Hi Greg,
On Mon, Jul 24, 2023 at 03:42:18PM GMT, Eduard Zingerman wrote:
> [ Upstream commit be2ef8161572ec1973124ebc50f56dafc2925e07 ]
>
...
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
...
> @@ -2670,6 +2679,11 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx,
> */
> if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL && insn->imm == 0)
> return -ENOTSUPP;
> + /* BPF helpers that invoke callback subprogs are
> + * equivalent to BPF_PSEUDO_CALL above
> + */
> + if (insn->src_reg == 0 && is_callback_calling_function(insn->imm))
> + return -ENOTSUPP;
> /* regular helper call sets R0 */
> *reg_mask &= ~1;
> if (*reg_mask & 0x3f) {
Looks like the above hunk is slightly misplaced.
In master the lines are added _before_ the BPF_PSEUDO_KFUNC_CALL check,
resulting in deviation from upstream as well as interfering with
backporting of commit be2ef8161572 ("bpf: allow precision tracking for
programs with subprogs") to stable v6.1.
What would be the suggested action here?
1. Send a updated version of the whole be2ef8161572 patch to stable
2. Send a minimal refresh patch like the one found in this email to
stable
3. Adapt to this deviation in my backport of commit be2ef8161572 for
stable
Shung-Hsi
...
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 5d4510fb2be7..227dc10f6baa 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2673,17 +2673,17 @@ static int backtrack_insn(struct bpf_verifier_env *env, int idx,
if (opcode == BPF_CALL) {
if (insn->src_reg == BPF_PSEUDO_CALL)
return -ENOTSUPP;
+ /* BPF helpers that invoke callback subprogs are
+ * equivalent to BPF_PSEUDO_CALL above
+ */
+ if (insn->src_reg == 0 && is_callback_calling_function(insn->imm))
+ return -ENOTSUPP;
/* kfunc with imm==0 is invalid and fixup_kfunc_call will
* catch this error later. Make backtracking conservative
* with ENOTSUPP.
*/
if (insn->src_reg == BPF_PSEUDO_KFUNC_CALL && insn->imm == 0)
return -ENOTSUPP;
- /* BPF helpers that invoke callback subprogs are
- * equivalent to BPF_PSEUDO_CALL above
- */
- if (insn->src_reg == 0 && is_callback_calling_function(insn->imm))
- return -ENOTSUPP;
/* regular helper call sets R0 */
*reg_mask &= ~1;
if (*reg_mask & 0x3f) {
