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

2018-06-14 Thread Ian Abbott 

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

Hi,

I reported this bug since more than 90% callsites of vmap are
well handled in kernel. The caller function __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.

Best,
Zhouyang


__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 >:


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.

regards,
dan carpenter






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

2018-06-12 Thread Dan Carpenter 
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.

regards,
dan carpenter


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

2018-06-11 Thread Zhouyang Jia 
When vmap fails, the lack of error-handling code may
cause unexpected results.

This patch adds error-handling code after calling vmap.

Signed-off-by: Zhouyang Jia 
---
 drivers/staging/comedi/comedi_buf.c | 5 -
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/comedi/comedi_buf.c 
b/drivers/staging/comedi/comedi_buf.c
index f693c2c..5e48693 100644
--- a/drivers/staging/comedi/comedi_buf.c
+++ b/drivers/staging/comedi/comedi_buf.c
@@ -132,9 +132,12 @@ static void __comedi_buf_alloc(struct comedi_device *dev,
spin_unlock_irqrestore(>spin_lock, flags);
 
/* vmap the prealloc_buf if all the pages were allocated */
-   if (i == n_pages)
+   if (i == n_pages) {
async->prealloc_buf = vmap(pages, n_pages, VM_MAP,
   COMEDI_PAGE_PROTECTION);
+   if (!async->prealloc_buf)
+   dev_err(dev->class_dev, "failed to vmap pages\n");
+   }
 
vfree(pages);
 }
-- 
2.7.4

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