On 3 May 2016 at 16:50, Matt Fleming [off-list ref] wrote:

On Mon, 02 May, at 09:25:00PM, Dan Carpenter wrote:

quoted

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 &