bpf: fix matching of data/data_end in verifier

The ctx structure passed into bpf programs is different depending on bpf
program type. The verifier incorrectly marked ctx->data and ctx->data_end
access based on ctx offset only. That caused loads in tracing programs
int bpf_prog(struct pt_regs *ctx) { .. ctx->ax .. }
to be incorrectly marked as PTR_TO_PACKET which later caused verifier
to reject the program that was actually valid in tracing context.
Fix this by doing program type specific matching of ctx offsets.

Fixes: 969bf05eb3ce ("bpf: direct packet access")
Reported-by: Sasha Goldshtein <goldshtn@gmail.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 2 deletions

diff --git a/net/core/filter.c b/net/core/filter.c
index 68adb5f52110..c4b330c85c02 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2085,7 +2085,8 @@ static bool __is_valid_access(int off, int size, enum bpf_access_type type)
 }
 
 static bool sk_filter_is_valid_access(int off, int size,
-				      enum bpf_access_type type)
+				      enum bpf_access_type type,
+				      enum bpf_reg_type *reg_type)
 {
 	switch (off) {
 	case offsetof(struct __sk_buff, tc_classid):
@@ -2108,7 +2109,8 @@ static bool sk_filter_is_valid_access(int off, int size,
 }
 
 static bool tc_cls_act_is_valid_access(int off, int size,
-				       enum bpf_access_type type)
+				       enum bpf_access_type type,
+				       enum bpf_reg_type *reg_type)
 {
 	if (type == BPF_WRITE) {
 		switch (off) {
@@ -2123,6 +2125,16 @@ static bool tc_cls_act_is_valid_access(int off, int size,
 			return false;
 		}
 	}
+
+	switch (off) {
+	case offsetof(struct __sk_buff, data):
+		*reg_type = PTR_TO_PACKET;
+		break;
+	case offsetof(struct __sk_buff, data_end):
+		*reg_type = PTR_TO_PACKET_END;
+		break;
+	}
+
 	return __is_valid_access(off, size, type);
 }