Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf

Daniel Borkmann says:

====================
pull-request: bpf 2020-07-31

The following pull-request contains BPF updates for your *net* tree.

We've added 5 non-merge commits during the last 21 day(s) which contain
a total of 5 files changed, 126 insertions(+), 18 deletions(-).

The main changes are:

1) Fix a map element leak in HASH_OF_MAPS map type, from Andrii Nakryiko.

2) Fix a NULL pointer dereference in __btf_resolve_helper_id() when no
   btf_vmlinux is available, from Peilin Ye.

3) Init pos variable in __bpfilter_process_sockopt(), from Christoph Hellwig.

4) Fix a cgroup sockopt verifier test by specifying expected attach type,
   from Jean-Philippe Brucker.

Note that when net gets merged into net-next later on, there is a small
merge conflict in kernel/bpf/btf.c between commit 5b801dfb ("bpf: Fix
NULL pointer dereference in __btf_resolve_helper_id()") from the bpf tree
and commit 138b9a05 ("bpf: Remove btf_id helpers resolving") from the
net-next tree.

Resolve as follows: remove the old hunk with the __btf_resolve_helper_id()
function. Change the btf_resolve_helper_id() so it actually tests for a
NULL btf_vmlinux and bails out:

int btf_resolve_helper_id(struct bpf_verifier_log *log,
                          const struct bpf_func_proto *fn, int arg)
{
        int id;

        if (fn->arg_type[arg] != ARG_PTR_TO_BTF_ID || !btf_vmlinux)
                return -EINVAL;
        id = fn->btf_id[arg];
        if (!id || id > btf_vmlinux->nr_types)
                return -EINVAL;
        return id;
}

Let me know if you run into any others issues (CC'ing Jiri Olsa so he's in
the loop with regards to merge conflict resolution).
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

kernel/bpf/btf.c

@@ -4058,6 +4058,11 @@ static int __btf_resolve_helper_id(struct bpf_verifier_log *log, void *fn,
 	const char *tname, *sym;
 	u32 btf_id, i;
 
+	if (!btf_vmlinux) {
+		bpf_log(log, "btf_vmlinux doesn't exist\n");
+		return -EINVAL;
+	}
+
 	if (IS_ERR(btf_vmlinux)) {
 		bpf_log(log, "btf_vmlinux is malformed\n");
 		return -EINVAL;

kernel/bpf/hashtab.c

@@ -779,15 +779,20 @@ static void htab_elem_free_rcu(struct rcu_head *head)
 	htab_elem_free(htab, l);
 }
 
-static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
+static void htab_put_fd_value(struct bpf_htab *htab, struct htab_elem *l)
 {
 	struct bpf_map *map = &htab->map;
+	void *ptr;
 
 	if (map->ops->map_fd_put_ptr) {
-		void *ptr = fd_htab_map_get_ptr(map, l);
-
+		ptr = fd_htab_map_get_ptr(map, l);
 		map->ops->map_fd_put_ptr(ptr);
 	}
+}
+
+static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
+{
+	htab_put_fd_value(htab, l);
 
 	if (htab_is_prealloc(htab)) {
 		__pcpu_freelist_push(&htab->freelist, &l->fnode);
@@ -839,6 +844,7 @@ static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
 			 */
 			pl_new = this_cpu_ptr(htab->extra_elems);
 			l_new = *pl_new;
+			htab_put_fd_value(htab, old_elem);
 			*pl_new = old_elem;
 		} else {
 			struct pcpu_freelist_node *l;

net/bpfilter/bpfilter_kern.c

@@ -39,7 +39,7 @@ static int __bpfilter_process_sockopt(struct sock *sk, int optname,
 {
 	struct mbox_request req;
 	struct mbox_reply reply;
-	loff_t pos;
+	loff_t pos = 0;
 	ssize_t n;
 	int ret = -EFAULT;
 

tools/testing/selftests/bpf/prog_tests/btf_map_in_map.c

@@ -5,10 +5,60 @@
 
 #include "test_btf_map_in_map.skel.h"
 
