Re: [PATCH] binfmt_elf_fdpic: fix AUXV size calculation when ELF_HWCAP2 is defined

[Greg Ungerer <gregungerer@xxxxxxxxxxxxxx>]

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@xxxxxxxxxxxxxxx
> Reported-by: Greg Ungerer <gregungerer@xxxxxxxxxxxxxx>

Feel free to use my gerg@xxxxxxxxxx email for this.


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

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

Tested-by: Greg Ungerer <gerg@xxxxxxxxxx>

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);