openat_tmpfile_supported() in the idmapped mount tests probes O_TMPFILE on the idmapped mount (open_tree_fd) as the test's fsuid -- but that fsuid is not mapped by the idmapped mount under test, so it really asks "can this unmapped caller create a tmpfile through this idmap?" instead of "does the filesystem support O_TMPFILE?". On overlayfs this is a false negative: the backing tmpfile ends up owned by an unmapped id, overlayfs opens it with O_NOATIME and may_open() returns -EPERM, so the tmpfile sub-tests are wrongly skipped. O_TMPFILE support is a property of the filesystem, not of the idmapped mount or the caller's mapping. Probe info->t_dir1_fd, the base mount that the caller owns, exactly as the non-idmapped setgid tests already do. The probe then succeeds on every filesystem and the tmpfile sub-tests run as the mapped fsuid. Signed-off-by: Christian Brauner (Amutable) --- src/vfs/idmapped-mounts.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/src/vfs/idmapped-mounts.c b/src/vfs/idmapped-mounts.c index ed9992f9..8f8441c9 100644 --- a/src/vfs/idmapped-mounts.c +++ b/src/vfs/idmapped-mounts.c @@ -3838,7 +3838,7 @@ int tcore_setgid_create_idmapped(const struct vfstest_info *info) goto out; } - supported = openat_tmpfile_supported(open_tree_fd); + supported = openat_tmpfile_supported(info->t_dir1_fd); pid = fork(); if (pid < 0) { @@ -4014,7 +4014,7 @@ int tcore_setgid_create_idmapped_in_userns(const struct vfstest_info *info) goto out; } - supported = openat_tmpfile_supported(open_tree_fd); + supported = openat_tmpfile_supported(info->t_dir1_fd); pid = fork(); if (pid < 0) { @@ -7733,7 +7733,7 @@ static int setgid_create_umask_idmapped(const struct vfstest_info *info) goto out; } - supported = openat_tmpfile_supported(open_tree_fd); + supported = openat_tmpfile_supported(info->t_dir1_fd); pid = fork(); if (pid < 0) { @@ -7947,7 +7947,7 @@ static int setgid_create_umask_idmapped_in_userns(const struct vfstest_info *inf goto out; } - supported = openat_tmpfile_supported(open_tree_fd); + supported = openat_tmpfile_supported(info->t_dir1_fd); /* * Below we verify that setgid inheritance for a newly created file or @@ -8181,7 +8181,7 @@ static int setgid_create_acl_idmapped(const struct vfstest_info *info) goto out; } - supported = openat_tmpfile_supported(open_tree_fd); + supported = openat_tmpfile_supported(info->t_dir1_fd); pid = fork(); if (pid < 0) { @@ -8536,7 +8536,7 @@ static int setgid_create_acl_idmapped_in_userns(const struct vfstest_info *info) goto out; } - supported = openat_tmpfile_supported(open_tree_fd); + supported = openat_tmpfile_supported(info->t_dir1_fd); /* * Below we verify that setgid inheritance for a newly created file or -- 2.47.3