From 5d409034017e9f9f8c4392157d95511fc2e05d87 Mon Sep 17 00:00:00 2001 From: Martin Pitt Date: Wed, 27 May 2015 09:56:03 +0200 Subject: [PATCH] path-util: Fix path_is_mount_point for files MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Commits 27cc6f166 and f25afeb broke path_is_mount_point() for files (such as /etc/machine-id → /run/machine-id bind mounts) as with the factorization of fd_is_mount_point() we lost the parent directory. We cannot determine that from an fd only as openat(fd, "..") only works for directory fds. Change fd_is_mount_point() to behave like openat(): It now takes a file descriptor of the containing directory, a file name in it, and flags (which can be 0 or AT_SYMLINK_FOLLOW). Unlike name_to_handle_at() or openat(), fstatat() only accepts the inverse flag AT_SYMLINK_NOFOLLOW and complains with EINVAL about AT_SYMLINK_FOLLOW; so we need to transform the flags for that fallback. Adjust rm_rf_children() accordingly (only other caller of fd_is_mount_point() aside from path_is_mount_point()). Add test cases for files, links, and file bind mounts (the latter will only work when running as root). Split out a new test_path_is_mount_point() test case function as it got significantly larger now. --- src/shared/path-util.c | 31 +++++++++++----- src/shared/path-util.h | 2 +- src/shared/rm-rf.c | 2 +- src/test/test-path-util.c | 76 ++++++++++++++++++++++++++++++++------- 4 files changed, 87 insertions(+), 24 deletions(-) diff --git a/src/shared/path-util.c b/src/shared/path-util.c index 7090989fcb..8be479cd7f 100644 --- a/src/shared/path-util.c +++ b/src/shared/path-util.c @@ -509,7 +509,7 @@ static int fd_fdinfo_mnt_id(int fd, const char *filename, int flags, int *mnt_id return safe_atoi(p, mnt_id); } -int fd_is_mount_point(int fd) { +int fd_is_mount_point(int fd, const char *filename, int flags) { union file_handle_union h = FILE_HANDLE_INIT, h_parent = FILE_HANDLE_INIT; int mount_id = -1, mount_id_parent = -1; bool nosupp = false, check_st_dev = true; @@ -517,6 +517,7 @@ int fd_is_mount_point(int fd) { int r; assert(fd >= 0); + assert(filename); /* First we will try the name_to_handle_at() syscall, which * tells us the mount id and an opaque file "handle". It is @@ -541,7 +542,7 @@ int fd_is_mount_point(int fd) { * subvolumes have different st_dev, even though they aren't * real mounts of their own. */ - r = name_to_handle_at(fd, "", &h.handle, &mount_id, AT_EMPTY_PATH); + r = name_to_handle_at(fd, filename, &h.handle, &mount_id, flags); if (r < 0) { if (errno == ENOSYS) /* This kernel does not support name_to_handle_at() @@ -558,7 +559,7 @@ int fd_is_mount_point(int fd) { return -errno; } - r = name_to_handle_at(fd, "..", &h_parent.handle, &mount_id_parent, 0); + r = name_to_handle_at(fd, "", &h_parent.handle, &mount_id_parent, AT_EMPTY_PATH); if (r < 0) { if (errno == EOPNOTSUPP) { if (nosupp) @@ -593,13 +594,13 @@ int fd_is_mount_point(int fd) { return mount_id != mount_id_parent; fallback_fdinfo: - r = fd_fdinfo_mnt_id(fd, "", AT_EMPTY_PATH, &mount_id); + r = fd_fdinfo_mnt_id(fd, filename, flags, &mount_id); if (r == -EOPNOTSUPP) goto fallback_fstat; if (r < 0) return r; - r = fd_fdinfo_mnt_id(fd, "..", 0, &mount_id_parent); + r = fd_fdinfo_mnt_id(fd, "", AT_EMPTY_PATH, &mount_id_parent); if (r < 0) return r; @@ -615,10 +616,16 @@ fallback_fdinfo: check_st_dev = false; fallback_fstat: - if (fstatat(fd, "", &a, AT_EMPTY_PATH) < 0) + /* yay for fstatat() taking a different set of flags than the other + * _at() above */ + if (flags & AT_SYMLINK_FOLLOW) + flags &= ~AT_SYMLINK_FOLLOW; + else + flags |= AT_SYMLINK_NOFOLLOW; + if (fstatat(fd, filename, &a, flags) < 0) return -errno; - if (fstatat(fd, "..", &b, 0) < 0) + if (fstatat(fd, "", &b, AT_EMPTY_PATH) < 0) return -errno; /* A directory with same device and inode as its parent? Must @@ -632,17 +639,23 @@ fallback_fstat: int path_is_mount_point(const char *t, bool allow_symlink) { _cleanup_close_ int fd = -1; + _cleanup_free_ char *parent = NULL; + int r; assert(t); if (path_equal(t, "/")) return 1; - fd = openat(AT_FDCWD, t, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|(allow_symlink ? 