linux-kernel - Re: [RFC PATCH 2/2] binfmt_elf: Uninitialized variable

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Date:	Wed, 26 Sep 2012 16:25:02 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] binfmt_elf: Uninitialized variable

On Wed, 19 Sep 2012 15:45:01 +0100
Alan Cox <alan@...rguk.ukuu.org.uk> wrote:

> load_elf_interp has interp_map_addr carefully described as
> "uninitialized_var" and marked so as to avoid a warning. However
> if you trace the code it is passed into load_elf_interp and then
> this value is checked against NULL.
> 
> As this return value isn't used this is actually safe but it freaks
> various analysis tools that see un-initialized memory addresses
> being read before their value is ever defined.
> 
> Set it to NULL as a matter of programming good taste if nothing else
> 
> Signed-off-by: Alan Cox <alan@...ux.intel.com>
> ---
> 
>  fs/binfmt_elf.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index bf6d82b..5fb4801 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -880,7 +880,7 @@ static int load_elf_binary(struct linux_binprm *bprm, struct pt_regs *regs)
>  	}
>  
>  	if (elf_interpreter) {
> -		unsigned long uninitialized_var(interp_map_addr);
> +		unsigned long interp_map_addr = 0;
>  
>  		elf_entry = load_elf_interp(&loc->interp_elf_ex,
>  					    interpreter,

That looks right to me.
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