From 91fc957c9b1d6c55168df15a397cbd1af16bc00f Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Fri, 23 Nov 2018 23:18:04 +0100 Subject: arm64/bpf: don't allocate BPF JIT programs in module memory The arm64 module region is a 128 MB region that is kept close to the core kernel, in order to ensure that relative branches are always in range. So using the same region for programs that do not have this restriction is wasteful, and preferably avoided. Now that the core BPF JIT code permits the alloc/free routines to be overridden, implement them by vmalloc()/vfree() calls from a dedicated 128 MB region set aside for BPF programs. This ensures that BPF programs are still in branching range of each other, which is something the JIT currently depends upon (and is not guaranteed when using module_alloc() on KASLR kernels like we do currently). It also ensures that placement of BPF programs does not correlate with the placement of the core kernel or modules, making it less likely that leaking the former will reveal the latter. This also solves an issue under KASAN, where shadow memory is needlessly allocated for all BPF programs (which don't require KASAN shadow pages since they are not KASAN instrumented) Signed-off-by: Ard Biesheuvel Acked-by: Will Deacon Signed-off-by: Daniel Borkmann --- arch/arm64/net/bpf_jit_comp.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'arch/arm64/net') diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index b87285924023..0a7371a86139 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -943,3 +943,16 @@ out: tmp : orig_prog); return prog; } + +void *bpf_jit_alloc_exec(unsigned long size) +{ + return __vmalloc_node_range(size, PAGE_SIZE, BPF_JIT_REGION_START, + BPF_JIT_REGION_END, GFP_KERNEL, + PAGE_KERNEL_EXEC, 0, NUMA_NO_NODE, + __builtin_return_address(0)); +} + +void bpf_jit_free_exec(void *addr) +{ + return vfree(addr); +} -- cgit v1.2.3