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a=ed25519-sha256; t=1787174658; l=3948; i=andrea.cervesato@suse.com; s=20251210; h=from:subject:message-id; bh=G66iahwJA3fYX9+Pid9lOJ7vNUAlbZ75vO3oFavU+Ww=; b=x1gjJsxIJfV0DslcsagKpKVYrNeUD18Nt8rWptyXKCY5/nDVrcoJSjw/lSHtuv+q+P51TN5uF tgRkE80DAkfBvjpWEaYt/pCovmkzUwDXgfnLqfr7kWUGjo7K9Ewv+Pf X-Developer-Key: i=andrea.cervesato@suse.com; a=ed25519; pk=zKY+6GCauOiuHNZ//d8PQ/UL4jFCTKbXrzXAOQSLevI= X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCPT_COUNT_TWO(0.00)[2]; RCVD_TLS_ALL(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; ARC_NA(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; TO_DN_ALL(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; FROM_HAS_DN(0.00)[]; MIME_TRACE(0.00)[0:+]; FROM_EQ_ENVFROM(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[imap1.dmz-prg2.suse.org:helo, suse.com:mid, suse.com:email] X-Virus-Scanned: clamav-milter 1.0.9 at in-7.smtp.seeweb.it X-Virus-Status: Clean Subject: [LTP] [PATCH STAGING 09/16] fchroot06: test path walks under 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 once the root is in failfs only lookups anchored at a file descriptor keep working: relative lookups from the working directory and from a pre-opened directory fd succeed, absolute symlinks fail with EOPNOTSUPP and ".." walks clamp at the top of the mount tree, landing on the real root. Signed-off-by: Andrea Cervesato --- runtest/staging | 1 + testcases/kernel/syscalls/fchroot/.gitignore | 1 + testcases/kernel/syscalls/fchroot/fchroot06.c | 90 +++++++++++++++++++++++++++ 3 files changed, 92 insertions(+) diff --git a/runtest/staging b/runtest/staging index 49f51d637..8b6b1ecd9 100644 --- a/runtest/staging +++ b/runtest/staging @@ -5,3 +5,4 @@ fchroot02 fchroot02 fchroot03 fchroot03 fchroot04 fchroot04 fchroot05 fchroot05 +fchroot06 fchroot06 diff --git a/testcases/kernel/syscalls/fchroot/.gitignore b/testcases/kernel/syscalls/fchroot/.gitignore index 0697f10eb..12151270a 100644 --- a/testcases/kernel/syscalls/fchroot/.gitignore +++ b/testcases/kernel/syscalls/fchroot/.gitignore @@ -3,3 +3,4 @@ fchroot02 fchroot03 fchroot04 fchroot05 +fchroot06 diff --git a/testcases/kernel/syscalls/fchroot/fchroot06.c b/testcases/kernel/syscalls/fchroot/fchroot06.c new file mode 100644 index 000000000..a1293b932 --- /dev/null +++ b/testcases/kernel/syscalls/fchroot/fchroot06.c @@ -0,0 +1,90 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Copyright (C) 2026 SUSE LLC Andrea Cervesato + */ + +/*\ + * Test path walks under the failfs root. + * + * Once :manpage:`fchroot(2)` moved the process root into failfs, only + * lookups anchored at a file descriptor keep working: + * + * - lookups relative to the working directory, which stays in the real + * filesystem, keep working + * - lookups anchored at a pre-opened directory fd keep working, including + * resolution of relative symlinks + * - absolute symlinks restart the walk at the failfs root and fail with + * EOPNOTSUPP + * - ".." walks clamp at the top of the mount tree, not at the failfs + * root, so walking up from the working directory lands on the real + * root + * + * Root is required because entering failfs with the FD_FAILFS_ROOT + * sentinel requires CAP_SYS_CHROOT. + * + * 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/syscalls.h" +#include "tst_safe_file_at.h" + +#define UPWARDS "../../../../../../../../../.." + +static void run(void) +{ + if (!SAFE_FORK()) { + struct stat realroot, st; + int dfd, fd; + + SAFE_STAT("/", &realroot); + dfd = SAFE_OPEN(".", O_RDONLY | O_DIRECTORY); + + TST_EXP_PASS(tst_syscall(__NR_fchroot, FD_FAILFS_ROOT, 0), + "fchroot() with the FD_FAILFS_ROOT sentinel"); + + fd = SAFE_OPENAT(AT_FDCWD, ".", O_RDONLY | O_DIRECTORY); + SAFE_CLOSE(fd); + + fd = SAFE_OPENAT(dfd, "canary", O_WRONLY | O_CREAT, 0600); + SAFE_WRITE(SAFE_WRITE_ALL, fd, "x", 1); + SAFE_CLOSE(fd); + + fd = SAFE_OPENAT(dfd, "rel", O_RDONLY); + SAFE_CLOSE(fd); + + TST_EXP_FAIL2(openat(dfd, "abs", O_RDONLY), EOPNOTSUPP, + "resolution of an absolute symlink"); + + fd = SAFE_OPENAT(AT_FDCWD, UPWARDS, O_PATH); + SAFE_FSTAT(fd, &st); + TST_EXP_EXPR(st.st_dev == realroot.st_dev && + st.st_ino == realroot.st_ino, + "'..' walk clamps at the top of the mount tree"); + SAFE_CLOSE(fd); + + SAFE_CLOSE(dfd); + + exit(0); + } +} + +static void setup(void) +{ + SAFE_TOUCH("target", 0644, NULL); + SAFE_SYMLINK("target", "rel"); + SAFE_SYMLINK("/etc", "abs"); +} + +static struct tst_test test = { + .setup = setup, + .test_all = run, + .needs_root = 1, + .needs_tmpdir = 1, + .forks_child = 1, +}; -- 2.51.0 -- Mailing list info: https://lists.linux.it/listinfo/ltp