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Date: Thu, 10 Dec 2020 14:51:23 -0300
From: Adhemerval Zanella <adhemerval.zanella@...aro.org>
To: Szabolcs Nagy <szabolcs.nagy@....com>, libc-alpha@...rceware.org
Cc: Mark Rutland <mark.rutland@....com>, kernel-hardening@...ts.openwall.com,
Catalin Marinas <catalin.marinas@....com>, linux-kernel@...r.kernel.org,
Jeremy Linton <jeremy.linton@....com>, Mark Brown <broonie@...nel.org>,
Topi Miettinen <toiwoton@...il.com>, Will Deacon <will@...nel.org>,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 1/6] aarch64: Fix missing BTI protection from
dependencies [BZ #26926]
On 27/11/2020 10:19, Szabolcs Nagy via Libc-alpha wrote:
> The _dl_open_check and _rtld_main_check hooks are not called on the
> dependencies of a loaded module, so BTI protection was missed on
> every module other than the main executable and directly dlopened
> libraries.
>
> The fix just iterates over dependencies to enable BTI.
>
> Fixes bug 26926.
LGTM, modulus the argument name change.
I also think it would be better to add a testcase, for both DT_NEEDED
and dlopen case.
> ---
> sysdeps/aarch64/dl-bti.c | 21 +++++++++++++++++----
> 1 file changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/sysdeps/aarch64/dl-bti.c b/sysdeps/aarch64/dl-bti.c
> index 196e462520..8f4728adce 100644
> --- a/sysdeps/aarch64/dl-bti.c
> +++ b/sysdeps/aarch64/dl-bti.c
> @@ -51,11 +51,24 @@ enable_bti (struct link_map *map, const char *program)
> return 0;
> }
>
> -/* Enable BTI for L if required. */
> +/* Enable BTI for MAP and its dependencies. */
>
> void
> -_dl_bti_check (struct link_map *l, const char *program)
> +_dl_bti_check (struct link_map *map, const char *program)
I don't see much gain changing the argument name.
> {
> - if (GLRO(dl_aarch64_cpu_features).bti && l->l_mach.bti)
> - enable_bti (l, program);
> + if (!GLRO(dl_aarch64_cpu_features).bti)
> + return;
> +
> + if (map->l_mach.bti)
> + enable_bti (map, program);
> +
> + unsigned int i = map->l_searchlist.r_nlist;
> + while (i-- > 0)
> + {
> + struct link_map *l = map->l_initfini[i];
> + if (l->l_init_called)
> + continue;
> + if (l->l_mach.bti)
> + enable_bti (l, program);
> + }
> }
>
Ok.
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