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v261
src/shared/rm-rf.c
555 строк
19 KB
Lennart Poettering
tree-wide: use stat_verify_directory() more
13 апр 2026, 14:20
13 апр 2026, 14:20
4031a73
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/* SPDX-License-Identifier: LGPL-2.1-or-later */ #include <fcntl.h> #include <linux/magic.h> #include <unistd.h> #include "alloc-util.h" #include "btrfs-util.h" #include "dirent-util.h" #include "errno-util.h" #include "fd-util.h" #include "fs-util.h" #include "log.h" #include "mountpoint-util.h" #include "path-util.h" #include "rm-rf.h" #include "stat-util.h" #include "string-util.h" /* We treat tmpfs/ramfs + cgroupfs as non-physical file systems. cgroupfs is similar to tmpfs in a way * after all: we can create arbitrary directory hierarchies in it, and hence can also use rm_rf() on it * to remove those again. */ static bool is_physical_fs(const struct statfs *sfs) { return !is_temporary_fs(sfs) && !is_fs_type(sfs, CGROUP2_SUPER_MAGIC); } static int patch_dirfd_mode( int dfd, bool refuse_already_set, mode_t *ret_old_mode) { struct stat st; int r; assert(dfd >= 0); assert(ret_old_mode); if (fstat(dfd, &st) < 0) return -errno; r = stat_verify_directory(&st); if (r < 0) return r; if (FLAGS_SET(st.st_mode, 0700)) { /* Already set? */ if (refuse_already_set) return -EACCES; /* original error */ *ret_old_mode = st.st_mode; return 0; } if (st.st_uid != geteuid()) /* this only works if the UID matches ours */ return -EACCES; r = fchmod_opath(dfd, (st.st_mode | 0700) & 07777); if (r < 0) return r; *ret_old_mode = st.st_mode; return 1; } int unlinkat_harder(int dfd, const char *filename, int unlink_flags, RemoveFlags remove_flags) { mode_t old_mode; int r; /* Like unlinkat(), but tries harder: if we get EACCESS we'll try to set the r/w/x bits on the * directory. This is useful if we run unprivileged and have some files where the w bit is * missing. */ if (unlinkat(dfd, filename, unlink_flags) >= 0) return 0; if (errno != EACCES || !FLAGS_SET(remove_flags, REMOVE_CHMOD)) return -errno; r = patch_dirfd_mode(dfd, /* refuse_already_set= */ true, &old_mode); if (r < 0) return r; if (unlinkat(dfd, filename, unlink_flags) < 0) { r = -errno; /* Try to restore the original access mode if this didn't work */ (void) fchmod(dfd, old_mode & 07777); return r; } if (FLAGS_SET(remove_flags, REMOVE_CHMOD_RESTORE) && fchmod(dfd, old_mode & 07777) < 0) return -errno; /* If this worked, we won't reset the old mode by default, since we'll need it for other entries too, * and we should destroy the whole thing */ return 0; } int fstatat_harder(int dfd, const char *filename, struct stat *ret, int fstatat_flags, RemoveFlags remove_flags) { mode_t old_mode; int r; /* Like unlink_harder() but does the same for fstatat() */ if (fstatat(dfd, filename, ret, fstatat_flags) >= 0) return 0; if (errno != EACCES || !FLAGS_SET(remove_flags, REMOVE_CHMOD)) return -errno; r = patch_dirfd_mode(dfd, /* refuse_already_set= */ true, &old_mode); if (r < 0) return r; if (fstatat(dfd, filename, ret, fstatat_flags) < 0) { r = -errno; (void) fchmod(dfd, old_mode & 07777); return r; } if (FLAGS_SET(remove_flags, REMOVE_CHMOD_RESTORE) && fchmod(dfd, old_mode & 07777) < 0) return -errno; return 0; } static int openat_harder(int dfd, const char *path, int