0 : O_PATH)); + r = path_get_parent(t, &parent); + if (r < 0) + return r; + + fd = openat(AT_FDCWD, parent, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_PATH); if (fd < 0) return -errno; - return fd_is_mount_point(fd); + return fd_is_mount_point(fd, basename(t), (allow_symlink ? AT_SYMLINK_FOLLOW : 0)); } int path_is_read_only_fs(const char *path) { diff --git a/src/shared/path-util.h b/src/shared/path-util.h index 4f45cfd2b7..38ad799ba0 100644 --- a/src/shared/path-util.h +++ b/src/shared/path-util.h @@ -53,7 +53,7 @@ char** path_strv_make_absolute_cwd(char **l); char** path_strv_resolve(char **l, const char *prefix); char** path_strv_resolve_uniq(char **l, const char *prefix); -int fd_is_mount_point(int fd); +int fd_is_mount_point(int fd, const char *filename, int flags); int path_is_mount_point(const char *path, bool allow_symlink); int path_is_read_only_fs(const char *path); int path_is_os_tree(const char *path); diff --git a/src/shared/rm-rf.c b/src/shared/rm-rf.c index a89e8afc2a..bafd483be2 100644 --- a/src/shared/rm-rf.c +++ b/src/shared/rm-rf.c @@ -103,7 +103,7 @@ int rm_rf_children(int fd, RemoveFlags flags, struct stat *root_dev) { } /* Stop at mount points */ - r = fd_is_mount_point(subdir_fd); + r = fd_is_mount_point(fd, de->d_name, 0); if (r < 0) { if (ret == 0 && r != -ENOENT) ret = r; diff --git a/src/test/test-path-util.c b/src/test/test-path-util.c index 09f0f2f89e..80782ff902 100644 --- a/src/test/test-path-util.c +++ b/src/test/test-path-util.c @@ -21,6 +21,7 @@ #include #include +#include #include "path-util.h" #include "util.h" @@ -88,21 +89,9 @@ static void test_path(void) { test_parent("/aa///file...", "/aa///"); test_parent("file.../", NULL); - assert_se(path_is_mount_point("/", true) > 0); - assert_se(path_is_mount_point("/", false) > 0); - fd = open("/", O_RDONLY|O_CLOEXEC|O_DIRECTORY|O_NOCTTY); assert_se(fd >= 0); - assert_se(fd_is_mount_point(fd) > 0); - - assert_se(path_is_mount_point("/proc", true) > 0); - assert_se(path_is_mount_point("/proc", false) > 0); - - assert_se(path_is_mount_point("/proc/1", true) == 0); - assert_se(path_is_mount_point("/proc/1", false) == 0); - - assert_se(path_is_mount_point("/sys", true) > 0); - assert_se(path_is_mount_point("/sys", false) > 0); + assert_se(fd_is_mount_point(fd, "/", 0) > 0); { char p1[] = "aaa/bbb////ccc"; @@ -322,6 +311,66 @@ static void test_prefix_root(void) { test_prefix_root_one("/foo///", "//bar", "/foo/bar"); } +static void test_path_is_mount_point(void) { + int fd, rt, rf, rlt, rlf; + char tmp_dir[] = "/tmp/test-path-is-mount-point-XXXXXX"; + _cleanup_free_ char *file1 = NULL, *file2 = NULL, *link1 = NULL, *link2 = NULL; + + assert_se(path_is_mount_point("/", true) > 0); + assert_se(path_is_mount_point("/", false) > 0); + + assert_se(path_is_mount_point("/proc", true) > 0); + assert_se(path_is_mount_point("/proc", false) > 0); + + assert_se(path_is_mount_point("/proc/1", true) == 0); + assert_se(path_is_mount_point("/proc/1", false) == 0); + + assert_se(path_is_mount_point("/sys", true) > 0); + assert_se(path_is_mount_point("/sys", false) > 0); + + /* file mountpoints */ + assert_se(mkdtemp(tmp_dir) != NULL); + file1 = path_join(NULL, tmp_dir, "file1"); + assert_se(file1); + file2 = path_join(NULL, tmp_dir, "file2"); + assert_se(file2); + fd = open(file1, O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, 0664); + assert_se(fd > 0); + close(fd); + fd = open(file2, O_WRONLY|O_CREAT|O_EXCL|O_CLOEXEC, 0664); + assert_se(fd > 0); + close(fd); + link1 = path_join(NULL, tmp_dir, "link1"); + assert_se(link1); + assert_se(symlink("file1", link1) == 0); + link2 = path_join(NULL, tmp_dir, "link2"); + assert_se(link1); + assert_se(symlink("file2", link2) == 0); + + assert_se(path_is_mount_point(file1, true) == 0); + assert_se(path_is_mount_point(file1, false) == 0); + assert_se(path_is_mount_point(link1, true) == 0); + assert_se(path_is_mount_point(link1, false) == 0); + + /* this test will only work as root */ + if (mount(file1, file2, NULL, MS_BIND, NULL) >= 0) { + rf = path_is_mount_point(file2, false); + rt = path_is_mount_point(file2, true); + rlf = path_is_mount_point(link2, false); + rlt = path_is_mount_point(link2, true); + + assert_se(umount(file2) == 0); + + assert_se(rf == 1); + assert_se(rt == 1); + assert_se(rlf == 0); + assert_se(rlt == 1); + } else + printf("Skipping bind mount file test: %m\n"); + + assert_se(rm_rf(tmp_dir, REMOVE_ROOT|REMOVE_PHYSICAL) == 0); +} + int main(int argc, char **argv) { test_path(); test_find_binary(argv[0], true); @@ -333,6 +382,7 @@ int main(int argc, char **argv) { test_strv_resolve(); test_path_startswith(); test_prefix_root(); + test_path_is_mount_point(); return 0; }