On Fri, Oct 29, 2021 at 12:43:54PM -0700, Pawan Gupta wrote: > 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> FWIW: Acked-by: Mark Rutland <mark.rutland@xxxxxxx> Mark. > --- > 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 >
