[net-next PATCH 6/9] bpf: harden sockmap program attach to ensure correct map type

John Fastabend
2017-08-28T14:11:56Z

When attaching a program to sockmap we need to check map type
is correct.

Fixes: 174a79ff9515 ("bpf: sockmap with sk redirect support")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
---
kernel/bpf/sockmap.c | 3 ++
tools/testing/selftests/bpf/sockmap_verdict_prog.c | 7 +++++
tools/testing/selftests/bpf/test_maps.c | 27 +++++++++++++++++---
3 files changed, 33 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 266011c8..38bf4e4 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c
@@ -794,6 +794,9 @@ int sock_map_attach_prog(struct bpf_map *map, struct bpf_prog *prog, u32 type)
struct bpf_stab *stab = container_of(map, struct bpf_stab, map);
struct bpf_prog *orig;

+ if (unlikely(map->map_type != BPF_MAP_TYPE_SOCKMAP))
+ return -EINVAL;
+
switch (type) {
case BPF_SK_SKB_STREAM_PARSER:
orig = xchg(&stab->bpf_parse, prog);
diff --git a/tools/testing/selftests/bpf/sockmap_verdict_prog.c b/tools/testing/selftests/bpf/sockmap_verdict_prog.c
index dada207..9b99bd1 100644
--- a/tools/testing/selftests/bpf/sockmap_verdict_prog.c
+++ b/tools/testing/selftests/bpf/sockmap_verdict_prog.c
@@ -26,6 +26,13 @@ struct bpf_map_def SEC("maps") sock_map_tx = {
.max_entries = 20,
};

+struct bpf_map_def SEC("maps") sock_map_break = {
+ .type = BPF_MAP_TYPE_ARRAY,
+ .key_size = sizeof(int),
+ .value_size = sizeof(int),
+ .max_entries = 20,
+};
+
SEC("sk_skb2")
int bpf_prog2(struct __sk_buff *skb)
{
diff --git a/tools/testing/selftests/bpf/test_maps.c b/tools/testing/selftests/bpf/test_maps.c
index 0a7f457..0c4b56d 100644
--- a/tools/testing/selftests/bpf/test_maps.c
+++ b/tools/testing/selftests/bpf/test_maps.c
@@ -463,12 +463,12 @@ static void test_devmap(int task, void *data)
#define SOCKMAP_VERDICT_PROG "./sockmap_verdict_prog.o"
static void test_sockmap(int task, void *data)
{
+ int one = 1, map_fd_rx, map_fd_tx, map_fd_break, s, sc, rc;
+ struct bpf_map *bpf_map_rx, *bpf_map_tx, *bpf_map_break;
int ports[] = {50200, 50201, 50202, 50204};
int err, i, fd, sfd[6] = {0xdeadbeef};
u8 buf[20] = {0x0, 0x5, 0x3, 0x2, 0x1, 0x0};
- int one = 1, map_fd_rx, map_fd_tx, s, sc, rc;
int parse_prog, verdict_prog;
- struct bpf_map *bpf_map_rx, *bpf_map_tx;
struct sockaddr_in addr;
struct bpf_object *obj;
struct timeval to;
@@ -609,17 +609,36 @@ static void test_sockmap(int task, void *data)
goto out_sockmap;
}

+ bpf_map_break = bpf_object__find_map_by_name(obj, "sock_map_break");
+ if (IS_ERR(bpf_map_break)) {
+ printf("Failed to load map tx from verdict prog\n");
+ goto out_sockmap;
+ }
+
+ map_fd_break = bpf_map__fd(bpf_map_break);
+ if (map_fd_break < 0) {
+ printf("Failed to get map tx fd\n");
+ goto out_sockmap;
+ }
+
+ err = bpf_prog_attach(parse_prog, map_fd_break,
+ BPF_SK_SKB_STREAM_PARSER, 0);
+ if (!err) {
+ printf("Allowed attaching SK_SKB program to invalid map\n");
+ goto out_sockmap;
+ }
+
err = bpf_prog_attach(parse_prog, map_fd_rx,
BPF_SK_SKB_STREAM_PARSER, 0);
if (err) {
- printf("Failed bpf prog attach\n");
+ printf("Failed stream parser bpf prog attach\n");
goto out_sockmap;
}

err = bpf_prog_attach(verdict_prog, map_fd_rx,
BPF_SK_SKB_STREAM_VERDICT, 0);
if (err) {
- printf("Failed bpf prog attach\n");
+ printf("Failed stream verdict bpf prog attach\n");
goto out_sockmap;
}