Re: [PATCH 2/2] [media] vb2: Fix error handling in '__vb2_buf_mem_alloc'

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Le 24/04/2017 à 16:23, Sakari Ailus a écrit :
Hi Christophe,

On Sun, Apr 23, 2017 at 11:40:30PM +0200, Christophe JAILLET wrote:
'call_ptr_memop' can return NULL, so we must test its return value with
'IS_ERR_OR_NULL'. Otherwise, the test 'if (mem_priv)' is meaningless.

Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
---
Note that error checking after 'call_ptr_memop' calls is not consistent
in this file. I guess that 'IS_ERR_OR_NULL' should be used everywhere
and that the corresponding error handling code should be tweaked just as
the code in this function.
---
  drivers/media/v4l2-core/videobuf2-core.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index c0175ea7e7ad..d1d3f5dd57b9 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -210,7 +210,7 @@ static int __vb2_buf_mem_alloc(struct vb2_buffer *vb)
  		mem_priv = call_ptr_memop(vb, alloc,
  				q->alloc_devs[plane] ? : q->dev,
  				q->dma_attrs, size, dma_dir, q->gfp_flags);
-		if (IS_ERR(mem_priv)) {
+		if (IS_ERR_OR_NULL(mem_priv)) {
  			if (mem_priv)
  				ret = PTR_ERR(mem_priv);
  			goto free;
If NULL will always equate -ENOMEM, shouldn't call_ptr_memop() be changed
instead to convert NULL to ERR_PTR(-ENOMEM)?

I agree with you, but in fact, I don't know if "NULL will always equate -ENOMEM"

The return value of 'call_ptr_memop' is likely the result of a function called via a function pointer. I don't know if this function can return NULL or not. I don't know the code enough to see if it would be safe and if this assertion is correct.

So the easiest for me is to just propose a fix to accept NULL.


*** Digging deeper ***

In 'videobuf2-core.h', there is:

/**
 * struct vb2_mem_ops - memory handling/memory allocator operations
* @alloc: allocate video memory and, optionally, allocator private data, * return ERR_PTR() on failure or a pointer to allocator private,
 *              per-buffer data on success; the returned private structure
* will then be passed as @buf_priv argument to other ops in this
 *              structure. Additional gfp_flags to use when allocating the
 *              are also passed to this operation. These flags are from the
 *              gfp_flags field of vb2_queue.

So the 'alloc' function should return an ERR_PTR in case of error.
'vb2_vmalloc_alloc', 'vb2_dc_alloc' and 'vb2_dma_sg_alloc' does. (confirmed by code inspection, based on the 'standard' list of alloc functions found in see https://lwn.net/Articles/447435/)

But what if a module implements its own set of functions and returns NULL in such a case?

Anyway, I will propose a patch that returns ERR_PTR(-ENOMEM) instead of NULL, but I won't be able to test it on my own.

Thanks,

CJ

--
To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Kernel Development]     [Kernel Announce]     [Kernel Newbies]     [Linux Networking Development]     [Share Photos]     [IDE]     [Security]     [Git]     [Netfilter]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Device Mapper]

  Powered by Linux