open_flags, RemoveFlags remove_flags, mode_t *ret_old_mode) { _cleanup_close_ int pfd = -EBADF, fd = -EBADF; bool chmod_done = false; mode_t old_mode; int r; assert(dfd >= 0 || dfd == AT_FDCWD); assert(path); /* Unlike unlink_harder() and fstatat_harder(), this chmod the specified path. */ if (FLAGS_SET(open_flags, O_PATH) || !FLAGS_SET(open_flags, O_DIRECTORY) || !FLAGS_SET(remove_flags, REMOVE_CHMOD)) { fd = RET_NERRNO(openat(dfd, path, open_flags)); if (fd < 0) return fd; if (ret_old_mode) { struct stat st; if (fstat(fd, &st) < 0) return -errno; *ret_old_mode = st.st_mode; } return TAKE_FD(fd); } pfd = RET_NERRNO(openat(dfd, path, (open_flags & (O_CLOEXEC|O_DIRECTORY|O_NOFOLLOW)) | O_PATH)); if (pfd < 0) return pfd; if (FLAGS_SET(remove_flags, REMOVE_CHMOD)) { r = patch_dirfd_mode(pfd, /* refuse_already_set= */ false, &old_mode); if (r < 0) return r; chmod_done = r; } fd = fd_reopen(pfd, open_flags & ~O_NOFOLLOW); if (fd < 0) { if (chmod_done) (void) fchmod_opath(pfd, old_mode & 07777); return fd; } if (ret_old_mode) *ret_old_mode = old_mode; return TAKE_FD(fd); } static int rm_rf_children_impl( int fd, RemoveFlags flags, const struct stat *root_dev, mode_t old_mode); static int rm_rf_inner_child( int fd, const char *fname, int is_dir, RemoveFlags flags, const struct stat *root_dev, bool allow_recursion) { struct stat st; int r, q = 0; assert(fd >= 0); assert(fname); if (is_dir < 0 || root_dev || (is_dir > 0 && (root_dev || (flags & REMOVE_SUBVOLUME)))) { r = fstatat_harder(fd, fname, &st, AT_SYMLINK_NOFOLLOW, flags); if (r < 0) return r; is_dir = S_ISDIR(st.st_mode); } if (is_dir) { /* If root_dev is set, remove subdirectories only if device is same */ if (root_dev && st.st_dev != root_dev->st_dev) return 0; /* Stop at mount points */ r = is_mount_point_at(fd, fname, 0); if (r < 0) return r; if (r > 0) return 0; if ((flags & REMOVE_SUBVOLUME) && btrfs_might_be_subvol(&st)) { /* This could be a subvolume, try to remove it */ r = btrfs_subvol_remove_at(fd, fname, BTRFS_REMOVE_RECURSIVE|BTRFS_REMOVE_QUOTA); if (r < 0) { if (!IN_SET(r, -ENOTTY, -EINVAL)) return r; /* ENOTTY, then it wasn't a btrfs subvolume, continue below. */ } else /* It was a subvolume, done. */ return 1; } if (!allow_recursion) return -EISDIR; mode_t old_mode; int subdir_fd = openat_harder(fd, fname, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME, flags, &old_mode); if (subdir_fd < 0) return subdir_fd; /* We pass REMOVE_PHYSICAL here, to avoid doing the fstatfs() to check the file system type * again for each directory */ q = rm_rf_children_impl(subdir_fd, flags | REMOVE_PHYSICAL, root_dev, old_mode); } else if (flags & REMOVE_ONLY_DIRECTORIES) return 0; r = unlinkat_harder(fd, fname, is_dir ? AT_REMOVEDIR : 0, flags); if (r < 0) return r; if (q < 0) return q; return 1; } typedef struct TodoEntry { DIR *dir; /* A directory that we were operating on. */ char *dirname; /* The filename of that directory itself. */ mode_t old_mode; /* The original file mode. */ } TodoEntry; static void free_todo_entries(TodoEntry **todos) { assert(todos); for (TodoEntry *x = *todos; x && x->dir; x++) { closedir(x->dir); free(x->dirname); } freep(todos); } int rm_rf_children( int fd, RemoveFlags flags, const struct stat *root_dev) { struct stat st; assert(fd >= 0); if (fstat(fd, &st) < 