| Message ID | 882f5c31f48bac75ebaede2a0ec321ec67128229.1635383031.git.pawan.kumar.gupta@linux.intel.com (mailing list archive) |
|---|---|
| State | Changes Requested |
| Delegated to: | BPF |
| Headers | show |
| Series | Unprivileged BPF default | expand |
| Context | Check | Description |
|---|---|---|
| bpf/vmtest-bpf-next | success | VM_Test |
| bpf/vmtest-bpf-next-PR | success | PR summary |
| bpf/vmtest-bpf | success | VM_Test |
| bpf/vmtest-bpf-PR | success | PR summary |
On Wed, Oct 27, 2021 at 06:35:44PM -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]. > > If an architecture selects CONFIG_CPU_SPECTRE, disable unprivileged BPF > by default. An admin can enable this at runtime, if necessary. > > Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> > > [1] https://ebpf.io/summit-2021-slides/eBPF_Summit_2021-Keynote-Daniel_Borkmann-BPF_and_Spectre.pdf This should go above the signed-off-by line, in the changelog text, not below it, otherwise our tools get confused when trying to apply it. thanks, greg k-h
On Wed, Oct 27, 2021 at 06:35:44PM -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]. > > If an architecture selects CONFIG_CPU_SPECTRE, disable unprivileged BPF > by default. An admin can enable this at runtime, if necessary. > > Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> > > [1] https://ebpf.io/summit-2021-slides/eBPF_Summit_2021-Keynote-Daniel_Borkmann-BPF_and_Spectre.pdf > --- > kernel/bpf/Kconfig | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig > index a82d6de86522..510a5a73f9a2 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 if CPU_SPECTRE Why can't this just be "default y"? This series makes that the case on x86, and if SW is going to have to deal with that we may as well do that everywhere, and say that on all architectures we leave it to the sysadmin or kernel builder to optin to permitting unprivileged BPF. If we can change the default for x86 I see no reason we can't change this globally, and we avoid tying this to CPU_SPECTRE specifically. Thanks, Mark. > 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 >
On Thu, Oct 28, 2021 at 02:57:51PM +0100, Mark Rutland wrote: > On Wed, Oct 27, 2021 at 06:35:44PM -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]. > > > > If an architecture selects CONFIG_CPU_SPECTRE, disable unprivileged BPF > > by default. An admin can enable this at runtime, if necessary. > > > > Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> > > > > [1] https://ebpf.io/summit-2021-slides/eBPF_Summit_2021-Keynote-Daniel_Borkmann-BPF_and_Spectre.pdf > > --- > > kernel/bpf/Kconfig | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig > > index a82d6de86522..510a5a73f9a2 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 if CPU_SPECTRE > > Why can't this just be "default y"? Because not all arches are broken. > This series makes that the case on x86, and if SW is going to have to > deal with that we may as well do that everywhere, and say that on all > architectures we leave it to the sysadmin or kernel builder to optin to > permitting unprivileged BPF. > > If we can change the default for x86 I see no reason we can't change > this globally, and we avoid tying this to CPU_SPECTRE specifically. No, this is a spectre-like issue only, if you have hardware that does not have these types of issues, why wouldn't this be ok to be disabled? thanks, greg k-h
On 28.10.2021 07:34, Greg KH wrote: >On Wed, Oct 27, 2021 at 06:35:44PM -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]. >> >> If an architecture selects CONFIG_CPU_SPECTRE, disable unprivileged BPF >> by default. An admin can enable this at runtime, if necessary. >> >> Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> >> >> [1] https://ebpf.io/summit-2021-slides/eBPF_Summit_2021-Keynote-Daniel_Borkmann-BPF_and_Spectre.pdf > >This should go above the signed-off-by line, in the changelog text, not >below it, otherwise our tools get confused when trying to apply it. Thanks, I will fix it.
diff --git a/kernel/bpf/Kconfig b/kernel/bpf/Kconfig index a82d6de86522..510a5a73f9a2 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 if CPU_SPECTRE 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
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]. If an architecture selects CONFIG_CPU_SPECTRE, disable unprivileged BPF by default. An admin can enable this at runtime, if necessary. Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com> [1] https://ebpf.io/summit-2021-slides/eBPF_Summit_2021-Keynote-Daniel_Borkmann-BPF_and_Spectre.pdf --- kernel/bpf/Kconfig | 5 +++++ 1 file changed, 5 insertions(+)