On 3 May 2016 at 16:50, Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> wrote:
> On Mon, 02 May, at 09:25:00PM, Dan Carpenter wrote:
>> Hello Matt Fleming,
>>
>> The patch f0133f3c5b8b: "efi: Add 'capsule' update support" from Apr
>> 25, 2016, leads to the following static checker warning:
>>
>> drivers/firmware/efi/capsule.c:109 efi_capsule_supported()
>> warn: did you mean to pass the address of 'capsule'
>>
>> drivers/firmware/efi/capsule.c
>> 91 int efi_capsule_supported(efi_guid_t guid, u32 flags, size_t size, int *reset)
>> 92 {
>> 93 efi_capsule_header_t *capsule;
>> 94 efi_status_t status;
>> 95 u64 max_size;
>> 96 int rv = 0;
>> 97
>> 98 if (flags & ~EFI_CAPSULE_SUPPORTED_FLAG_MASK)
>> 99 return -EINVAL;
>> 100
>> 101 capsule = kmalloc(sizeof(*capsule), GFP_KERNEL);
>> 102 if (!capsule)
>> 103 return -ENOMEM;
>> 104
>> 105 capsule->headersize = capsule->imagesize = sizeof(*capsule);
>> 106 memcpy(&capsule->guid, &guid, sizeof(efi_guid_t));
>> 107 capsule->flags = flags;
>> 108
>> 109 status = efi.query_capsule_caps(&capsule, 1, &max_size, reset);
>> ^^^^^^^^
>> If we modify capsule inside this function call then at the end of the
>> function we aren't freeing the original pointer that we allocated.
>>
>> 110 if (status != EFI_SUCCESS) {
>> 111 rv = efi_status_to_err(status);
>> 112 goto out;
>> 113 }
>> 114
>> 115 if (size > max_size)
>> 116 rv = -ENOSPC;
>> 117 out:
>> 118 kfree(capsule);
>> 119 return rv;
>> 120 }
>
> We should be fine here, the firmware should not modify the argument
> that we pass since we're simply querying whether or not the capsule is
> supported.
>
> Is there a cleanup that you'd suggest making to silence the static
> checker warning?
Well, I suppose we could simply allocate the pointer array and the
single member statically, i.e.,
efi_capsule_header_t capsule1;
efi_capsule_header_t *capsule[] = { &capsule1 };
That way, we can get rid of the heap allocation entirely, and we take
the address of the array, i.e., without the &
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