From bc5bc309db45a7ab218ce8259ba9bc7659be61ca Mon Sep 17 00:00:00 2001 From: Yafang Shao Date: Thu, 5 Oct 2023 08:41:23 +0000 Subject: [PATCH] bpf: Inherit system settings for CPU security mitigations Currently, there exists a system-wide setting related to CPU security mitigations, denoted as 'mitigations='. When set to 'mitigations=off', it deactivates all optional CPU mitigations. Therefore, if we implement a system-wide 'mitigations=off' setting, it should inherently bypass Spectre v1 and Spectre v4 in the BPF subsystem. Please note that there is also a more specific 'nospectre_v1' setting on x86 and ppc architectures, though it is not currently exported. For the time being, let's disregard more fine-grained options. This idea emerged during our discussion about potential Spectre v1 attacks with Luis [0]. [0] https://lore.kernel.org/bpf/b4fc15f7-b204-767e-ebb9-fdb4233961fb@iogearbox.net Signed-off-by: Yafang Shao Signed-off-by: Daniel Borkmann Acked-by: Stanislav Fomichev Acked-by: Song Liu Acked-by: KP Singh Cc: Luis Gerhorst Link: https://lore.kernel.org/bpf/20231005084123.1338-1-laoar.shao@gmail.com --- include/linux/bpf.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index a82efd34b741..61bde4520f5c 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -2164,12 +2164,12 @@ static inline bool bpf_allow_uninit_stack(void) static inline bool bpf_bypass_spec_v1(void) { - return perfmon_capable(); + return perfmon_capable() || cpu_mitigations_off(); } static inline bool bpf_bypass_spec_v4(void) { - return perfmon_capable(); + return perfmon_capable() || cpu_mitigations_off(); } int bpf_map_new_fd(struct bpf_map *map, int flags);