| Message ID | 20211012123056.485795-1-hbathini@linux.ibm.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | bpf powerpc: Add BPF_PROBE_MEM support in powerpc JIT compiler | expand |
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)
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.
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)
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
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. Resending v4 after rebasing the series on top of bpf fix patches posted by Naveen: - https://patchwork.ozlabs.org/project/linuxppc-dev/cover/cover.1633464148.git.naveen.n.rao@linux.vnet.ibm.com/ ("[v2,00/10] powerpc/bpf: Various fixes") Also, added Reviewed-by tag from Christophe for patches #3, #5, #6, #7 & #8. Hari Bathini (4): bpf powerpc: refactor JIT compiler code powerpc/ppc-opcode: introduce PPC_RAW_BRANCH() macro bpf ppc32: Add BPF_PROBE_MEM support for JIT bpf ppc32: Access only if addr is kernel address Ravi Bangoria (4): bpf powerpc: Remove unused SEEN_STACK bpf powerpc: Remove extra_pass from bpf_jit_build_body() bpf ppc64: Add BPF_PROBE_MEM support for JIT bpf ppc64: Access only if addr is kernel address arch/powerpc/include/asm/ppc-opcode.h | 2 + arch/powerpc/net/bpf_jit.h | 17 ++++- arch/powerpc/net/bpf_jit_comp.c | 68 +++++++++++++++-- arch/powerpc/net/bpf_jit_comp32.c | 101 ++++++++++++++++++++++---- arch/powerpc/net/bpf_jit_comp64.c | 72 ++++++++++++++---- 5 files changed, 219 insertions(+), 41 deletions(-)