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
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