Re: [PATCH 1/4] binfmt_elf_fdpic: fix AUXV size calculation for ELF_HWCAP3 and ELF_HWCAP4

[Alexander Mikhalitsyn <alexander@mihalicyn.com>]

Am Mo., 9. Feb. 2026 um 20:06 Uhr schrieb Andrei Vagin <avagin@google.com>:
>
> Commit 4e6e8c2b757f ("binfmt_elf: Wire up AT_HWCAP3 at AT_HWCAP4") added
> support for AT_HWCAP3 and AT_HWCAP4, but it missed updating the AUX
> vector size calculation in create_elf_fdpic_tables() and
> AT_VECTOR_SIZE_BASE in include/linux/auxvec.h.
>
> Similar to the fix for AT_HWCAP2 in commit c6a09e342f8e ("binfmt_elf_fdpic:
> fix AUXV size calculation when ELF_HWCAP2 is defined"), this omission
> leads to a mismatch between the reserved space and the actual number of
> AUX entries, eventually triggering a kernel BUG_ON(csp != sp).
>
> Fix this by incrementing nitems when ELF_HWCAP3 or ELF_HWCAP4 are
> defined and updating AT_VECTOR_SIZE_BASE.
>
> Cc: Mark Brown <broonie@kernel.org>
> Cc: Max Filippov <jcmvbkbc@gmail.com>
> Reviewed-by: Michal Koutný <mkoutny@suse.com>
> Reviewed-by: Mark Brown <broonie@kernel.org>

Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@futurfusion.io>

> Fixes: 4e6e8c2b757f ("binfmt_elf: Wire up AT_HWCAP3 at AT_HWCAP4")
> Signed-off-by: Andrei Vagin <avagin@google.com>
> ---
>  fs/binfmt_elf_fdpic.c  | 6 ++++++
>  include/linux/auxvec.h | 2 +-
>  2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
> index 48fd2de3bca0..a3d4e6973b29 100644
> --- a/fs/binfmt_elf_fdpic.c
> +++ b/fs/binfmt_elf_fdpic.c
> @@ -595,6 +595,12 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
>  #ifdef ELF_HWCAP2
>         nitems++;
>  #endif
> +#ifdef ELF_HWCAP3
> +       nitems++;
> +#endif
> +#ifdef ELF_HWCAP4
> +       nitems++;
> +#endif
>
>         csp = sp;
>         sp -= nitems * 2 * sizeof(unsigned long);
> diff --git a/include/linux/auxvec.h b/include/linux/auxvec.h
> index 407f7005e6d6..8bcb9b726262 100644
> --- a/include/linux/auxvec.h
> +++ b/include/linux/auxvec.h
> @@ -4,6 +4,6 @@
>
>  #include <uapi/linux/auxvec.h>
>
> -#define AT_VECTOR_SIZE_BASE 22 /* NEW_AUX_ENT entries in auxiliary table */
> +#define AT_VECTOR_SIZE_BASE 24 /* NEW_AUX_ENT entries in auxiliary table */
>    /* number of "#define AT_.*" above, minus {AT_NULL, AT_IGNORE, AT_NOTELF} */
>  #endif /* _LINUX_AUXVEC_H */
> --
> 2.53.0.239.g8d8fc8a987-goog
>