linux-kernel - Re: Unused local variable load_addr in load_elf

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Message-ID: <20211207000150.whruf5uuzbxl274y@gmail.com>
Date:   Tue, 7 Dec 2021 09:01:50 +0900
From:   Akira Kawata <akirakawata1@...il.com>
To:     Lukas Bulwahn <lukas.bulwahn@...il.com>
Cc:     Alexey Dobriyan <adobriyan@...il.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Eric Biederman <ebiederm@...ssion.com>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernel-janitors <kernel-janitors@...r.kernel.org>
Subject: Re: Unused local variable load_addr in load_elf_binary()

On Mon, Dec 06, 2021 at 04:46:01PM +0100, Lukas Bulwahn wrote:
> Dear Akira-san,
> 
> With commit 0c9333606e30 ("fs/binfmt_elf: Fix AT_PHDR for unusual ELF
> files"), you have changed load_elf_binary() in ./fs/binfmt_elf.c in a
> way such that the local variable load_addr in load_elf_binary() is not
> used anymore.
> 
> I had a quick look at the code and I think the following refactoring
> would be good:
> 
> 1. Remove the definition of load_addr and its unneeded computation of load_addr
> 
> 2. Rename load_addr_set to first (or a similar name) to represent that
> this variable is not linked to the non-existing load_addr, but states
> that it captures the first iteration of the loop. Note that first has
> the inverse meaning of load_addr_set.
> 
> The issue was reported by make clang-analyzer:
> 
> ./fs/binfmt_elf.c:1167:5: warning: Value stored to 'load_addr' is
> never read [clang-analyzer-deadcode.DeadStores]
>                                 load_addr += load_bias;
>                                 ^            ~~~~~~~~~
> 
> 
> Best regards,
> 
> Lukas

Thank you for your comments. Should I send a new patch, or change
the existing patch in linux-next?

Akira