Re: [PATCH] staging: comedi: add error handling for vmap

From: Ian Abbott
Date: Thu Jun 14 2018 - 05:58:49 EST

On 14/06/18 08:57, Zhouyang Jia wrote:

I reported this bug since more than 90% callsites of vmap are
well handled in kernel. The caller functionÂ__comedi_buf_alloc
has no return value, so I don't know how the error is handled in
its caller.

I believe there would be a better error handling method, but I
have limited domain knowledge, so I'm sorry I can't help here.

Thanks for your kind reply.


__comedi_buf_alloc is just a helper function factored out of, and called by comedi_buf_alloc. __comedi_buf_alloc does not clean up after itself on error because it expects comedi_buf_alloc to detect the error and call __comedi_buf_free to clean up any partially allocated mess:

__comedi_buf_alloc(dev, s, n_pages);
if (!async->prealloc_buf) {
* [This is not the actual comment in the code!]
* Error occured in __comedi_buf_alloc().
* Buffer may be partially allocated.
* Call __comedi_buf_free() to clean it up.
__comedi_buf_free(dev, s);
return -ENOMEM;

2018-06-12 19:50 GMT+08:00 Dan Carpenter <dan.carpenter@xxxxxxxxxx <mailto:dan.carpenter@xxxxxxxxxx>>:

On Tue, Jun 12, 2018 at 11:25:35AM +0800, Zhouyang Jia wrote:
> When vmap fails, the lack of error-handling code may
> cause unexpected results.
> > This patch adds error-handling code after calling vmap.
Again, this is not error handling, this is just an error message. This
error condition is handled in the caller.

dan carpenter

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