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Date: Thu, 23 Jan 2020 07:24:37 -0800 From: KP Singh <kpsingh@...omium.org> To: linux-kernel@...r.kernel.org, bpf@...r.kernel.org, linux-security-module@...r.kernel.org Cc: Brendan Jackman <jackmanb@...gle.com>, Florent Revest <revest@...gle.com>, Thomas Garnier <thgarnie@...gle.com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, James Morris <jmorris@...ei.org>, Kees Cook <keescook@...omium.org>, Thomas Garnier <thgarnie@...omium.org>, Michael Halcrow <mhalcrow@...gle.com>, Paul Turner <pjt@...gle.com>, Brendan Gregg <brendan.d.gregg@...il.com>, Jann Horn <jannh@...gle.com>, Matthew Garrett <mjg59@...gle.com>, Christian Brauner <christian@...uner.io>, Mickaël Salaün <mic@...ikod.net>, Florent Revest <revest@...omium.org>, Brendan Jackman <jackmanb@...omium.org>, Martin KaFai Lau <kafai@...com>, Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, "Serge E. Hallyn" <serge@...lyn.com>, Mauro Carvalho Chehab <mchehab+samsung@...nel.org>, "David S. Miller" <davem@...emloft.net>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Nicolas Ferre <nicolas.ferre@...rochip.com>, Stanislav Fomichev <sdf@...gle.com>, Quentin Monnet <quentin.monnet@...ronome.com>, Andrey Ignatov <rdna@...com>, Joe Stringer <joe@...d.net.nz> Subject: [PATCH bpf-next v3 07/10] bpf: lsm: Make the allocated callback RO+X From: KP Singh <kpsingh@...gle.com> This patch is not needed after arch_bpf_prepare_trampoline moves to using text_poke. The two IPI TLB flushes can be further optimized if a new API to handle W^X in the kernel emerges as an outcome of: https://lore.kernel.org/bpf/20200103234725.22846-1-kpsingh@chromium.org/ Signed-off-by: KP Singh <kpsingh@...gle.com> Reviewed-by: Brendan Jackman <jackmanb@...gle.com> Reviewed-by: Florent Revest <revest@...gle.com> Reviewed-by: Thomas Garnier <thgarnie@...gle.com> --- security/bpf/hooks.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/security/bpf/hooks.c b/security/bpf/hooks.c index f1d4fdcdb20e..beeeb8c1f9c2 100644 --- a/security/bpf/hooks.c +++ b/security/bpf/hooks.c @@ -190,6 +190,15 @@ static struct bpf_lsm_hook *bpf_lsm_hook_alloc(struct bpf_lsm_list *list, goto error; } + /* First make the page read-only, and only then make it executable to + * prevent it from being W+X in between. + */ + set_memory_ro((unsigned long)image, 1); + /* More checks can be done here to ensure that nothing was changed + * between arch_prepare_bpf_trampoline and set_memory_ro. + */ + set_memory_x((unsigned long)image, 1); + hook = kzalloc(sizeof(struct bpf_lsm_hook), GFP_KERNEL); if (!hook) { ret = -ENOMEM; -- 2.20.1
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