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Diffstat (limited to '')
| -rw-r--r-- | src/remove.c | 621 |
1 files changed, 621 insertions, 0 deletions
diff --git a/src/remove.c b/src/remove.c new file mode 100644 index 0000000..2d40c55 --- /dev/null +++ b/src/remove.c @@ -0,0 +1,621 @@ +/* remove.c -- core functions for removing files and directories + Copyright (C) 1988-2020 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +/* Extracted from rm.c, librarified, then rewritten twice by Jim Meyering. */ + +#include <config.h> +#include <stdio.h> +#include <sys/types.h> +#include <assert.h> + +#include "system.h" +#include "error.h" +#include "file-type.h" +#include "filenamecat.h" +#include "ignore-value.h" +#include "remove.h" +#include "root-dev-ino.h" +#include "write-any-file.h" +#include "xfts.h" +#include "yesno.h" + +enum Ternary + { + T_UNKNOWN = 2, + T_NO, + T_YES + }; +typedef enum Ternary Ternary; + +/* The prompt function may be called twice for a given directory. + The first time, we ask whether to descend into it, and the + second time, we ask whether to remove it. */ +enum Prompt_action + { + PA_DESCEND_INTO_DIR = 2, + PA_REMOVE_DIR + }; + +/* D_TYPE(D) is the type of directory entry D if known, DT_UNKNOWN + otherwise. */ +#if ! HAVE_STRUCT_DIRENT_D_TYPE +/* Any int values will do here, so long as they're distinct. + Undef any existing macros out of the way. */ +# undef DT_UNKNOWN +# undef DT_DIR +# undef DT_LNK +# define DT_UNKNOWN 0 +# define DT_DIR 1 +# define DT_LNK 2 +#endif + +/* Like fstatat, but cache the result. If ST->st_size is -1, the + status has not been gotten yet. If less than -1, fstatat failed + with errno == ST->st_ino. Otherwise, the status has already + been gotten, so return 0. */ +static int +cache_fstatat (int fd, char const *file, struct stat *st, int flag) +{ + if (st->st_size == -1 && fstatat (fd, file, st, flag) != 0) + { + st->st_size = -2; + st->st_ino = errno; + } + if (0 <= st->st_size) + return 0; + errno = (int) st->st_ino; + return -1; +} + +/* Initialize a fstatat cache *ST. Return ST for convenience. */ +static inline struct stat * +cache_stat_init (struct stat *st) +{ + st->st_size = -1; + return st; +} + +/* Return 1 if FILE is an unwritable non-symlink, + 0 if it is writable or some other type of file, + -1 and set errno if there is some problem in determining the answer. + Set *BUF to the file status. */ +static int +write_protected_non_symlink (int fd_cwd, + char const *file, + struct stat *buf) +{ + if (can_write_any_file ()) + return 0; + if (cache_fstatat (fd_cwd, file, buf, AT_SYMLINK_NOFOLLOW) != 0) + return -1; + if (S_ISLNK (buf->st_mode)) + return 0; + /* Here, we know FILE is not a symbolic link. */ + + /* In order to be reentrant -- i.e., to avoid changing the working + directory, and at the same time to be able to deal with alternate + access control mechanisms (ACLs, xattr-style attributes) and + arbitrarily deep trees -- we need a function like eaccessat, i.e., + like Solaris' eaccess, but fd-relative, in the spirit of openat. */ + + /* In the absence of a native eaccessat function, here are some of + the implementation choices [#4 and #5 were suggested by Paul Eggert]: + 1) call openat with O_WRONLY|O_NOCTTY + Disadvantage: may create the file and doesn't work for directory, + may mistakenly report 'unwritable' for EROFS or ACLs even though + perm bits say the file is writable. + + 2) fake eaccessat (save_cwd, fchdir, call euidaccess, restore_cwd) + Disadvantage: changes working directory (not reentrant) and can't + work if save_cwd fails. + + 3) if (euidaccess (full_name, W_OK) == 0) + Disadvantage: doesn't work if full_name is too long. + Inefficient for very deep trees (O(Depth^2)). + + 4) If the full pathname is sufficiently short (say, less than + PATH_MAX or 8192 bytes, whichever is shorter): + use method (3) (i.e., euidaccess (full_name, W_OK)); + Otherwise: vfork, fchdir in the child, run euidaccess in the + child, then the child exits with a status that tells the parent + whether euidaccess succeeded. + + This avoids the O(N**2) algorithm of method (3), and it also avoids + the failure-due-to-too-long-file-names of method (3), but it's fast + in the normal shallow case. It also avoids the lack-of-reentrancy + and the save_cwd problems. + Disadvantage; it uses a process slot for very-long file names, + and would be very slow for hierarchies with many such files. + + 5) If the full file name is sufficiently short (say, less than + PATH_MAX or 8192 bytes, whichever is shorter): + use method (3) (i.e., euidaccess (full_name, W_OK)); + Otherwise: look just at the file bits. Perhaps issue a warning + the first time this occurs. + + This is like (4), except for the "Otherwise" case where it isn't as + "perfect" as (4) but is considerably faster. It conforms to current + POSIX, and is uniformly better than what Solaris and FreeBSD do (they + mess up with long file names). */ + + { + if (faccessat (fd_cwd, file, W_OK, AT_EACCESS) == 0) + return 0; + + return errno == EACCES ? 