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@xxxxxxxxxxx>
---
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);
