linux-kernel - Re: [PATCH 1/4] binfmt_elf_fdpic: fix AUXV size calculation for ELF_HWCAP3 and ELF

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Message-ID: <CAJqdLrpjW2TLKkhbQ-pG4tP=TFiJDcLGtGDrBqcxJnD+e1dZ9w@mail.gmail.com>
Date: Tue, 10 Feb 2026 20:59:07 +0100
From: Alexander Mikhalitsyn <alexander@...alicyn.com>
To: Andrei Vagin <avagin@...gle.com>
Cc: Kees Cook <kees@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Cyrill Gorcunov <gorcunov@...il.com>, Mike Rapoport <rppt@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, criu@...ts.linux.dev, 
	Chen Ridong <chenridong@...wei.com>, Christian Brauner <brauner@...nel.org>, 
	David Hildenbrand <david@...nel.org>, Eric Biederman <ebiederm@...ssion.com>, 
	Lorenzo Stoakes <lorenzo.stoakes@...cle.com>, Michal Koutny <mkoutny@...e.com>, 
	Mark Brown <broonie@...nel.org>, Max Filippov <jcmvbkbc@...il.com>
Subject: Re: [PATCH 1/4] binfmt_elf_fdpic: fix AUXV size calculation for
 ELF_HWCAP3 and ELF_HWCAP4

Am Mo., 9. Feb. 2026 um 20:06 Uhr schrieb Andrei Vagin <avagin@...gle.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@...nel.org>
> Cc: Max Filippov <jcmvbkbc@...il.com>
> Reviewed-by: Michal Koutný <mkoutny@...e.com>
> Reviewed-by: Mark Brown <broonie@...nel.org>

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

> Fixes: 4e6e8c2b757f ("binfmt_elf: Wire up AT_HWCAP3 at AT_HWCAP4")
> Signed-off-by: Andrei Vagin <avagin@...gle.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
>