bpf: fix pointer offsets in context for 32 bit

Currently, pointer offsets in three BPF context structures are
broken in two scenarios: i) 32 bit compiled applications running
on 64 bit kernels, and ii) LLVM compiled BPF programs running
on 32 bit kernels. The latter is due to BPF target machine being
strictly 64 bit. So in each of the cases the offsets will mismatch
in verifier when checking / rewriting context access. Fix this by
providing a helper macro __bpf_md_ptr() that will enforce padding
up to 64 bit and proper alignment, and for context access a macro
bpf_ctx_range_ptr() which will cover full 64 bit member range on
32 bit archs. For flow_keys, we additionally need to force the
size check to sizeof(__u64) as with other pointer types.

Fixes: d58e468b1112 ("flow_dissector: implements flow dissector BPF hook")
Fixes: 4f738adba30a ("bpf: create tcp_bpf_ulp allowing BPF to monitor socket TX/RX data")
Fixes: 2dbb9b9e6df6 ("bpf: Introduce BPF_PROG_TYPE_SK_REUSEPORT")
Reported-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: David S. Miller <davem@davemloft.net>
Tested-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 8 insertions, 8 deletions

diff --git a/net/core/filter.c b/net/core/filter.c
index 9a1327eb25fa..6ee605da990f 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -5435,8 +5435,8 @@ static bool bpf_skb_is_valid_access(int off, int size, enum bpf_access_type type
                 if (size != size_default)
                         return false;
                 break;
-        case bpf_ctx_range(struct __sk_buff, flow_keys):
-                if (size != sizeof(struct bpf_flow_keys *))
+        case bpf_ctx_range_ptr(struct __sk_buff, flow_keys):
+                if (size != sizeof(__u64))
                         return false;
                 break;
         default:
@@ -5464,7 +5464,7 @@ static bool sk_filter_is_valid_access(int off, int size,
         case bpf_ctx_range(struct __sk_buff, data):
         case bpf_ctx_range(struct __sk_buff, data_meta):
         case bpf_ctx_range(struct __sk_buff, data_end):
-        case bpf_ctx_range(struct __sk_buff, flow_keys):
+        case bpf_ctx_range_ptr(struct __sk_buff, flow_keys):
         case bpf_ctx_range_till(struct __sk_buff, family, local_port):
                 return false;
         }
@@ -5489,7 +5489,7 @@ static bool cg_skb_is_valid_access(int off, int size,
         switch (off) {
         case bpf_ctx_range(struct __sk_buff, tc_classid):
         case bpf_ctx_range(struct __sk_buff, data_meta):
-        case bpf_ctx_range(struct __sk_buff, flow_keys):
+        case bpf_ctx_range_ptr(struct __sk_buff, flow_keys):
                 return false;
         case bpf_ctx_range(struct __sk_buff, data):
         case bpf_ctx_range(struct __sk_buff, data_end):
@@ -5530,7 +5530,7 @@ static bool lwt_is_valid_access(int off, int size,
         case bpf_ctx_range(struct __sk_buff, tc_classid):
         case bpf_ctx_range_till(struct __sk_buff, family, local_port):
         case bpf_ctx_range(struct __sk_buff, data_meta):
-        case bpf_ctx_range(struct __sk_buff, flow_keys):
+        case bpf_ctx_range_ptr(struct __sk_buff, flow_keys):
                 return false;
         }
 
@@ -5756,7 +5756,7 @@ static bool tc_cls_act_is_valid_access(int off, int size,
         case bpf_ctx_range(struct __sk_buff, data_end):
                 info->reg_type = PTR_TO_PACKET_END;
                 break;
-        case bpf_ctx_range(struct __sk_buff, flow_keys):
+        case bpf_ctx_range_ptr(struct __sk_buff, flow_keys):
         case bpf_ctx_range_till(struct __sk_buff, family, local_port):
                 return false;
         }
@@ -5958,7 +5958,7 @@ static bool sk_skb_is_valid_access(int off, int size,
         switch (off) {
         case bpf_ctx_range(struct __sk_buff, tc_classid):
         case bpf_ctx_range(struct __sk_buff, data_meta):
-        case bpf_ctx_range(struct __sk_buff, flow_keys):
+        case bpf_ctx_range_ptr(struct __sk_buff, flow_keys):
                 return false;
         }
 
@@ -6039,7 +6039,7 @@ static bool flow_dissector_is_valid_access(int off, int size,
         case bpf_ctx_range(struct __sk_buff, data_end):
                 info->reg_type = PTR_TO_PACKET_END;
                 break;
-        case bpf_ctx_range(struct __sk_buff, flow_keys):
+        case bpf_ctx_range_ptr(struct __sk_buff, flow_keys):
                 info->reg_type = PTR_TO_FLOW_KEYS;
                 break;
         case bpf_ctx_range(struct __sk_buff, tc_classid):