selftests/bpf: add test for bpf_msg_pop_data() overflow

Add a test in sockmap_basic.c that calls bpf_msg_pop_data() with a length
close to U32_MAX, which overflows the start + len bounds check. The sk_msg
program records the return value over a sendmsg and the test checks that
the call is rejected with -EINVAL.

Reviewed-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Cc: Jiayuan Chen <jiayuan.chen@linux.dev>
Signed-off-by: Sechang Lim <rhkrqnwk98@gmail.com>
Signed-off-by: Jiayuan Chen <jiayuan.chen@linux.dev>
Link: https://lore.kernel.org/r/20260615021959.140010-7-jiayuan.chen@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
index d2846579285f2e7707c864e3fe600414e203425d..cb3229711f93a36ab10652eda20617f5ecea4063 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
+++ b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
@@ -14,6 +14,7 @@
 #include "test_sockmap_pass_prog.skel.h"
 #include "test_sockmap_drop_prog.skel.h"
 #include "test_sockmap_change_tail.skel.h"
+#include "test_sockmap_msg_pop_data.skel.h"
 #include "bpf_iter_sockmap.skel.h"
 
 #include "sockmap_helpers.h"
@@ -666,6 +667,51 @@ out:
        test_sockmap_change_tail__destroy(skel);
 }
 
+static void test_sockmap_msg_verdict_pop_data(void)
+{
+       struct test_sockmap_msg_pop_data *skel;
+       int err, map, verdict;
+       int c1 = -1, p1 = -1, sent;
+       int zero = 0;
+       char *buf;
+       const size_t len = 32 * 1024;
+
+       skel = test_sockmap_msg_pop_data__open_and_load();
+       if (!ASSERT_OK_PTR(skel, "open_and_load"))
+               return;
+
+       verdict = bpf_program__fd(skel->progs.prog_msg_pop_data);
+       map = bpf_map__fd(skel->maps.sock_map);
+
+       err = bpf_prog_attach(verdict, map, BPF_SK_MSG_VERDICT, 0);
+       if (!ASSERT_OK(err, "bpf_prog_attach"))
+               goto out;
+
+       err = create_pair(AF_INET, SOCK_STREAM, &c1, &p1);
+       if (!ASSERT_OK(err, "create_pair"))
+               goto out;
+
+       err = bpf_map_update_elem(map, &zero, &c1, BPF_NOEXIST);
+       if (!ASSERT_OK(err, "bpf_map_update_elem"))
+               goto out_close;
+
+       buf = calloc(len, 1);
+       if (!ASSERT_OK_PTR(buf, "calloc"))
+               goto out_close;
+
+       sent = xsend(c1, buf, len, 0);
+       ASSERT_EQ(sent, (ssize_t)len, "xsend");
+       ASSERT_EQ(skel->data->pop_data_ret, -EINVAL, "pop_data_rejects overflow");
+
+       free(buf);
+
+out_close:
+       close(c1);
+       close(p1);
+out:
+       test_sockmap_msg_pop_data__destroy(skel);
+}
+
 static void test_sockmap_skb_verdict_peek_helper(int map)
 {
        int err, c1, p1, zero = 0, sent, recvd, avail;
@@ -1373,6 +1419,8 @@ void test_sockmap_basic(void)
                test_sockmap_skb_verdict_fionread(false);
        if (test__start_subtest("sockmap skb_verdict change tail"))
                test_sockmap_skb_verdict_change_tail();
+       if (test__start_subtest("sockmap msg_verdict pop_data overflow"))
+               test_sockmap_msg_verdict_pop_data();
        if (test__start_subtest("sockmap skb_verdict msg_f_peek"))
                test_sockmap_skb_verdict_peek();
        if (test__start_subtest("sockmap skb_verdict msg_f_peek with link"))

diff --git a/tools/testing/selftests/bpf/progs/test_sockmap_msg_pop_data.c b/tools/testing/selftests/bpf/progs/test_sockmap_msg_pop_data.c
new file mode 100644 (file)
index 0000000..301e65b
--- /dev/null
+++ b/tools/testing/selftests/bpf/progs/test_sockmap_msg_pop_data.c
@@ -0,0 +1,27 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+struct {
+       __uint(type, BPF_MAP_TYPE_SOCKMAP);
+       __uint(max_entries, 1);
+       __type(key, int);
+       __type(value, int);
+} sock_map SEC(".maps");
+
+#define POP_START 0x48a3
+#define POP_LEN   0xfffffffd
+
+long pop_data_ret = 1;
+
+SEC("sk_msg")
+int prog_msg_pop_data(struct sk_msg_md *msg)
+{
+       if (msg->size <= POP_START)
+               return SK_PASS;
+
+       pop_data_ret = bpf_msg_pop_data(msg, POP_START, POP_LEN, 0);
+       return SK_PASS;
+}
+
+char _license[] SEC("license") = "GPL";