linux-kernel - Re: [PATCH] binfmt_elf_fdpic: fix AUXV size calculation when ELF

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Message-ID: <aa4af643-47d3-4c26-8537-d86c1f73af68@westnet.com.au>
Date: Mon, 26 Aug 2024 17:00:13 +1000
From: Greg Ungerer <gregungerer@...tnet.com.au>
To: Max Filippov <jcmvbkbc@...il.com>, linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
 Alexander Viro <viro@...iv.linux.org.uk>,
 Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
 Eric Biederman <ebiederm@...ssion.com>, Kees Cook <kees@...nel.org>,
 stable@...r.kernel.org
Subject: Re: [PATCH] binfmt_elf_fdpic: fix AUXV size calculation when
 ELF_HWCAP2 is defined

Hi Max,

On 26/8/24 13:27, Max Filippov wrote:
> create_elf_fdpic_tables() does not correctly account the space for the
> AUX vector when an architecture has ELF_HWCAP2 defined. Prior to the
> commit 10e29251be0e ("binfmt_elf_fdpic: fix /proc/<pid>/auxv") it
> resulted in the last entry of the AUX vector being set to zero, but with
> that change it results in a kernel BUG.
> 
> Fix that by adding one to the number of AUXV entries (nitems) when
> ELF_HWCAP2 is defined.
> 
> Fixes: 10e29251be0e ("binfmt_elf_fdpic: fix /proc/<pid>/auxv")
> Cc: stable@...r.kernel.org
> Reported-by: Greg Ungerer <gregungerer@...tnet.com.au>

Feel free to use my gerg@...nel.org email for this.


> Closes: https://lore.kernel.org/lkml/5b51975f-6d0b-413c-8b38-39a6a45e8821@westnet.com.au/
> Signed-off-by: Max Filippov <jcmvbkbc@...il.com>

Certainly fixes it for all my failing test cases, so:

Tested-by: Greg Ungerer <gerg@...nel.org>

Thanks for looking into it and the fix.

Regards
Greg


> ---
>   fs/binfmt_elf_fdpic.c | 3 +++
>   1 file changed, 3 insertions(+)
> 
> diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
> index c11289e1301b..a5cb45cb30c8 100644
> --- a/fs/binfmt_elf_fdpic.c
> +++ b/fs/binfmt_elf_fdpic.c
> @@ -594,6 +594,9 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
>   
>   	if (bprm->have_execfd)
>   		nitems++;
> +#ifdef ELF_HWCAP2
> +	nitems++;
> +#endif
>   
>   	csp = sp;
>   	sp -= nitems * 2 * sizeof(unsigned long);