0) return -errno; return rm_rf_children_impl(fd, flags, root_dev, st.st_mode); } static int rm_rf_children_impl( int fd, RemoveFlags flags, const struct stat *root_dev, mode_t old_mode) { _cleanup_(free_todo_entries) TodoEntry *todos = NULL; size_t n_todo = 0; _cleanup_free_ char *dirname = NULL; /* Set when we are recursing and want to delete ourselves */ int ret = 0, r; /* Return the first error we run into, but nevertheless try to go on. * The passed fd is closed in all cases, including on failure. */ for (;;) { /* This loop corresponds to the directory nesting level. */ _cleanup_closedir_ DIR *d = NULL; if (n_todo > 0) { /* We know that we are in recursion here, because n_todo is set. * We need to remove the inner directory we were operating on. */ assert(dirname); r = unlinkat_harder(dirfd(todos[n_todo-1].dir), dirname, AT_REMOVEDIR, flags); if (r < 0 && r != -ENOENT) { if (ret == 0) ret = r; if (FLAGS_SET(flags, REMOVE_CHMOD_RESTORE)) (void) fchmodat(dirfd(todos[n_todo-1].dir), dirname, old_mode & 07777, 0); } dirname = mfree(dirname); /* And now let's back out one level up */ n_todo--; d = TAKE_PTR(todos[n_todo].dir); dirname = TAKE_PTR(todos[n_todo].dirname); old_mode = todos[n_todo].old_mode; assert(d); fd = dirfd(d); /* Retrieve the file descriptor from the DIR object */ assert(fd >= 0); } else { next_fd: assert(fd >= 0); d = fdopendir(fd); if (!d) { safe_close(fd); return -errno; } fd = dirfd(d); /* We donated the fd to fdopendir(). Let's make sure we sure we have * the right descriptor even if it were to internally invalidate the * one we passed. */ if (!(flags & REMOVE_PHYSICAL)) { struct statfs sfs; if (fstatfs(fd, &sfs) < 0) return -errno; if (is_physical_fs(&sfs)) { /* We refuse to clean physical file systems with this call, unless * explicitly requested. This is extra paranoia just to be sure we * never ever remove non-state data. */ _cleanup_free_ char *path = NULL; (void) fd_get_path(fd, &path); return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Attempted to remove disk file system under \"%s\", and we can't allow that.", strna(path)); } } } FOREACH_DIRENT_ALL(de, d, return -errno) { int is_dir; if (dot_or_dot_dot(de->d_name)) continue; is_dir = de->d_type == DT_UNKNOWN ? -1 : de->d_type == DT_DIR; r = rm_rf_inner_child(fd, de->d_name, is_dir, flags, root_dev, false); if (r == -EISDIR) { /* Push the current working state onto the todo list */ if (!GREEDY_REALLOC0(todos, n_todo + 2)) return log_oom(); _cleanup_free_ char *newdirname = strdup(de->d_name); if (!newdirname) return log_oom(); mode_t mode; int newfd = openat_harder(fd, de->d_name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME, flags, &mode); if (newfd >= 0) { todos[n_todo++] = (TodoEntry) { .dir = TAKE_PTR(d), .dirname = TAKE_PTR(dirname), .old_mode = old_mode }; fd = newfd; dirname = TAKE_PTR(newdirname); old_mode = mode; goto next_fd; } else if (newfd != -ENOENT && ret == 0) ret = newfd; } else if (r < 0 && r != -ENOENT && ret == 0) ret = r; } if (FLAGS_SET(flags, REMOVE_SYNCFS) && syncfs(fd) < 0 && ret >= 0) ret = -errno; if (n_todo == 0) { if (FLAGS_SET(flags, REMOVE_CHMOD_RESTORE) && fchmod(fd, old_mode & 07777) < 0 && ret >= 0) ret = -errno; break; } } return ret; } int rm_rf_at(int dir_fd, const char *path, RemoveFlags flags) { mode_t