Re: [PATCH] dma-buf: propagate errors from dma_buf_describe() on debugfs read

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Jun 17, 2016 at 08:57:03PM +0200, Mathias Krause wrote:
> The callback function dma_buf_describe() returns an int not void so the
> function pointer cast in dma_buf_show() is wrong. dma_buf_describe() can
> also fail when acquiring the mutex gets interrupted so always returning
> 0 in dma_buf_show() is wrong, too.
> 
> Fix both issues by casting the function pointer to the correct type and
> propagate its return value.
> 
> This type mismatch was caught by the PaX RAP plugin.
> 
> Signed-off-by: Mathias Krause <minipli@googlemail.com>
> Cc: Sumit Semwal <sumit.semwal@linaro.org>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Cc: PaX Team <pageexec@freemail.hu>
> ---
>  drivers/dma-buf/dma-buf.c |    5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index 6355ab38d630..0f2a4592fdd2 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -881,10 +881,9 @@ static int dma_buf_describe(struct seq_file *s)
>  
>  static int dma_buf_show(struct seq_file *s, void *unused)
>  {
> -	void (*func)(struct seq_file *) = s->private;
> +	int (*func)(struct seq_file *) = s->private;
>  
> -	func(s);
> -	return 0;
> +	return func(s);

Probably even better to just nuke that indirection. Set this pointer to
NULL and inline dma_buf_describe into dma_buf_show.
-Daniel

>  }
>  
>  static int dma_buf_debug_open(struct inode *inode, struct file *file)
> -- 
> 1.7.10.4
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch