Re: [RFC PATCH 2/2] binfmt_elf: Uninitialized variable

From: Andrew Morton
Date: Wed Sep 26 2012 - 19:24:56 EST


On Wed, 19 Sep 2012 15:45:01 +0100
Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
> ---
>
> 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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