bpf: recognize 64bit immediate loads as consts

When running as parser interpret BPF_LD | BPF_IMM | BPF_DW
instructions as loading CONST_IMM with the value stored
in imm.  The verifier will continue not recognizing those
due to concerns about search space/program complexity
increase.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 2 deletions

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index ee86a77dc40b..8c3f794c7028 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1769,9 +1769,19 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
         if (err)
                 return err;
 
-        if (insn->src_reg == 0)
-                /* generic move 64-bit immediate into a register */
+        if (insn->src_reg == 0) {
+                /* generic move 64-bit immediate into a register,
+                 * only analyzer needs to collect the ld_imm value.
+                 */
+                u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
+
+                if (!env->analyzer_ops)
+                        return 0;
+
+                regs[insn->dst_reg].type = CONST_IMM;
+                regs[insn->dst_reg].imm = imm;
                 return 0;
+        }
 
         /* replace_map_fd_with_map_ptr() should have caught bad ld_imm64 */
         BUG_ON(insn->src_reg != BPF_PSEUDO_MAP_FD);