1 : -1; + } +} + +/* Prompt whether to remove FILENAME (ent->, if required via a combination of + the options specified by X and/or file attributes. If the file may + be removed, return RM_OK. If the user declines to remove the file, + return RM_USER_DECLINED. If not ignoring missing files and we + cannot lstat FILENAME, then return RM_ERROR. + + IS_DIR is true if ENT designates a directory, false otherwise. + + Depending on MODE, ask whether to 'descend into' or to 'remove' the + directory FILENAME. MODE is ignored when FILENAME is not a directory. + Set *IS_EMPTY_P to T_YES if FILENAME is an empty directory, and it is + appropriate to try to remove it with rmdir (e.g. recursive mode). + Don't even try to set *IS_EMPTY_P when MODE == PA_REMOVE_DIR. */ +static enum RM_status +prompt (FTS const *fts, FTSENT const *ent, bool is_dir, + struct rm_options const *x, enum Prompt_action mode, + Ternary *is_empty_p) +{ + int fd_cwd = fts->fts_cwd_fd; + char const *full_name = ent->fts_path; + char const *filename = ent->fts_accpath; + if (is_empty_p) + *is_empty_p = T_UNKNOWN; + + struct stat st; + struct stat *sbuf = &st; + cache_stat_init (sbuf); + + int dirent_type = is_dir ? DT_DIR : DT_UNKNOWN; + int write_protected = 0; + + bool is_empty = false; + if (is_empty_p) + { + is_empty = is_empty_dir (fd_cwd, filename); + *is_empty_p = is_empty ? T_YES : T_NO; + } + + /* When nonzero, this indicates that we failed to remove a child entry, + either because the user declined an interactive prompt, or due to + some other failure, like permissions. */ + if (ent->fts_number) + return RM_USER_DECLINED; + + if (x->interactive == RMI_NEVER) + return RM_OK; + + int wp_errno = 0; + if (!x->ignore_missing_files + && ((x->interactive == RMI_ALWAYS) || x->stdin_tty) + && dirent_type != DT_LNK) + { + write_protected = write_protected_non_symlink (fd_cwd, filename, sbuf); + wp_errno = errno; + } + + if (write_protected || x->interactive == RMI_ALWAYS) + { + if (0 <= write_protected && dirent_type == DT_UNKNOWN) + { + if (cache_fstatat (fd_cwd, filename, sbuf, AT_SYMLINK_NOFOLLOW) == 0) + { + if (S_ISLNK (sbuf->st_mode)) + dirent_type = DT_LNK; + else if (S_ISDIR (sbuf->st_mode)) + dirent_type = DT_DIR; + /* Otherwise it doesn't matter, so leave it DT_UNKNOWN. */ + } + else + { + /* This happens, e.g., with 'rm '''. */ + write_protected = -1; + wp_errno = errno; + } + } + + if (0 <= write_protected) + switch (dirent_type) + { + case DT_LNK: + /* Using permissions doesn't make sense for symlinks. */ + if (x->interactive != RMI_ALWAYS) + return RM_OK; + break; + + case DT_DIR: + /* Unless we're either deleting directories or deleting + recursively, we want to raise an EISDIR error rather than + prompting the user */ + if ( ! (x->recursive || (x->remove_empty_directories && is_empty))) + { + write_protected = -1; + wp_errno = EISDIR; + } + break; + } + + char const *quoted_name = quoteaf (full_name); + + if (write_protected < 0) + { + error (0, wp_errno, _("cannot remove %s"), quoted_name); + return RM_ERROR; + } + + /* Issue the prompt. */ + if (dirent_type == DT_DIR + && mode == PA_DESCEND_INTO_DIR + && !is_empty) + fprintf (stderr, + (write_protected + ? _("%s: descend into write-protected directory %s? ") + : _("%s: descend into directory %s? ")), + program_name, quoted_name); + else + { + if (cache_fstatat (fd_cwd, filename, sbuf, AT_SYMLINK_NOFOLLOW) != 0) + { + error (0, errno, _("cannot remove %s"), quoted_name); + return RM_ERROR; + } + + fprintf (stderr, + (write_protected + /* TRANSLATORS: In the next two strings the second %s is + replaced by the type of the file. To avoid grammatical + problems, it may be more convenient to translate these + strings instead as: "%1$s: %3$s is write-protected and + is of type '%2$s' -- remove it? ". */ + ? _("%s: remove write-protected %s %s? ") + : _("%s: remove %s %s? ")), + program_name, file_type (sbuf), quoted_name); + } + + if (!yesno ()) + return RM_USER_DECLINED; + } + return RM_OK; +} + +/* When a function like unlink, rmdir, or fstatat fails with an errno + value