dmabuf: fix NULL pointer dereference in dma_buf_release()

commit 19a508bd1ad8e444de86873bf2f2b2ab8edd6552 upstream.

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: <stable@vger.kernel.org> [5.7+]
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/391319/
Signed-off-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index 1ca609f66fdf889027a681c488ec0e425c3d6cdb..241c4b48d6099e3286cfa8b57ec8d1332ade52d6 100644 (file)
--- 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);