From 19a508bd1ad8e444de86873bf2f2b2ab8edd6552 Mon Sep 17 00:00:00 2001 From: Charan Teja Reddy Date: Fri, 18 Sep 2020 16:02:31 +0530 Subject: [PATCH] dmabuf: fix NULL pointer dereference in dma_buf_release() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit NULL pointer dereference is observed while exporting the dmabuf but failed to allocate the 'struct file' which results into the dropping of the allocated dentry corresponding to this file in the dmabuf fs, which is ending up in dma_buf_release() and accessing the uninitialzed dentry->d_fsdata. Call stack on 5.4 is below: dma_buf_release+0x2c/0x254 drivers/dma-buf/dma-buf.c:88 __dentry_kill+0x294/0x31c fs/dcache.c:584 dentry_kill fs/dcache.c:673 [inline] dput+0x250/0x380 fs/dcache.c:859 path_put+0x24/0x40 fs/namei.c:485 alloc_file_pseudo+0x1a4/0x200 fs/file_table.c:235 dma_buf_getfile drivers/dma-buf/dma-buf.c:473 [inline] dma_buf_export+0x25c/0x3ec drivers/dma-buf/dma-buf.c:585 Fix this by checking for the valid pointer in the dentry->d_fsdata. Fixes: 4ab59c3c638c ("dma-buf: Move dma_buf_release() from fops to dentry_ops") Cc: [5.7+] Signed-off-by: Charan Teja Reddy Reviewed-by: Christian König Link: https://patchwork.freedesktop.org/patch/391319/ Signed-off-by: Christian König --- drivers/dma-buf/dma-buf.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c index 58564d82a3a2..844967f98866 100644 --- a/drivers/dma-buf/dma-buf.c +++ b/drivers/dma-buf/dma-buf.c @@ -59,6 +59,8 @@ static void dma_buf_release(struct dentry *dentry) struct dma_buf *dmabuf; dmabuf = dentry->d_fsdata; + if (unlikely(!dmabuf)) + return; BUG_ON(dmabuf->vmapping_counter);