Re: [PATCH] powerpc: Initialize local variable fdt to NULL in elf64_load()

[Michael Ellerman <mpe@ellerman.id.au>]

Daniel Axtens <dja@axtens.net> writes:
> Daniel Axtens <dja@axtens.net> writes:
>
>> Hi Lakshmi,
>>
>>> On 4/15/21 12:14 PM, Lakshmi Ramasubramanian wrote:
>>>
>>> Sorry - missed copying device-tree and powerpc mailing lists.
>>>
>>>> There are a few "goto out;" statements before the local variable "fdt"
>>>> is initialized through the call to of_kexec_alloc_and_setup_fdt() in
>>>> elf64_load(). This will result in an uninitialized "fdt" being passed
>>>> to kvfree() in this function if there is an error before the call to
>>>> of_kexec_alloc_and_setup_fdt().
>>>> 
>>>> Initialize the local variable "fdt" to NULL.
>>>>
>> I'm a huge fan of initialising local variables! But I'm struggling to
>> find the code path that will lead to an uninit fdt being returned...
>
> OK, so perhaps this was putting it too strongly. I have been bitten
> by uninitialised things enough in C that I may have taken a slightly
> overly-agressive view of fixing them in the source rather than the
> compiler. I do think compiler-level mitigations are better, and I take
> the point that we don't want to defeat compiler checking.
>
> (Does anyone - and by anyone I mean any large distro - compile with
> local variables inited by the compiler?)

This is where I say, "yes, Android" and you say "ugh no I meant a real
distro", and I say "well ...".

But yeah doesn't help us much.

cheers