Re: [PATCH v3 RESEND] selftests: filesystems: Add functional test for the abort file in fusectl

[Miklos Szeredi <miklos@szeredi.hu>]

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On Tue, 10 Jun 2025 at 04:10, Chen Linxuan <chenlinxuan@uniontech.com> wrote:
>
> This patch add a simple functional test for the "abort" file
> in fusectlfs (/sys/fs/fuse/connections/ID/about).
>
> A simple fuse daemon is added for testing.
>
> Related discussion can be found in the link below.
>
> Link: https://lore.kernel.org/all/CAOQ4uxjKFXOKQxPpxtS6G_nR0tpw95w0GiO68UcWg_OBhmSY=Q@mail.gmail.com/
> Signed-off-by: Chen Linxuan <chenlinxuan@uniontech.com>
> Acked-by: Shuah Khan <skhan@linuxfoundation.org>
> Reviewed-by: Amir Goldstein <amir73il@gmail.com>

Thanks.

I suggest setting up a userns environment, see attached patch (also
fixes a EBUSY on umount/rmdir).

Thanks,
Miklos

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diff --git a/tools/testing/selftests/filesystems/fuse/fusectl_test.c b/tools/testing/selftests/filesystems/fuse/fusectl_test.c
index 7050fbe0970e..8d124d1cacb2 100644
--- a/tools/testing/selftests/filesystems/fuse/fusectl_test.c
+++ b/tools/testing/selftests/filesystems/fuse/fusectl_test.c
@@ -14,6 +14,7 @@
 #include <sys/wait.h>
 #include <unistd.h>
 #include <dirent.h>
+#include <sched.h>
 #include <linux/limits.h>
 
 #include "../../kselftest_harness.h"
@@ -23,6 +24,17 @@
 #define FUSE_DEVICE "/dev/fuse"
 #define FUSECTL_TEST_VALUE "1"
 
+static void write_file(struct __test_metadata *const _metadata,
+		       const char *path, const char *val)
+{
+	int fd = open(path, O_WRONLY);
+	size_t len = strlen(val);
+
+	ASSERT_GE(fd, 0);
+	ASSERT_EQ(write(fd, val, len), len);
+	ASSERT_EQ(close(fd), 0);
+}
+
 FIXTURE(fusectl){
 	char fuse_mountpoint[sizeof(FUSE_MOUNTPOINT)];
 	int connection;
@@ -33,6 +45,18 @@ FIXTURE_SETUP(fusectl)
 	const char *fuse_mnt_prog = "./fuse_mnt";
 	int status, pid;
 	struct stat statbuf;
+	uid_t uid = getuid();
+	gid_t gid = getgid();
+	char buf[32];
+
+	/* Setup userns */
+	ASSERT_EQ(unshare(CLONE_NEWNS|CLONE_NEWUSER), 0);
+	sprintf(buf, "0 %d 1", uid);
+	write_file(_metadata, "/proc/self/uid_map", buf);
+	write_file(_metadata, "/proc/self/setgroups", "deny");
+	sprintf(buf, "0 %d 1", gid);
+	write_file(_metadata, "/proc/self/gid_map", buf);
+	ASSERT_EQ(mount("", "/", NULL, MS_REC|MS_PRIVATE, NULL), 0);
 
 	strcpy(self->fuse_mountpoint, FUSE_MOUNTPOINT);
 
@@ -73,7 +97,7 @@ FIXTURE_SETUP(fusectl)
 
 FIXTURE_TEARDOWN(fusectl)
 {
-	umount(self->fuse_mountpoint);
+	umount2(self->fuse_mountpoint, MNT_DETACH);
 	rmdir(self->fuse_mountpoint);
 }