powerpc/bpf: Flush the entire JIT buffer

With bpf_jit_binary_alloc(), we allocate at a page granularity and fill
the rest of the space with illegal instructions to mitigate BPF spraying
attacks, while having the actual JIT'ed BPF program at a random location
within the allocated space. Under this scenario, it would be better to
flush the entire allocated buffer rather than just the part containing
the actual program. We already flush the buffer from start to the end of
the BPF program. Extend this to include the illegal instructions after
the BPF program.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
index 935a10f77cfe8afab7f42338934fc5e209fd00b7..d4ed7a0872b1d6e0c1af9976c164206319738106 100644 (file)
--- a/arch/powerpc/net/bpf_jit_comp64.c
+++ b/arch/powerpc/net/bpf_jit_comp64.c
@@ -1046,8 +1046,6 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
                 */
                bpf_jit_dump(flen, proglen, pass, code_base);
 
-       bpf_flush_icache(bpf_hdr, image + alloclen);
-
 #ifdef PPC64_ELF_ABI_v1
        /* Function descriptor nastiness: Address + TOC */
        ((u64 *)image)[0] = (u64)code_base;
@@ -1057,6 +1055,8 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
        fp->bpf_func = (void *)image;
        fp->jited = 1;
 
+       bpf_flush_icache(bpf_hdr, (u8 *)bpf_hdr + (bpf_hdr->pages * PAGE_SIZE));
+
 out:
        kfree(addrs);