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charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ltp-bounces+ltp=archiver.kernel.org@lists.linux.it Sender: "ltp" Hi! > Verify that an unprivileged process may enter failfs when it > committed to no_new_privs, since setuid binaries then pose no > confused deputy risk anymore. The test also verifies that a process > which entered failfs counts as chrooted: it can no longer create a > user namespace with unshare() to regain CAP_SYS_CHROOT. > > Signed-off-by: Andrea Cervesato > --- > runtest/staging | 1 + > testcases/kernel/syscalls/fchroot/.gitignore | 1 + > testcases/kernel/syscalls/fchroot/fchroot11.c | 70 +++++++++++++++++++++++++++ > 3 files changed, 72 insertions(+) > > diff --git a/runtest/staging b/runtest/staging > index 9ec2a7897..137e3f99a 100644 > --- a/runtest/staging > +++ b/runtest/staging > @@ -10,3 +10,4 @@ fchroot07 fchroot07 > fchroot08 fchroot08 > fchroot09 fchroot09 > fchroot10 fchroot10 > +fchroot11 fchroot11 > diff --git a/testcases/kernel/syscalls/fchroot/.gitignore b/testcases/kernel/syscalls/fchroot/.gitignore > index 53a1fa1d0..650ef2690 100644 > --- a/testcases/kernel/syscalls/fchroot/.gitignore > +++ b/testcases/kernel/syscalls/fchroot/.gitignore > @@ -9,3 +9,4 @@ fchroot07_child > fchroot08 > fchroot09 > fchroot10 > +fchroot11 > diff --git a/testcases/kernel/syscalls/fchroot/fchroot11.c b/testcases/kernel/syscalls/fchroot/fchroot11.c > new file mode 100644 > index 000000000..85401e5fe > --- /dev/null > +++ b/testcases/kernel/syscalls/fchroot/fchroot11.c > @@ -0,0 +1,70 @@ > +// SPDX-License-Identifier: GPL-2.0-or-later > +/* > + * Copyright (C) 2026 SUSE LLC Andrea Cervesato > + */ > + > +/*\ > + * Test unprivileged :manpage:`fchroot(2)` into failfs with no_new_privs > + * set. > + * > + * An unprivileged process may enter failfs when it committed to > + * no_new_privs, since setuid binaries then pose no confused deputy risk > + * anymore. The test also verifies that a process which entered failfs > + * counts as chrooted: it can no longer create a user namespace with > + * :manpage:`unshare(2)` to regain ``CAP_SYS_CHROOT``. > + * > + * The user namespace check requires ``CONFIG_USER_NS``, which is enforced > + * with ``.needs_kconfigs``. > + * > + * Root is required to drop to an unprivileged user in the forked child. > + */ > + > +#define _GNU_SOURCE > +#include > +#include > +#include > +#include "tst_test.h" > +#include "lapi/fcntl.h" > +#include "lapi/prctl.h" > +#include "lapi/sched.h" > +#include "lapi/syscalls.h" > + > +static struct passwd *ltpuser; > + > +static void run(void) > +{ > + if (SAFE_FORK()) > + return; > + > + SAFE_SETRESUID(ltpuser->pw_uid, ltpuser->pw_uid, > + ltpuser->pw_uid); > + > + SAFE_PRCTL(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); > + > + TST_EXP_PASS(tst_syscall(__NR_fchroot, FD_FAILFS_ROOT, 0), > + "unprivileged fchroot() with no_new_privs"); > + > + TST_EXP_FAIL2(open("/etc/passwd", O_RDONLY), EOPNOTSUPP, > + "absolute lookup after entering failfs"); AFAIK there is no /etc/passwd on Android. Maybe we should use /dev/zero instead? > + TST_EXP_FAIL(unshare(CLONE_NEWUSER), EPERM, > + "user namespace creation blocked by the failfs root"); > + > + exit(0); Here as well, no need for the exit(0). > +} > + > +static void setup(void) > +{ > + ltpuser = SAFE_GETPWNAM("nobody"); > +} > + > +static struct tst_test test = { > + .setup = setup, > + .test_all = run, > + .needs_root = 1, > + .forks_child = 1, > + .needs_kconfigs = (const char *[]) { > + "CONFIG_USER_NS=y", > + NULL, > + } > +}; > > -- > 2.51.0 > > > -- > Mailing list info: https://lists.linux.it/listinfo/ltp -- Cyril Hrubis chrubis@suse.cz -- Mailing list info: https://lists.linux.it/listinfo/ltp