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>
We can merge this at -rc1.
Will
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