel.org To: linux-kernel@vger.kernel.org Cc: noamr@beyondsecurity.com, Cong Wang , Sean Hefty , Doug Ledford , Jason Gunthorpe , linux-rdma@vger.kernel.org List-Id: linux-rdma@vger.kernel.org ucma_process_join() will free the new allocated "mc" struct, if there is any error after that, especially the copy_to_user(). But in parallel, ucma_leave_multicast() could find this "mc" through idr_find() before ucma_process_join() frees it, since it is already published. So "mc" could be used in ucma_leave_multicast() after it is been allocated and freed in ucma_process_join(), since we don't refcnt it. Fix this by separating "publish" from ID allocation, so that we can get an ID first and publish it later after copy_to_user(). Fixes c8f6a362bf3e ("RDMA/cma: Add multicast communication support") Reported-by: Noam Rathaus Cc: Sean Hefty Cc: Doug Ledford Cc: Jason Gunthorpe Cc: linux-rdma@vger.kernel.org Signed-off-by: Cong Wang --- drivers/infiniband/core/ucma.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/infiniband/core/ucma.c b/drivers/infiniband/core/ucma.c index eab43b17e9cf..ec8fb289621f 100644 --- a/drivers/infiniband/core/ucma.c +++ b/drivers/infiniband/core/ucma.c @@ -235,7 +235,7 @@ static struct ucma_multicast* ucma_alloc_multicast(struct ucma_context *ctx) return NULL; mutex_lock(&mut); - mc->id = idr_alloc(&multicast_idr, mc, 0, 0, GFP_KERNEL); + mc->id = idr_alloc(&multicast_idr, NULL, 0, 0, GFP_KERNEL); mutex_unlock(&mut); if (mc->id < 0) goto error; @@ -1421,6 +1421,10 @@ static ssize_t ucma_process_join(struct ucma_file *file, goto err3; } + mutex_lock(&mut); + idr_replace(&multicast_idr, mc, mc->id); + mutex_unlock(&mut); + mutex_unlock(&file->mut); ucma_put_ctx(ctx); return 0; -- 2.13.0