Re: [RESEND PATCH v4 0/8] bpf powerpc: Add BPF_PROBE_MEM support in powerpc JIT compiler
On Tue, 12 Oct 2021 18:00:48 +0530, Hari Bathini wrote: > Patch #1 & #2 are simple cleanup patches. Patch #3 refactors JIT > compiler code with the aim to simplify adding BPF_PROBE_MEM support. > Patch #4 introduces PPC_RAW_BRANCH() macro instead of open coding > branch instruction. Patch #5 & #7 add BPF_PROBE_MEM support for PPC64 > & PPC32 JIT compilers respectively. Patch #6 & #8 handle bad userspace > pointers for PPC64 & PPC32 cases respectively. > > [...] Applied to powerpc/next. [1/8] bpf powerpc: Remove unused SEEN_STACK https://git.kernel.org/powerpc/c/c9ce7c36e4870bd307101ba7a00a39d9aad270f3 [2/8] bpf powerpc: Remove extra_pass from bpf_jit_build_body() https://git.kernel.org/powerpc/c/04c04205bc35d0ecdc57146995ca9eb957d4f379 [3/8] bpf powerpc: refactor JIT compiler code https://git.kernel.org/powerpc/c/efa95f031bf38c85cf865413335a3dc044e3194e [4/8] powerpc/ppc-opcode: introduce PPC_RAW_BRANCH() macro https://git.kernel.org/powerpc/c/f15a71b3880bf07b40810644e5ac6f177c2a7c8f [5/8] bpf ppc64: Add BPF_PROBE_MEM support for JIT https://git.kernel.org/powerpc/c/983bdc0245a29cdefcd30d9d484d3edbc4b6d787 [6/8] bpf ppc64: Access only if addr is kernel address https://git.kernel.org/powerpc/c/9c70c7147ffec31de67d33243570a533b29f9759 [7/8] bpf ppc32: Add BPF_PROBE_MEM support for JIT https://git.kernel.org/powerpc/c/23b51916ee129833453d8a3d6bde0ff392f82fce [8/8] bpf ppc32: Access only if addr is kernel address https://git.kernel.org/powerpc/c/e919c0b2323bedec00e1ecc6280498ff81f59b15 cheers
RE: [RESEND PATCH v4 0/8] bpf powerpc: Add BPF_PROBE_MEM support in powerpc JIT compiler
From: Christophe Leroy
> Sent: 14 October 2021 09:34
>
> Le 14/10/2021 à 10:15, David Laight a écrit :
> > From: Hari Bathini
> >> Sent: 12 October 2021 13:31
> >>
> >> Patch #1 & #2 are simple cleanup patches. Patch #3 refactors JIT
> >> compiler code with the aim to simplify adding BPF_PROBE_MEM support.
> >> Patch #4 introduces PPC_RAW_BRANCH() macro instead of open coding
> >> branch instruction. Patch #5 & #7 add BPF_PROBE_MEM support for PPC64
> >> & PPC32 JIT compilers respectively. Patch #6 & #8 handle bad userspace
> >> pointers for PPC64 & PPC32 cases respectively.
> >
> > I thought that BPF was only allowed to do fairly restricted
> > memory accesses - so WTF does it need a BPF_PROBE_MEM instruction?
> >
>
>
> Looks like it's been added by commit 2a02759ef5f8 ("bpf: Add support for
> BTF pointers to interpreter")
>
> They say in the log:
>
> Pointer to BTF object is a pointer to kernel object or NULL.
> The memory access in the interpreter has to be done via
> probe_kernel_read to avoid page faults.
Hmmm
Either the pointer should be valid (if not NULL) or they should
verify that it is the address of an interpreter.
If the value is being passed to/from userspace then they
are leaking kernel address - and that needs to be squashed.
They should be using an opaque identifier for the interpreter.
My gut feeling is that a lot of the changes to bpf over the last
few years means that it is no longer a verifiably safe simple
filter engine.
As such the you might as well load a normal kernel module.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT,
UK
Registration No: 1397386 (Wales)
Re: [RESEND PATCH v4 0/8] bpf powerpc: Add BPF_PROBE_MEM support in powerpc JIT compiler
Le 14/10/2021 à 10:15, David Laight a écrit :
From: Hari Bathini
Sent: 12 October 2021 13:31
Patch #1 & #2 are simple cleanup patches. Patch #3 refactors JIT
compiler code with the aim to simplify adding BPF_PROBE_MEM support.
Patch #4 introduces PPC_RAW_BRANCH() macro instead of open coding
branch instruction. Patch #5 & #7 add BPF_PROBE_MEM support for PPC64
& PPC32 JIT compilers respectively. Patch #6 & #8 handle bad userspace
pointers for PPC64 & PPC32 cases respectively.
I thought that BPF was only allowed to do fairly restricted
memory accesses - so WTF does it need a BPF_PROBE_MEM instruction?
Looks like it's been added by commit 2a02759ef5f8 ("bpf: Add support for
BTF pointers to interpreter")
They say in the log:
Pointer to BTF object is a pointer to kernel object or NULL.
The memory access in the interpreter has to be done via
probe_kernel_read
to avoid page faults.
RE: [RESEND PATCH v4 0/8] bpf powerpc: Add BPF_PROBE_MEM support in powerpc JIT compiler
From: Hari Bathini > Sent: 12 October 2021 13:31 > > Patch #1 & #2 are simple cleanup patches. Patch #3 refactors JIT > compiler code with the aim to simplify adding BPF_PROBE_MEM support. > Patch #4 introduces PPC_RAW_BRANCH() macro instead of open coding > branch instruction. Patch #5 & #7 add BPF_PROBE_MEM support for PPC64 > & PPC32 JIT compilers respectively. Patch #6 & #8 handle bad userspace > pointers for PPC64 & PPC32 cases respectively. I thought that BPF was only allowed to do fairly restricted memory accesses - so WTF does it need a BPF_PROBE_MEM instruction? David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
