Re: [PATCH 1/3] binfmt_elf_fdpic: fix AUXV size calculation for ELF_HWCAP3 and ELF_HWCAP4

[Michal Koutný]

On Thu, Jan 08, 2026 at 05:07:46AM +0000, Andrei Vagin <avagin@xxxxxxxxxx> wrote:
> 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 ELF_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@xxxxxxxxxx>
> Cc: Max Filippov <jcmvbkbc@xxxxxxxxx>
> Fixes: 4e6e8c2b757f ("binfmt_elf: Wire up AT_HWCAP3 at AT_HWCAP4")
> Signed-off-by: Andrei Vagin <avagin@xxxxxxxxxx>
> ---
>  fs/binfmt_elf_fdpic.c  | 6 ++++++
>  include/linux/auxvec.h | 2 +-
>  2 files changed, 7 insertions(+), 1 deletion(-)

Good catch.
Reviewed-by: Michal Koutný <mkoutny@xxxxxxxx>

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