selftests/bpf: Test RENAME_EXCHANGE and RENAME_NOREPLACE on bpffs

Add tests to exercise the behaviour of RENAME_EXCHANGE and RENAME_NOREPLACE
on bpffs. The former checks that after an exchange the inode of two
directories has changed. The latter checks that the source still exists
after a failed rename. Generally, having support for renameat2(RENAME_EXCHANGE)
in bpffs fixes atomic upgrades of our sk_lookup control plane.

Signed-off-by: Lorenz Bauer <lmb@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211028094724.59043-5-lmb@cloudflare.com

diff --git a/tools/testing/selftests/bpf/prog_tests/test_bpffs.c b/tools/testing/selftests/bpf/prog_tests/test_bpffs.c
index 533e3f3..d29ebfe 100644 (file)
--- a/tools/testing/selftests/bpf/prog_tests/test_bpffs.c
+++ b/tools/testing/selftests/bpf/prog_tests/test_bpffs.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 /* Copyright (c) 2020 Facebook */
 #define _GNU_SOURCE
+#include <stdio.h>
 #include <sched.h>
 #include <sys/mount.h>
 #include <sys/stat.h>
@@ -29,7 +30,8 @@ static int read_iter(char *file)
 
 static int fn(void)
 {
-       int err;
+       struct stat a, b, c;
+       int err, map;
 
        err = unshare(CLONE_NEWNS);
        if (!ASSERT_OK(err, "unshare"))
@@ -67,6 +69,67 @@ static int fn(void)
        err = read_iter(TDIR "/fs2/progs.debug");
        if (!ASSERT_OK(err, "reading " TDIR "/fs2/progs.debug"))
                goto out;
+
+       err = mkdir(TDIR "/fs1/a", 0777);
+       if (!ASSERT_OK(err, "creating " TDIR "/fs1/a"))
+               goto out;
+       err = mkdir(TDIR "/fs1/a/1", 0777);
+       if (!ASSERT_OK(err, "creating " TDIR "/fs1/a/1"))
+               goto out;
+       err = mkdir(TDIR "/fs1/b", 0777);
+       if (!ASSERT_OK(err, "creating " TDIR "/fs1/b"))
+               goto out;
+
+       map = bpf_create_map(BPF_MAP_TYPE_ARRAY, 4, 4, 1, 0);
+       if (!ASSERT_GT(map, 0, "create_map(ARRAY)"))
+               goto out;
+       err = bpf_obj_pin(map, TDIR "/fs1/c");
+       if (!ASSERT_OK(err, "pin map"))
+               goto out;
+       close(map);
+
+       /* Check that RENAME_EXCHANGE works for directories. */
+       err = stat(TDIR "/fs1/a", &a);
+       if (!ASSERT_OK(err, "stat(" TDIR "/fs1/a)"))
+               goto out;
+       err = renameat2(0, TDIR "/fs1/a", 0, TDIR "/fs1/b", RENAME_EXCHANGE);
+       if (!ASSERT_OK(err, "renameat2(/fs1/a, /fs1/b, RENAME_EXCHANGE)"))
+               goto out;
+       err = stat(TDIR "/fs1/b", &b);
+       if (!ASSERT_OK(err, "stat(" TDIR "/fs1/b)"))
+               goto out;
+       if (!ASSERT_EQ(a.st_ino, b.st_ino, "b should have a's inode"))
+               goto out;
+       err = access(TDIR "/fs1/b/1", F_OK);
+       if (!ASSERT_OK(err, "access(" TDIR "/fs1/b/1)"))
+               goto out;
+
+       /* Check that RENAME_EXCHANGE works for mixed file types. */
+       err = stat(TDIR "/fs1/c", &c);
+       if (!ASSERT_OK(err, "stat(" TDIR "/fs1/map)"))
+               goto out;
+       err = renameat2(0, TDIR "/fs1/c", 0, TDIR "/fs1/b", RENAME_EXCHANGE);
+       if (!ASSERT_OK(err, "renameat2(/fs1/c, /fs1/b, RENAME_EXCHANGE)"))
+               goto out;
+       err = stat(TDIR "/fs1/b", &b);
+       if (!ASSERT_OK(err, "stat(" TDIR "/fs1/b)"))
+               goto out;
+       if (!ASSERT_EQ(c.st_ino, b.st_ino, "b should have c's inode"))
+               goto out;
+       err = access(TDIR "/fs1/c/1", F_OK);
+       if (!ASSERT_OK(err, "access(" TDIR "/fs1/c/1)"))
+               goto out;
+
+       /* Check that RENAME_NOREPLACE works. */
+       err = renameat2(0, TDIR "/fs1/b", 0, TDIR "/fs1/a", RENAME_NOREPLACE);
+       if (!ASSERT_ERR(err, "renameat2(RENAME_NOREPLACE)")) {
+               err = -EINVAL;
+               goto out;
+       }
+       err = access(TDIR "/fs1/b", F_OK);
+       if (!ASSERT_OK(err, "access(" TDIR "/fs1/b)"))
+               goto out;
+
 out:
        umount(TDIR "/fs1");
        umount(TDIR "/fs2");