On 12/24/21 3:03 AM, Jiasheng Jiang wrote:

As the possible alloc failure of devm_kcalloc, it could return null pointer. To prevent the dereference of the null pointer, it should be checked.

I think this is a good change, but I would like you to improve the description, and fix some different bugs introduced by your change.

What you are specifically doing is checking for a null return from devm_kcalloc() in gb_generate_enum_strings(), and are returning the NULL pointer if that occurs. That means you need to update all the callers of gb_generate_enum_strings() to also handle a possible null return value.

The fix does a good thing, and your description is correct about what you are fixing. But it should supply more complete context for the change.

More below.

Fixes: e65579e335da ("greybus: audio: topology: Enable enumerated control support") Signed-off-by: Jiasheng Jiang jiasheng@iscas.ac.cn

---

drivers/staging/greybus/audio_topology.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)

diff --git a/drivers/staging/greybus/audio_topology.c b/drivers/staging/greybus/audio_topology.c index 1fc7727ab7be..e9f47a1f0d28 100644 --- a/drivers/staging/greybus/audio_topology.c +++ b/drivers/staging/greybus/audio_topology.c @@ -146,7 +146,11 @@ static const char **gb_generate_enum_strings(struct gbaudio_module_info *gb, __u8 *data; items = le32_to_cpu(gbenum->items);

• strings = devm_kcalloc(gb->dev, items, sizeof(char *), GFP_KERNEL);
• if (!strings)

• return NULL;
  

• data = gbenum->names;

for (i = 0; i < items; i++) { @@ -654,7 +658,10 @@ static int gbaudio_tplg_create_enum_kctl(struct gbaudio_module_info *gb, /* since count=1, and reg is dummy */ gbe->items = le32_to_cpu(gb_enum->items);

• gbe->texts = gb_generate_enum_strings(gb, gb_enum);
• if (!gbe->texts)

• return -ENOMEM;
  

/* debug enum info */ dev_dbg(gb->dev, "Max:%d, name_length:%d\n", gbe->items, @@ -861,7 +868,10 @@ static int gbaudio_tplg_create_enum_ctl(struct gbaudio_module_info *gb, /* since count=1, and reg is dummy */ gbe->items = le32_to_cpu(gb_enum->items);

• gbe->texts = gb_generate_enum_strings(gb, gb_enum);
• if (!gbe->texts)

• return -ENOMEM;
  

/* debug enum info */ dev_dbg(gb->dev, "Max:%d, name_length:%d\n", gbe->items, @@ -1032,8 +1042,12 @@ static int gbaudio_tplg_create_widget(struct gbaudio_module_info *module, csize += offsetof(struct gb_audio_ctl_elem_info, value); csize += offsetof(struct gb_audio_enumerated, names); csize += le16_to_cpu(gbenum->names_length);

• control->texts = (const char * const *)
  	gb_generate_enum_strings(module, gbenum);
  

• 	if (!control->texts)
  

• 		return -ENOMEM;
  

You can't simply return here. If you look a bit above this, where the call to allocate a control structure is done, you see that a NULL return there jumps to the "error" label, so any already allocated and initialized control widgets get cleaned up before returning.

	control->items = le32_to_cpu(gbenum->items);
} else {
	csize = sizeof(struct gb_audio_control);

@@ -1181,8 +1195,12 @@ static int gbaudio_tplg_process_kcontrols(struct gbaudio_module_info *module, csize += offsetof(struct gb_audio_ctl_elem_info, value); csize += offsetof(struct gb_audio_enumerated, names); csize += le16_to_cpu(gbenum->names_length);

• control->texts = (const char * const *)
  	gb_generate_enum_strings(module, gbenum);
  

• 	if (!control->texts)
  

• 		return -ENOMEM;
  

You have basically the same issue here. You can't just return, you must do some cleanup too.

-Alex

	control->items = le32_to_cpu(gbenum->items);
} else {
	csize = sizeof(struct gb_audio_control);