On Tue, Sep 16, 2014 at 9:25 AM, Will Deacon <will.dea...@arm.com> wrote:
> On Tue, Sep 16, 2014 at 08:48:50AM +0100, Daniel Borkmann wrote:
>> This is the ARM64 variant for 314beb9bcab ("x86: bpf_jit_comp: secure bpf
>> jit against spraying attacks").
>>
>> Thanks to commit 11d91a770f1f ("arm64: Add CONFIG_DEBUG_SET_MODULE_RONX
>> support") which added necessary infrastructure, we can now implement
>> RO marking of eBPF generated JIT image pages and randomize start offset
>> for the JIT code, so that it does not reside directly on a page boundary
>> anymore. Likewise, the holes are filled with illegal instructions: here
>> we use BRK #0x100 (opcode 0xd4202000) to trigger a fault in the kernel
>> (unallocated BRKs would trigger a fault through do_debug_exception). This
>> seems more reliable as we don't have a guaranteed undefined instruction
>> space on ARM64.
>>
>> This is basically the ARM64 variant of what we already have in ARM via
>> commit 55309dd3d4cd ("net: bpf: arm: address randomize and write protect
>> JIT code"). Moreover, this commit also presents a merge resolution due to
>> conflicts with commit 60a3b2253c41 ("net: bpf: make eBPF interpreter images
>> read-only") as we don't use kfree() in bpf_jit_free() anymore to release
>> the locked bpf_prog structure, but instead bpf_prog_unlock_free() through
>> a different allocator.
>>
>> JIT tested on aarch64 with BPF test suite.
>>
>> Reference:
>> http://mainisusuallyafunction.blogspot.com/2012/11/attacking-hardened-linux-systems-with.html
>> Signed-off-by: Daniel Borkmann <dbork...@redhat.com>
>> Cc: Zi Shen Lim <zlim....@gmail.com>
>> Cc: Will Deacon <will.dea...@arm.com>
>> Cc: Catalin Marinas <catalin.mari...@arm.com>
>> Cc: David S. Miller <da...@davemloft.net>
>> Cc: Alexei Starovoitov <a...@plumgrid.com>
>> ---
>> v3->v4:
>> - Inclusion into debug-monitors.h as suggested by Will
>> v2->v3:
>> - Use cpu_to_le32() as suggested by Zi/Will
>> v1->v2:
>> - Use brk insn as suggested by Catalin
>> Note:
>> - This patch depends on net-next being merged to mainline due
>> to the mentioned merge conflict.
>>
>> arch/arm64/include/asm/debug-monitors.h | 8 +++++++
>> arch/arm64/net/bpf_jit_comp.c | 39
>> +++++++++++++++++++++++++--------
>> 2 files changed, 38 insertions(+), 9 deletions(-)
>
> Thanks, Daniel, this looks great:
>
> Acked-by: Will Deacon <will.dea...@arm.com>
>
Reviewed-by: Zi Shen Lim <zlim....@gmail.com>
> We can merge this at -rc1.
>
> Will
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