+static int duration;
+
+static __u32 bpf_map_id(struct bpf_map *map)
+{
+	struct bpf_map_info info;
+	__u32 info_len = sizeof(info);
+	int err;
+
+	memset(&info, 0, info_len);
+	err = bpf_obj_get_info_by_fd(bpf_map__fd(map), &info, &info_len);
+	if (err)
+		return 0;
+	return info.id;
+}
+
+/*
+ * Trigger synchronize_rcu() in kernel.
+ *
+ * ARRAY_OF_MAPS/HASH_OF_MAPS lookup/update operations trigger synchronize_rcu()
+ * if looking up an existing non-NULL element or updating the map with a valid
+ * inner map FD. Use this fact to trigger synchronize_rcu(): create map-in-map,
+ * create a trivial ARRAY map, update map-in-map with ARRAY inner map. Then
+ * cleanup. At the end, at least one synchronize_rcu() would be called.
+ */
+static int kern_sync_rcu(void)
+{
+	int inner_map_fd, outer_map_fd, err, zero = 0;
+
+	inner_map_fd = bpf_create_map(BPF_MAP_TYPE_ARRAY, 4, 4, 1, 0);
+	if (CHECK(inner_map_fd < 0, "inner_map_create", "failed %d\n", -errno))
+		return -1;
+
+	outer_map_fd = bpf_create_map_in_map(BPF_MAP_TYPE_ARRAY_OF_MAPS, NULL,
+					     sizeof(int), inner_map_fd, 1, 0);
+	if (CHECK(outer_map_fd < 0, "outer_map_create", "failed %d\n", -errno)) {
+		close(inner_map_fd);
+		return -1;
+	}
+
+	err = bpf_map_update_elem(outer_map_fd, &zero, &inner_map_fd, 0);
+	if (err)
+		err = -errno;
+	CHECK(err, "outer_map_update", "failed %d\n", err);
+	close(inner_map_fd);
+	close(outer_map_fd);
+	return err;
+}
+
 void test_btf_map_in_map(void)
 {
-	int duration = 0, err, key = 0, val;
-	struct test_btf_map_in_map* skel;
+	int err, key = 0, val, i;
+	struct test_btf_map_in_map *skel;
+	int outer_arr_fd, outer_hash_fd;
+	int fd, map1_fd, map2_fd, map1_id, map2_id;
 
 	skel = test_btf_map_in_map__open_and_load();
 	if (CHECK(!skel, "skel_open", "failed to open&load skeleton\n"))
@@ -18,32 +68,78 @@ void test_btf_map_in_map(void)
 	if (CHECK(err, "skel_attach", "skeleton attach failed: %d\n", err))
 		goto cleanup;
 
+	map1_fd = bpf_map__fd(skel->maps.inner_map1);
+	map2_fd = bpf_map__fd(skel->maps.inner_map2);
+	outer_arr_fd = bpf_map__fd(skel->maps.outer_arr);
+	outer_hash_fd = bpf_map__fd(skel->maps.outer_hash);
+
 	/* inner1 = input, inner2 = input + 1 */
-	val = bpf_map__fd(skel->maps.inner_map1);
-	bpf_map_update_elem(bpf_map__fd(skel->maps.outer_arr), &key, &val, 0);
-	val = bpf_map__fd(skel->maps.inner_map2);
-	bpf_map_update_elem(bpf_map__fd(skel->maps.outer_hash), &key, &val, 0);
+	map1_fd = bpf_map__fd(skel->maps.inner_map1);
+	bpf_map_update_elem(outer_arr_fd, &key, &map1_fd, 0);
+	map2_fd = bpf_map__fd(skel->maps.inner_map2);
+	bpf_map_update_elem(outer_hash_fd, &key, &map2_fd, 0);
 	skel->bss->input = 1;
 	usleep(1);
 
