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Date: Tue, 16 Sep 2014 09:29:30 -0700 From: Z Lim <zlim.lnx@...il.com> To: Will Deacon <will.deacon@....com> Cc: Daniel Borkmann <dborkman@...hat.com>, Catalin Marinas <Catalin.Marinas@....com>, "linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "David S. Miller" <davem@...emloft.net>, Alexei Starovoitov <ast@...mgrid.com> Subject: Re: [PATCH arm64-next v4] net: bpf: arm64: address randomize and write protect JIT code On Tue, Sep 16, 2014 at 9:25 AM, Will Deacon <will.deacon@....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 <dborkman@...hat.com> >> Cc: Zi Shen Lim <zlim.lnx@...il.com> >> Cc: Will Deacon <will.deacon@....com> >> Cc: Catalin Marinas <catalin.marinas@....com> >> Cc: David S. Miller <davem@...emloft.net> >> Cc: Alexei Starovoitov <ast@...mgrid.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.deacon@....com> > Reviewed-by: Zi Shen Lim <zlim.lnx@...il.com> > We can merge this at -rc1. > > Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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