Disabling unprivileged BPF would help prevent unprivileged users from creating the conditions required for potential speculative execution side-channel attacks on affected hardware. A deep dive on such attacks and mitigation is available here [1]. Sync with what many distros are currently applying, disable unprivileged BPF by default. An admin can enable this at runtime, if necessary. [1] https://ebpf.io/summit-2021-slides/eBPF_Summit_2021-Keynote-Daniel_Borkmann-BPF_and_Spectre.pdf Signed-off-by: Pawan Gupta <pawan.kumar.gupta@xxxxxxxxxxxxxxx> --- v3: - Drop the conditional default for CONFIG_BPF_UNPRIV_DEFAULT_OFF until we have an arch generic way to determine arch-common spectre type bugs. [Mark Rutland, Daniel Borkmann]. - Also drop the patch to Generalize ARM's CONFIG_CPU_SPECTRE. - Minor changes to commit message. v2: https://lore.kernel.org/lkml/cover.1635383031.git.pawan.kumar.gupta@xxxxxxxxxxxxxxx/ - Generalize ARM's CONFIG_CPU_SPECTRE to be available for all architectures. - Make CONFIG_BPF_UNPRIV_DEFAULT_OFF depend on CONFIG_CPU_SPECTRE. - Updated commit message to reflect the dependency on CONFIG_CPU_SPECTRE. - Add reference to BPF spectre presentation in commit message. v1: https://lore.kernel.org/all/d37b01e70e65dced2659561ed5bc4b2ed1a50711.1635367330.git.pawan.kumar.gupta@xxxxxxxxxxxxxxx/ kernel/bpf/Kconfig | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig index a82d6de86522..73d446294455 100644 --- a/kernel/bpf/Kconfig +++ b/kernel/bpf/Kconfig @@ -64,6 +64,7 @@ config BPF_JIT_DEFAULT_ON config BPF_UNPRIV_DEFAULT_OFF bool "Disable unprivileged BPF by default" + default y depends on BPF_SYSCALL help Disables unprivileged BPF by default by setting the corresponding @@ -72,6 +73,10 @@ config BPF_UNPRIV_DEFAULT_OFF disable it by setting it to 1 (from which no other transition to 0 is possible anymore). + Unprivileged BPF can be used to exploit potential speculative + execution side-channel vulnerabilities on affected hardware. If you + are concerned about it, answer Y. + source "kernel/bpf/preload/Kconfig" config BPF_LSM -- 2.31.1
