[PATCH bpf-next 05/13] bpf: compute prog->digest at BPF_PROG_LOAD entry

[KP Singh]

add_subprog_and_kfunc relocates kfunc CALLs by patching insn->imm
and src_reg, and bpf_prog_calc_tag has no rule to mask kfunc CALL
fields. The tag has to be computed over the unmodified user-supplied
insns to match the excl_prog_hash userspace signed, so move the call
to bpf_prog_load right after signature verification.

Signed-off-by: KP Singh <kpsingh at kernel.org>
---
 kernel/bpf/syscall.c  | 7 +++++++
 kernel/bpf/verifier.c | 4 ----
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6d1db5eaad3c..39ebd825c136 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -3086,6 +3086,13 @@ static int bpf_prog_load(union bpf_attr *attr, bpfptr_t uattr, u32 uattr_size)
 	}
 	prog->aux->is_kernel = uattr.is_kernel;
 
+	/* Hash insns now, before any verifier-side rewrite, so prog->digest
+	 * matches the excl_prog_hash userspace computed.
+	 */
+	err = bpf_prog_calc_tag(prog);
+	if (err)
+		goto free_prog;
+
 	prog->orig_prog = NULL;
 	prog->jited = 0;
 
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 7fb88e1cd7c4..f0e45cfa5b34 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -18434,10 +18434,6 @@ static int check_and_resolve_insns(struct bpf_verifier_env *env)
 	int insn_cnt = env->prog->len;
 	int i, err;
 
-	err = bpf_prog_calc_tag(env->prog);
-	if (err)
-		return err;
-
 	for (i = 0; i < insn_cnt; i++, insn++) {
 		if (insn->dst_reg >= MAX_BPF_REG) {
 			verbose(env, "R%d is invalid\n", insn->dst_reg);
-- 
2.53.0