-	bpf_map_lookup_elem(bpf_map__fd(skel->maps.inner_map1), &key, &val);
+	bpf_map_lookup_elem(map1_fd, &key, &val);
 	CHECK(val != 1, "inner1", "got %d != exp %d\n", val, 1);
-	bpf_map_lookup_elem(bpf_map__fd(skel->maps.inner_map2), &key, &val);
+	bpf_map_lookup_elem(map2_fd, &key, &val);
 	CHECK(val != 2, "inner2", "got %d != exp %d\n", val, 2);
 
 	/* inner1 = input + 1, inner2 = input */
-	val = bpf_map__fd(skel->maps.inner_map2);
-	bpf_map_update_elem(bpf_map__fd(skel->maps.outer_arr), &key, &val, 0);
-	val = bpf_map__fd(skel->maps.inner_map1);
-	bpf_map_update_elem(bpf_map__fd(skel->maps.outer_hash), &key, &val, 0);
+	bpf_map_update_elem(outer_arr_fd, &key, &map2_fd, 0);
+	bpf_map_update_elem(outer_hash_fd, &key, &map1_fd, 0);
 	skel->bss->input = 3;
 	usleep(1);
 
-	bpf_map_lookup_elem(bpf_map__fd(skel->maps.inner_map1), &key, &val);
+	bpf_map_lookup_elem(map1_fd, &key, &val);
 	CHECK(val != 4, "inner1", "got %d != exp %d\n", val, 4);
-	bpf_map_lookup_elem(bpf_map__fd(skel->maps.inner_map2), &key, &val);
+	bpf_map_lookup_elem(map2_fd, &key, &val);
 	CHECK(val != 3, "inner2", "got %d != exp %d\n", val, 3);
 
+	for (i = 0; i < 5; i++) {
+		val = i % 2 ? map1_fd : map2_fd;
+		err = bpf_map_update_elem(outer_hash_fd, &key, &val, 0);
+		if (CHECK_FAIL(err)) {
+			printf("failed to update hash_of_maps on iter #%d\n", i);
+			goto cleanup;
+		}
+		err = bpf_map_update_elem(outer_arr_fd, &key, &val, 0);
+		if (CHECK_FAIL(err)) {
+			printf("failed to update hash_of_maps on iter #%d\n", i);
+			goto cleanup;
+		}
+	}
+
+	map1_id = bpf_map_id(skel->maps.inner_map1);
+	map2_id = bpf_map_id(skel->maps.inner_map2);
+	CHECK(map1_id == 0, "map1_id", "failed to get ID 1\n");
+	CHECK(map2_id == 0, "map2_id", "failed to get ID 2\n");
+
+	test_btf_map_in_map__destroy(skel);
+	skel = NULL;
+
+	/* we need to either wait for or force synchronize_rcu(), before
+	 * checking for "still exists" condition, otherwise map could still be
+	 * resolvable by ID, causing false positives.
+	 *
+	 * Older kernels (5.8 and earlier) freed map only after two
+	 * synchronize_rcu()s, so trigger two, to be entirely sure.
+	 */
+	CHECK(kern_sync_rcu(), "sync_rcu", "failed\n");
+	CHECK(kern_sync_rcu(), "sync_rcu", "failed\n");
+
+	fd = bpf_map_get_fd_by_id(map1_id);
+	if (CHECK(fd >= 0, "map1_leak", "inner_map1 leaked!\n")) {
+		close(fd);
+		goto cleanup;
+	}
+	fd = bpf_map_get_fd_by_id(map2_id);
+	if (CHECK(fd >= 0, "map2_leak", "inner_map2 leaked!\n")) {
+		close(fd);
+		goto cleanup;
+	}
+
 cleanup:
 	test_btf_map_in_map__destroy(skel);
 }

tools/testing/selftests/bpf/verifier/event_output.c

@@ -112,6 +112,7 @@
 	"perfevent for cgroup sockopt",
 	.insns =  { __PERF_EVENT_INSNS__ },
 	.prog_type = BPF_PROG_TYPE_CGROUP_SOCKOPT,
+	.expected_attach_type = BPF_CGROUP_SETSOCKOPT,
 	.fixup_map_event_output = { 4 },
 	.result = ACCEPT,
 	.retval = 1,