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

[John Fastabend]

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.fastab...@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;
        }