old_mode; int fd, r, q = 0; assert(dir_fd >= 0 || dir_fd == AT_FDCWD); assert(path); /* For now, don't support dropping subvols when also only dropping directories, since we can't do * this race-freely. */ if (FLAGS_SET(flags, REMOVE_ONLY_DIRECTORIES|REMOVE_SUBVOLUME)) return -EINVAL; /* We refuse to clean the root file system with this call. This is extra paranoia to never cause a * really seriously broken system. */ if (path_is_root_at(dir_fd, path) > 0) return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Attempted to remove entire root file system, and we can't allow that."); if (FLAGS_SET(flags, REMOVE_SUBVOLUME | REMOVE_ROOT | REMOVE_PHYSICAL)) { /* Try to remove as subvolume first */ r = btrfs_subvol_remove_at(dir_fd, path, BTRFS_REMOVE_RECURSIVE|BTRFS_REMOVE_QUOTA); if (r >= 0) return r; if (FLAGS_SET(flags, REMOVE_MISSING_OK) && r == -ENOENT) return 0; if (!IN_SET(r, -ENOTTY, -EINVAL, -ENOTDIR, -EPERM, -EACCES)) return r; /* Not btrfs or not a subvolume, or permissions are not available (but might if we go via unlinkat()) */ } /* In the next step we'll try to open the directory in order to enumerate its contents. This might * not work due to perms, but we might still be able to delete it, hence let's try that first. */ if (FLAGS_SET(flags, REMOVE_ROOT | REMOVE_PHYSICAL)) if (unlinkat(dir_fd, path, AT_REMOVEDIR) >= 0) return 0; fd = openat_harder(dir_fd, path, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME, flags, &old_mode); if (fd >= 0) { /* We have a dir */ r = rm_rf_children_impl(fd, flags, NULL, old_mode); if (FLAGS_SET(flags, REMOVE_ROOT)) q = RET_NERRNO(unlinkat(dir_fd, path, AT_REMOVEDIR)); } else { r = fd; if (FLAGS_SET(flags, REMOVE_MISSING_OK) && r == -ENOENT) return 0; if (!IN_SET(r, -ENOTDIR, -ELOOP)) return r; if (FLAGS_SET(flags, REMOVE_ONLY_DIRECTORIES) || !FLAGS_SET(flags, REMOVE_ROOT)) return 0; if (!FLAGS_SET(flags, REMOVE_PHYSICAL)) { struct statfs s; r = xstatfsat(dir_fd, path, &s); if (r < 0) return r; if (is_physical_fs(&s)) return log_error_errno(SYNTHETIC_ERRNO(EPERM), "Attempted to remove files from a disk file system under \"%s\", refusing.", path); } r = 0; q = RET_NERRNO(unlinkat(dir_fd, path, 0)); } if (r < 0) return r; if (q < 0 && (q != -ENOENT || !FLAGS_SET(flags, REMOVE_MISSING_OK))) return q; return 0; } int rm_rf_child(int fd, const char *name, RemoveFlags flags) { /* Removes one specific child of the specified directory */ if (fd < 0) return -EBADF; if (!filename_is_valid(name)) return -EINVAL; if ((flags & (REMOVE_ROOT|REMOVE_MISSING_OK)) != 0) /* Doesn't really make sense here, we are not supposed to remove 'fd' anyway */ return -EINVAL; if (FLAGS_SET(flags, REMOVE_ONLY_DIRECTORIES|REMOVE_SUBVOLUME)) return -EINVAL; return rm_rf_inner_child(fd, name, -1, flags, NULL, true); } const char* rm_rf_safe(const char *p) { PROTECT_ERRNO; if (!p) return NULL; (void) rm_rf(p, REMOVE_ROOT|REMOVE_MISSING_OK|REMOVE_CHMOD); return NULL; } char* rm_rf_physical_and_free(char *p) { PROTECT_ERRNO; if (!p) return NULL; (void) rm_rf(p, REMOVE_ROOT|REMOVE_PHYSICAL|REMOVE_MISSING_OK|REMOVE_CHMOD); return mfree(p); } char* rm_rf_subvolume_and_free(char *p) { PROTECT_ERRNO; if (!p) return NULL; (void) rm_rf(p, REMOVE_ROOT|REMOVE_PHYSICAL|REMOVE_SUBVOLUME|REMOVE_MISSING_OK|REMOVE_CHMOD); return mfree(p); }