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In userland, sign extend the offset for JA instructions.

We currently use that to implement "ip6 protochain", and "pc" might be
wider than "pc->k", in which case we need to arrange that "pc->k" be
sign-extended, by casting it to bpf_int32.
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1 parent f3e011b commit ecdc5c0a7f7591a7cd4aff696e42757c677fbbf7 @guyharris guyharris committed May 5, 2011
Showing with 11 additions and 0 deletions.
  1. +11 −0 bpf/net/bpf_filter.c
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@@ -405,7 +405,18 @@ bpf_filter(pc, p, wirelen, buflen)
continue;
case BPF_JMP|BPF_JA:
+#if defined(KERNEL) || defined(_KERNEL)
+ /*
+ * No backward jumps allowed.
+ */
pc += pc->k;
+#else
+ /*
+ * XXX - we currently implement "ip6 protochain"
+ * with backward jumps, so sign-extend pc->k.
+ */
+ pc += (bpf_int32)pc->k;
+#endif
continue;
case BPF_JMP|BPF_JGT|BPF_K:

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