| Message ID | 20250219-work-overlayfs-v3-4-46af55e4ceda@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | ovl: add override_creds mount option | expand |
On Wed, Feb 19, 2025 at 11:02 AM Christian Brauner <brauner@kernel.org> wrote: > > Add a simple test to verify that the new "override_creds" option works. > > Signed-off-by: Christian Brauner <brauner@kernel.org> Reviewed-by: Amir Goldstein <amir73il@gmail.com> > --- > .../filesystems/overlayfs/set_layers_via_fds.c | 80 ++++++++++++++++++++++ > tools/testing/selftests/filesystems/utils.c | 27 ++++++++ > tools/testing/selftests/filesystems/utils.h | 1 + > 3 files changed, 108 insertions(+) > > diff --git a/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c b/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c > index 6b65e3610578..fd1e5d7c13a3 100644 > --- a/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c > +++ b/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c > @@ -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 > diff --git a/tools/testing/selftests/filesystems/utils.c b/tools/testing/selftests/filesystems/utils.c > index 0e8080bd0aea..e553c89c5b19 100644 > --- a/tools/testing/selftests/filesystems/utils.c > +++ b/tools/testing/selftests/filesystems/utils.c > @@ -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; > +} > diff --git a/tools/testing/selftests/filesystems/utils.h b/tools/testing/selftests/filesystems/utils.h > index f35001a75f99..7f1df2a3e94c 100644 > --- a/tools/testing/selftests/filesystems/utils.h > +++ b/tools/testing/selftests/filesystems/utils.h > @@ -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); > > > -- > 2.47.2 >
diff --git a/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c b/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c index 6b65e3610578..fd1e5d7c13a3 100644 --- a/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c +++ b/tools/testing/selftests/filesystems/overlayfs/set_layers_via_fds.c @@ -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 diff --git a/tools/testing/selftests/filesystems/utils.c b/tools/testing/selftests/filesystems/utils.c index 0e8080bd0aea..e553c89c5b19 100644 --- a/tools/testing/selftests/filesystems/utils.c +++ b/tools/testing/selftests/filesystems/utils.c @@ -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; +} diff --git a/tools/testing/selftests/filesystems/utils.h b/tools/testing/selftests/filesystems/utils.h index f35001a75f99..7f1df2a3e94c 100644 --- a/tools/testing/selftests/filesystems/utils.h +++ b/tools/testing/selftests/filesystems/utils.h @@ -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);
Add a simple test to verify that the new "override_creds" option works. Signed-off-by: Christian Brauner <brauner@kernel.org> --- .../filesystems/overlayfs/set_layers_via_fds.c | 80 ++++++++++++++++++++++ tools/testing/selftests/filesystems/utils.c | 27 ++++++++ tools/testing/selftests/filesystems/utils.h | 1 + 3 files changed, 108 insertions(+)