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selftests/ovl: add third selftest for "override_creds"

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Add a simple test to verify that the new "override_creds" option works.

Link: https://lore.kernel.org/r/20250219-work-overlayfs-v3-4-46af55e4ceda@kernel.org
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Christian Brauner 2025-02-19 11:01:52 +01:00
parent 6e5ed6587e
commit a1579f6bf6
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
3 changed files with 108 additions and 0 deletions
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80
tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c
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@ -8,6 +8,7 @@
#include <string.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/sysmacros.h>
#include <sys/mount.h>
#include <unistd.h>
@ -442,4 +443,83 @@ TEST_F(set_layers_via_fds, set_override_creds_invalid)
ASSERT_EQ(close(fd_userns2), 0);
}
TEST_F(set_layers_via_fds, set_override_creds_nomknod)
{
int fd_context, fd_tmpfs, fd_overlay;
int layer_fds[] = { [0 ... 3] = -EBADF };
pid_t pid;
int pidfd;
ASSERT_EQ(unshare(CLONE_NEWNS), 0);
ASSERT_EQ(sys_mount(NULL, "/", NULL, MS_SLAVE | MS_REC, NULL), 0);
fd_context = sys_fsopen("tmpfs", 0);
ASSERT_GE(fd_context, 0);
ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_CMD_CREATE, NULL, NULL, 0), 0);
fd_tmpfs = sys_fsmount(fd_context, 0, 0);
ASSERT_GE(fd_tmpfs, 0);
ASSERT_EQ(close(fd_context), 0);
ASSERT_EQ(mkdirat(fd_tmpfs, "w", 0755), 0);
ASSERT_EQ(mkdirat(fd_tmpfs, "u", 0755), 0);
ASSERT_EQ(mkdirat(fd_tmpfs, "l1", 0755), 0);
ASSERT_EQ(mkdirat(fd_tmpfs, "l2", 0755), 0);
layer_fds[0] = openat(fd_tmpfs, "w", O_DIRECTORY);
ASSERT_GE(layer_fds[0], 0);
layer_fds[1] = openat(fd_tmpfs, "u", O_DIRECTORY);
ASSERT_GE(layer_fds[1], 0);
layer_fds[2] = openat(fd_tmpfs, "l1", O_DIRECTORY);
ASSERT_GE(layer_fds[2], 0);
layer_fds[3] = openat(fd_tmpfs, "l2", O_DIRECTORY);
ASSERT_GE(layer_fds[3], 0);
ASSERT_EQ(sys_move_mount(fd_tmpfs, "", -EBADF, "/tmp", MOVE_MOUNT_F_EMPTY_PATH), 0);
ASSERT_EQ(close(fd_tmpfs), 0);
fd_context = sys_fsopen("overlay", 0);
ASSERT_GE(fd_context, 0);
ASSERT_NE(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir", NULL, layer_fds[2]), 0);
ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "workdir", NULL, layer_fds[0]), 0);
ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "upperdir", NULL, layer_fds[1]), 0);
ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[2]), 0);
ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FD, "lowerdir+", NULL, layer_fds[3]), 0);
ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_SET_FLAG, "userxattr", NULL, 0), 0);
pid = create_child(&pidfd, 0);
ASSERT_GE(pid, 0);
if (pid == 0) {
if (!cap_down(CAP_MKNOD))
_exit(EXIT_FAILURE);
if (!cap_down(CAP_SYS_ADMIN))
_exit(EXIT_FAILURE);
if (sys_fsconfig(fd_context, FSCONFIG_SET_FLAG, "override_creds", NULL, 0))
_exit(EXIT_FAILURE);
_exit(EXIT_SUCCESS);
}
ASSERT_EQ(sys_waitid(P_PID, pid, NULL, WEXITED), 0);
ASSERT_GE(close(pidfd), 0);
ASSERT_EQ(sys_fsconfig(fd_context, FSCONFIG_CMD_CREATE, NULL, NULL, 0), 0);
fd_overlay = sys_fsmount(fd_context, 0, 0);
ASSERT_GE(fd_overlay, 0);
ASSERT_EQ(sys_move_mount(fd_overlay, "", -EBADF, "/set_layers_via_fds", MOVE_MOUNT_F_EMPTY_PATH), 0);
ASSERT_EQ(mknodat(fd_overlay, "dev-zero", S_IFCHR | 0644, makedev(1, 5)), -1);
ASSERT_EQ(errno, EPERM);
ASSERT_EQ(close(fd_context), 0);
ASSERT_EQ(close(fd_overlay), 0);
}
TEST_HARNESS_MAIN

27
tools/testing/selftests/filesystems/utils.c
View File

@ -472,3 +472,30 @@ int caps_down(void)
cap_free(caps);
return fret;
}
/* cap_down - lower an effective cap */
int cap_down(cap_value_t down)
{
bool fret = false;
cap_t caps = NULL;
cap_value_t cap = down;
int ret = -1;
caps = cap_get_proc();
if (!caps)
goto out;
ret = cap_set_flag(caps, CAP_EFFECTIVE, 1, &cap, 0);
if (ret)
goto out;
ret = cap_set_proc(caps);
if (ret)
goto out;
fret = true;
out:
cap_free(caps);
return fret;
}

1
tools/testing/selftests/filesystems/utils.h
View File

@ -24,6 +24,7 @@ extern int get_userns_fd(unsigned long nsid, unsigned long hostid,
unsigned long range);
extern int caps_down(void);
extern int cap_down(cap_value_t down);
extern bool switch_ids(uid_t uid, gid_t gid);