From: Christian Brauner <christian.brauner@xxxxxxxxxx>
Add a test to verify that setting a v3 fscap from an idmapped mount
works as expected. This and other related use-cases were regressed by
commit [1] which was reverted in [2] and the proper fix merged right
before v5.12 was released in [3].
[1]: commit 3b0c2d3eaa83 ("Revert 95ebabde382c ("capabilities: Don't allow writing ambiguous v3 file capabilities")")
[2]: commit 95ebabde382c ("capabilities: Don't allow writing ambiguous v3 file capabilities")
[3]: commit db2e718a4798 ("capabilities: require CAP_SETFCAP to map uid 0")
Cc: fstests@xxxxxxxxxxxxxxx
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Christian Brauner <christian.brauner@xxxxxxxxxx>
---
src/idmapped-mounts/idmapped-mounts.c | 118 +++++++++++++++++++++++++-
1 file changed, 117 insertions(+), 1 deletion(-)
diff --git a/src/idmapped-mounts/idmapped-mounts.c b/src/idmapped-mounts/idmapped-mounts.c
index 870a8fe7..6582f3a2 100644
--- a/src/idmapped-mounts/idmapped-mounts.c
+++ b/src/idmapped-mounts/idmapped-mounts.c
@@ -3204,6 +3204,121 @@ out:
return fret;
}
+static int fscaps_idmapped_mounts_in_userns_valid_in_ancestor_userns(void)
+{
+ int fret = -1;
+ int file1_fd = -EBADF, file1_fd2 = -EBADF, open_tree_fd = -EBADF;
+ struct mount_attr attr = {
+ .attr_set = MOUNT_ATTR_IDMAP,
+ };
+ pid_t pid;
+
+ file1_fd = openat(t_dir1_fd, FILE1, O_CREAT | O_EXCL | O_CLOEXEC, 0644);
+ if (file1_fd < 0) {
+ log_stderr("failure: openat");
+ goto out;
+ }
+
+ /* Skip if vfs caps are unsupported. */
+ if (set_dummy_vfs_caps(file1_fd, 0, 1000))
+ return 0;
+
+ if (fremovexattr(file1_fd, "security.capability")) {
+ log_stderr("failure: fremovexattr");
+ goto out;
+ }
+ if (expected_dummy_vfs_caps_uid(file1_fd, -1)) {
+ log_stderr("failure: expected_dummy_vfs_caps_uid");
+ goto out;
+ }
+ if (errno != ENODATA) {
+ log_stderr("failure: errno");
+ goto out;
+ }
+
+ /* Changing mount properties on a detached mount. */
+ attr.userns_fd = get_userns_fd(0, 10000, 10000);
+ if (attr.userns_fd < 0) {
+ log_stderr("failure: get_userns_fd");
+ goto out;
+ }
+
+ open_tree_fd = sys_open_tree(t_dir1_fd, "",
+ AT_EMPTY_PATH |
+ AT_NO_AUTOMOUNT |
+ AT_SYMLINK_NOFOLLOW |
+ OPEN_TREE_CLOEXEC |
+ OPEN_TREE_CLONE);
+ if (open_tree_fd < 0) {
+ log_stderr("failure: sys_open_tree");
+ goto out;
+ }
+
+ if (sys_mount_setattr(open_tree_fd, "", AT_EMPTY_PATH, &attr, sizeof(attr))) {
+ log_stderr("failure: sys_mount_setattr");
+ goto out;
+ }
+
+ file1_fd2 = openat(open_tree_fd, FILE1, O_RDWR | O_CLOEXEC, 0);
+ if (file1_fd2 < 0) {
+ log_stderr("failure: openat");
+ goto out;
+ }
+
+ /*
+ * Verify we can set an v3 fscap for real root this was regressed at
+ * some point. Make sure this doesn't happen again!
+ */
+ pid = fork();
+ if (pid < 0) {
+ log_stderr("failure: fork");
+ goto out;
+ }
+ if (pid == 0) {
+ if (!switch_userns(attr.userns_fd, 0, 0, false))
+ die("failure: switch_userns");
+
+ if (expected_dummy_vfs_caps_uid(file1_fd2, -1))
+ die("failure: expected_dummy_vfs_caps_uid");
+ if (errno != ENODATA)
+ die("failure: errno");
+
+ if (set_dummy_vfs_caps(file1_fd2, 0, 0))
+ die("failure: set_dummy_vfs_caps");
+
+ if (!expected_dummy_vfs_caps_uid(file1_fd2, 0))
+ die("failure: expected_dummy_vfs_caps_uid");
+
+ if (!expected_dummy_vfs_caps_uid(file1_fd, 0) && errno != EOVERFLOW)
+ die("failure: expected_dummy_vfs_caps_uid");
+
+ exit(EXIT_SUCCESS);
+ }
+
+ if (wait_for_pid(pid))
+ goto out;
+
+ if (!expected_dummy_vfs_caps_uid(file1_fd2, 10000)) {
+ log_stderr("failure: expected_dummy_vfs_caps_uid");
+ goto out;
+ }
+
+ if (!expected_dummy_vfs_caps_uid(file1_fd, 0)) {
+ log_stderr("failure: expected_dummy_vfs_caps_uid");
+ goto out;
+ }
+
+ fret = 0;
+ log_debug("Ran test");
+out:
+ safe_close(attr.userns_fd);
+ safe_close(file1_fd);
+ safe_close(file1_fd2);
+ safe_close(open_tree_fd);
+
+ return fret;
+}
+
static int fscaps_idmapped_mounts_in_userns_separate_userns(void)
{
int fret = -1;
@@ -8748,7 +8863,8 @@ struct t_idmapped_mounts {
{ fscaps, "fscaps on regular mounts", },
{ fscaps_idmapped_mounts, "fscaps on idmapped mounts", },
{ fscaps_idmapped_mounts_in_userns, "fscaps on idmapped mounts in user namespace", },
- { fscaps_idmapped_mounts_in_userns_separate_userns, "fscaps on idmapped mounts in user namespace with different id mappings ", },
+ { fscaps_idmapped_mounts_in_userns_separate_userns, "fscaps on idmapped mounts in user namespace with different id mappings", },
+ { fscaps_idmapped_mounts_in_userns_valid_in_ancestor_userns, "fscaps on idmapped mounts in user namespace writing fscap valid in ancestor userns", },
{ fsids_mapped, "mapped fsids", },
{ fsids_unmapped, "unmapped fsids", },
{ hardlink_crossing_mounts, "cross mount hardlink", },
base-commit: 15510d3a208187e234333f7974580786d54d52dc
--
2.27.0
