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RCVD_VIA_SMTP_AUTH(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FROM_EQ_ENVFROM(0.00)[]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_TWO(0.00)[2]; RCVD_COUNT_TWO(0.00)[2]; TO_MATCH_ENVRCPT_ALL(0.00)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.com:email,suse.com:mid,imap1.dmz-prg2.suse.org:helo,imap1.dmz-prg2.suse.org:rdns]; TO_DN_ALL(0.00)[]; DKIM_TRACE(0.00)[suse.de:+] X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Virus-Scanned: clamav-milter 1.0.9 at in-2.smtp.seeweb.it X-Virus-Status: Clean Subject: [LTP] [PATCH STAGING 12/16] fchroot09: test setns escape from failfs root X-BeenThere: ltp@lists.linux.it X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux Test Project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ltp-bounces+ltp=archiver.kernel.org@lists.linux.it Sender: "ltp" From: Andrea Cervesato Verify that entering failfs with fchroot() is hard to undo: a process inside counts as chrooted, so the remaining way out is a pre-opened mount namespace fd. setns() into it resets both the root and the working directory. Signed-off-by: Andrea Cervesato --- runtest/staging | 1 + testcases/kernel/syscalls/fchroot/.gitignore | 1 + testcases/kernel/syscalls/fchroot/fchroot09.c | 70 +++++++++++++++++++++++++++ 3 files changed, 72 insertions(+) diff --git a/runtest/staging b/runtest/staging index 8dfe95c4a..23f6c6a20 100644 --- a/runtest/staging +++ b/runtest/staging @@ -8,3 +8,4 @@ fchroot05 fchroot05 fchroot06 fchroot06 fchroot07 fchroot07 fchroot08 fchroot08 +fchroot09 fchroot09 diff --git a/testcases/kernel/syscalls/fchroot/.gitignore b/testcases/kernel/syscalls/fchroot/.gitignore index c099b4b3a..e803fa2b7 100644 --- a/testcases/kernel/syscalls/fchroot/.gitignore +++ b/testcases/kernel/syscalls/fchroot/.gitignore @@ -6,3 +6,4 @@ fchroot05 fchroot06 fchroot07 fchroot08 +fchroot09 diff --git a/testcases/kernel/syscalls/fchroot/fchroot09.c b/testcases/kernel/syscalls/fchroot/fchroot09.c new file mode 100644 index 000000000..196a6844d --- /dev/null +++ b/testcases/kernel/syscalls/fchroot/fchroot09.c @@ -0,0 +1,70 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2026 SUSE LLC Andrea Cervesato + */ + +/*\ + * Test that :manpage:`setns(2)` escapes the failfs root. + * + * Entering failfs with :manpage:`fchroot(2)` is hard to undo: a process + * inside counts as chrooted, so :manpage:`chroot(2)` and fchroot() back + * out require CAP_SYS_CHROOT. The remaining way out is a pre-opened mount + * namespace file descriptor: setns() into it resets both the root and the + * working directory. + * + * Root is required because entering failfs requires CAP_SYS_CHROOT and + * :manpage:`setns(2)` into the mount namespace requires CAP_SYS_ADMIN. + * + * The test runs in a forked child so the root of the parent process is + * left untouched. + */ + +#define _GNU_SOURCE +#include +#include +#include "tst_test.h" +#include "lapi/fcntl.h" +#include "lapi/sched.h" +#include "lapi/setns.h" +#include "lapi/syscalls.h" + +static void run(void) +{ + if (!SAFE_FORK()) { + struct stat realroot, realcwd, st; + int nsfd; + + SAFE_STAT("/", &realroot); + SAFE_STAT(".", &realcwd); + nsfd = SAFE_OPEN("/proc/self/ns/mnt", O_RDONLY); + + TST_EXP_PASS(tst_syscall(__NR_fchroot, FD_FAILFS_ROOT, 0), + "fchroot() with the FD_FAILFS_ROOT sentinel"); + + TST_EXP_FAIL2(open("/etc", O_PATH), EOPNOTSUPP, + "absolute lookup after entering failfs"); + + TST_EXP_PASS(setns(nsfd, CLONE_NEWNS), + "setns() back into the mount namespace"); + + SAFE_CLOSE(nsfd); + + SAFE_STAT("/", &st); + TST_EXP_EXPR(st.st_dev == realroot.st_dev && + st.st_ino == realroot.st_ino, + "root restored after setns()"); + + SAFE_STAT(".", &st); + TST_EXP_EXPR(st.st_dev == realcwd.st_dev && + st.st_ino == realcwd.st_ino, + "working directory restored after setns()"); + + exit(0); + } +} + +static struct tst_test test = { + .test_all = run, + .needs_root = 1, + .forks_child = 1, +}; -- 2.51.0 -- Mailing list info: https://lists.linux.it/listinfo/ltp