bpf: Move sanitize_val_alu out of op switch

commit f528819334881fd622fdadeddb3f7edaed8b7c9b upstream.

Add a small sanitize_needed() helper function and move sanitize_val_alu()
out of the main opcode switch. In upcoming work, we'll move sanitize_ptr_alu()
as well out of its opcode switch so this helps to streamline both.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
[fllinden@amazon.com: backported to 4.14]
Signed-off-by: Frank van der Linden <fllinden@amazon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index d178098f2298074d68e7a0e16f5e452ee9a41be8..f76177a37b189fab520a98f9bafaa8901d4ce733 100644 (file)
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2110,6 +2110,11 @@ static int sanitize_val_alu(struct bpf_verifier_env *env,
        return update_alu_sanitation_state(aux, BPF_ALU_NON_POINTER, 0);
 }
 
+static bool sanitize_needed(u8 opcode)
+{
+       return opcode == BPF_ADD || opcode == BPF_SUB;
+}
+
 static int sanitize_ptr_alu(struct bpf_verifier_env *env,
                            struct bpf_insn *insn,
                            const struct bpf_reg_state *ptr_reg,
@@ -2510,11 +2515,14 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
                return 0;
        }
 
-       switch (opcode) {
-       case BPF_ADD:
+       if (sanitize_needed(opcode)) {
                ret = sanitize_val_alu(env, insn);
                if (ret < 0)
                        return sanitize_err(env, insn, ret, NULL, NULL);
+       }
+
+       switch (opcode) {
+       case BPF_ADD:
                if (signed_add_overflows(dst_reg->smin_value, smin_val) ||
                    signed_add_overflows(dst_reg->smax_value, smax_val)) {
                        dst_reg->smin_value = S64_MIN;
@@ -2534,9 +2542,6 @@ static int adjust_scalar_min_max_vals(struct bpf_verifier_env *env,
                dst_reg->var_off = tnum_add(dst_reg->var_off, src_reg.var_off);
                break;
        case BPF_SUB:
-               ret = sanitize_val_alu(env, insn);
-               if (ret < 0)
-                       return sanitize_err(env, insn, ret, NULL, NULL);
                if (signed_sub_overflows(dst_reg->smin_value, smax_val) ||
                    signed_sub_overflows(dst_reg->smax_value, smin_val)) {
                        /* Overflow possible, we know nothing */