bpf: Use scalar ids in mark_chain_precision()

Change mark_chain_precision() to track precision in situations
like below:

    r2 = unknown value
    ...
  --- state #0 ---
    ...
    r1 = r2                 // r1 and r2 now share the same ID
    ...
  --- state #1 {r1.id = A, r2.id = A} ---
    ...
    if (r2 > 10) goto exit; // find_equal_scalars() assigns range to r1
    ...
  --- state #2 {r1.id = A, r2.id = A} ---
    r3 = r10
    r3 += r1                // need to mark both r1 and r2

At the beginning of the processing of each state, ensure that if a
register with a scalar ID is marked as precise, all registers sharing
this ID are also marked as precise.

This property would be used by a follow-up change in regsafe().

Signed-off-by: Eduard Zingerman <[email protected]>
Signed-off-by: Andrii Nakryiko <[email protected]>
Acked-by: Andrii Nakryiko <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]

1 files changed, 9 insertions, 1 deletions

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 5b11a3b0fec0..22fb13c738a9 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -557,6 +557,11 @@ struct backtrack_state {
 	u64 stack_masks[MAX_CALL_FRAMES];
 };
 
+struct bpf_idset {
+	u32 count;
+	u32 ids[BPF_ID_MAP_SIZE];
+};
+
 /* single container for all structs
  * one verifier_env per bpf_check() call
  */
@@ -588,7 +593,10 @@ struct bpf_verifier_env {
 	const struct bpf_line_info *prev_linfo;
 	struct bpf_verifier_log log;
 	struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 1];
-	struct bpf_id_pair idmap_scratch[BPF_ID_MAP_SIZE];
+	union {
+		struct bpf_id_pair idmap_scratch[BPF_ID_MAP_SIZE];
+		struct bpf_idset idset_scratch;
+	};
 	struct {
 		int *insn_state;
 		int *insn_stack;