Unit test for unitialized memory afer bpf_xdp_adjust_head

Reviewed By: frankfeir Differential Revision: D51536069 fbshipit-source-id: a9d3405a8c7da45300e8368b4e7785350143024f
facebookincubator · Nov 29, 2023 · e5a32cc · e5a32cc
1 parent 26b7273
commit e5a32cc
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Showing 3 changed files with 41 additions and 10 deletions.
diff --git a/katran/lib/bpf/balancer_helpers.h b/katran/lib/bpf/balancer_helpers.h
@@ -111,4 +111,35 @@ decrement_ttl(void* data, void* data_end, int offset, bool is_ipv6) {
   return FURTHER_PROCESSING;
 }
 
+__attribute__((__always_inline__)) static inline long test_bpf_xdp_adjust_head(
+    struct xdp_md* xdp_md,
+    int delta) {
+  long ret = bpf_xdp_adjust_head(xdp_md, delta);
+  if (ret) {
+    return ret;
+  }
+  if (delta >= 0) {
+    return ret;
+  }
+  // we've prepended "new" memory, initialize it
+
+  void* data = (void*)(long)xdp_md->data;
+  void* data_end = (void*)(long)xdp_md->data_end;
+  int offset = 0 - delta;
+  // extra check to make bpf verifier happy
+  if (data + offset > data_end) {
+    return -1;
+  }
+  // intentionally set all bits 1, as bpf tester zeros allocated memory, unlike
+  // xdp stack
+  memset(data, 0xFF, offset);
+  return ret;
+}
+
+#ifdef KATRAN_TEST_MODE
+#define XDP_ADJUST_HEAD_FUNC test_bpf_xdp_adjust_head
+#else
+#define XDP_ADJUST_HEAD_FUNC bpf_xdp_adjust_head
 #endif
+
+#endif // __BALANCER_HELPERS
diff --git a/katran/lib/bpf/handle_icmp.h b/katran/lib/bpf/handle_icmp.h
@@ -121,7 +121,7 @@ __attribute__((__always_inline__)) static inline int send_icmp6_reply(
 __attribute__((__always_inline__)) static inline int send_icmp4_too_big(
     struct xdp_md* xdp) {
   int headroom = (int)sizeof(struct iphdr) + (int)sizeof(struct icmphdr);
-  if (bpf_xdp_adjust_head(xdp, 0 - headroom)) {
+  if (XDP_ADJUST_HEAD_FUNC(xdp, 0 - headroom)) {
     return XDP_DROP;
   }
   void* data = (void*)(long)xdp->data;
@@ -169,7 +169,7 @@ __attribute__((__always_inline__)) static inline int send_icmp4_too_big(
 __attribute__((__always_inline__)) static inline int send_icmp6_too_big(
     struct xdp_md* xdp) {
   int headroom = (int)sizeof(struct ipv6hdr) + (int)sizeof(struct icmp6hdr);
-  if (bpf_xdp_adjust_head(xdp, 0 - headroom)) {
+  if (XDP_ADJUST_HEAD_FUNC(xdp, 0 - headroom)) {
     return XDP_DROP;
   }
   void* data = (void*)(long)xdp->data;

diff --git a/katran/lib/bpf/pckt_encap.h b/katran/lib/bpf/pckt_encap.h
@@ -56,7 +56,7 @@ __attribute__((__always_inline__)) static inline bool encap_v6(
   __u32 saddr[4];
   __u8 proto;
   // ip(6)ip6 encap
-  if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(struct ipv6hdr))) {
+  if (XDP_ADJUST_HEAD_FUNC(xdp, 0 - (int)sizeof(struct ipv6hdr))) {
     return false;
   }
   data = (void*)(long)xdp->data;
@@ -107,7 +107,7 @@ __attribute__((__always_inline__)) static inline bool encap_v4(
   ip_suffix ^= pckt->flow.src;
   __u64 csum = 0;
   // ipip encap
-  if (bpf_xdp_adjust_head(xdp, 0 - (int)sizeof(struct iphdr))) {
+  if (XDP_ADJUST_HEAD_FUNC(xdp, 0 - (int)sizeof(struct iphdr))) {
     return false;
   }
   data = (void*)(long)xdp->data;
@@ -148,7 +148,7 @@ decap_v6(struct xdp_md* xdp, void** data, void** data_end, bool inner_v4) {
   } else {
     new_eth->h_proto = BE_ETH_P_IPV6;
   }
-  if (bpf_xdp_adjust_head(xdp, (int)sizeof(struct ipv6hdr))) {
+  if (XDP_ADJUST_HEAD_FUNC(xdp, (int)sizeof(struct ipv6hdr))) {
     return false;
   }
   *data = (void*)(long)xdp->data;
@@ -165,7 +165,7 @@ decap_v4(struct xdp_md* xdp, void** data, void** data_end) {
   memcpy(new_eth->h_source, old_eth->h_source, 6);
   memcpy(new_eth->h_dest, old_eth->h_dest, 6);
   new_eth->h_proto = BE_ETH_P_IP;
-  if (bpf_xdp_adjust_head(xdp, (int)sizeof(struct iphdr))) {
+  if (XDP_ADJUST_HEAD_FUNC(xdp, (int)sizeof(struct iphdr))) {
     return false;
   }
   *data = (void*)(long)xdp->data;
@@ -274,7 +274,7 @@ __attribute__((__always_inline__)) static inline bool gue_encap_v4(
 
   sport ^= ((pckt->flow.src >> 16) & 0xFFFF);
 
-  if (bpf_xdp_adjust_head(
+  if (XDP_ADJUST_HEAD_FUNC(
           xdp, 0 - ((int)sizeof(struct iphdr) + (int)sizeof(struct udphdr)))) {
     return false;
   }
@@ -330,7 +330,7 @@ __attribute__((__always_inline__)) static inline bool gue_encap_v6(
     return false;
   }
 
-  if (bpf_xdp_adjust_head(
+  if (XDP_ADJUST_HEAD_FUNC(
           xdp,
           0 - ((int)sizeof(struct ipv6hdr) + (int)sizeof(struct udphdr)))) {
     return false;
@@ -380,7 +380,7 @@ gue_decap_v4(struct xdp_md* xdp, void** data, void** data_end) {
   memcpy(new_eth->h_source, old_eth->h_source, 6);
   memcpy(new_eth->h_dest, old_eth->h_dest, 6);
   new_eth->h_proto = BE_ETH_P_IP;
-  if (bpf_xdp_adjust_head(
+  if (XDP_ADJUST_HEAD_FUNC(
           xdp, (int)(sizeof(struct iphdr) + sizeof(struct udphdr)))) {
     return false;
   }
@@ -403,7 +403,7 @@ gue_decap_v6(struct xdp_md* xdp, void** data, void** data_end, bool inner_v4) {
   } else {
     new_eth->h_proto = BE_ETH_P_IPV6;
   }
-  if (bpf_xdp_adjust_head(
+  if (XDP_ADJUST_HEAD_FUNC(
           xdp, (int)(sizeof(struct ipv6hdr) + sizeof(struct udphdr)))) {
     return false;
   }