of ERRNUM, return true if the specified file system object + is guaranteed not to exist; otherwise, return false. */ +static inline bool +nonexistent_file_errno (int errnum) +{ + /* Do not include ELOOP here, since the specified file may indeed + exist, but be (in)accessible only via too long a symlink chain. + Likewise for ENAMETOOLONG, since rm -f ./././.../foo may fail + if the "..." part expands to a long enough sequence of "./"s, + even though ./foo does indeed exist. + + Another case to consider is when a particular name is invalid for + a given file system. In 2011, smbfs returns EINVAL, but the next + revision of POSIX will require EILSEQ for that situation: + http://austingroupbugs.net/view.php?id=293 + */ + + switch (errnum) + { + case EILSEQ: + case EINVAL: + case ENOENT: + case ENOTDIR: + return true; + default: + return false; + } +} + +/* Encapsulate the test for whether the errno value, ERRNUM, is ignorable. */ +static inline bool +ignorable_missing (struct rm_options const *x, int errnum) +{ + return x->ignore_missing_files && nonexistent_file_errno (errnum); +} + +/* Tell fts not to traverse into the hierarchy at ENT. */ +static void +fts_skip_tree (FTS *fts, FTSENT *ent) +{ + fts_set (fts, ent, FTS_SKIP); + /* Ensure that we do not process ENT a second time. */ + ignore_value (fts_read (fts)); +} + +/* Upon unlink failure, or when the user declines to remove ENT, mark + each of its ancestor directories, so that we know not to prompt for + its removal. */ +static void +mark_ancestor_dirs (FTSENT *ent) +{ + FTSENT *p; + for (p = ent->fts_parent; FTS_ROOTLEVEL <= p->fts_level; p = p->fts_parent) + { + if (p->fts_number) + break; + p->fts_number = 1; + } +} + +/* Remove the file system object specified by ENT. IS_DIR specifies + whether it is expected to be a directory or non-directory. + Return RM_OK upon success, else RM_ERROR. */ +static enum RM_status +excise (FTS *fts, FTSENT *ent, struct rm_options const *x, bool is_dir) +{ + int flag = is_dir ? AT_REMOVEDIR : 0; + if (unlinkat (fts->fts_cwd_fd, ent->fts_accpath, flag) == 0) + { + if (x->verbose) + { + printf ((is_dir + ? _("removed directory %s\n") + : _("removed %s\n")), quoteaf (ent->fts_path)); + } + return RM_OK; + } + + /* The unlinkat from kernels like linux-2.6.32 reports EROFS even for + nonexistent files. When the file is indeed missing, map that to ENOENT, + so that rm -f ignores it, as required. Even without -f, this is useful + because it makes rm print the more precise diagnostic. */ + if (errno == EROFS) + { + struct stat st; + if ( ! (lstatat (fts->fts_cwd_fd, ent->fts_accpath, &st) + && errno == ENOENT)) + errno = EROFS; + } + + if (ignorable_missing (x, errno)) + return RM_OK; + + /* When failing to rmdir an unreadable directory, we see errno values + like EISDIR or ENOTDIR (or, on Solaris 10, EEXIST), but they would be + meaningless in a diagnostic. When that happens and the errno value + from the failed open is EPERM or EACCES, use the earlier, more + descriptive errno value. */ + if (ent->fts_info == FTS_DNR + && (errno == ENOTEMPTY || errno == EISDIR || errno == ENOTDIR + || errno == EEXIST) + && (ent->fts_errno == EPERM || ent->fts_errno == EACCES)) + errno = ent->fts_errno; + error (0, errno, _("cannot remove %s"), quoteaf (ent->fts_path)); + mark_ancestor_dirs (ent); + return RM_ERROR; +} + +/* This function is called once for every file system object that fts + encounters. fts performs a depth-first traversal. + A directory is usually processed twice, first with fts_info == FTS_D, + and later, after all of its entries have been processed, with FTS_DP. + Return RM_ERROR upon error, RM_USER_DECLINED for a negative response + to an interactive prompt, and otherwise, RM_OK. */ +static enum RM_status +rm_fts (FTS *fts, FTSENT *ent, struct rm_options const *x) +{ + switch (ent->fts_info) + { + case FTS_D: /* preorder directory */ + if (! x->recursive + && !(x->remove_empty_directories + && is_empty_dir (fts->fts_cwd_fd, ent->fts_accpath))) + { + /* This is the first (pre-order) encounter with a directory + that we cannot delete. + Not recursive, and it's not an empty directory (if we're removing + them) so arrange to skip contents. */ + int err = x->remove_empty_directories ? ENOTEMPTY : EISDIR; + error (0, err, _("cannot remove %s"), quoteaf (ent->fts_path)); + mark_ancestor_dirs (ent); + fts_skip_tree (fts, ent); + return RM_ERROR; + } + + /* Perform checks that can apply only for command-line arguments. */ + if (ent->fts_level == FTS_ROOTLEVEL) + { + /* POSIX says: + If the basename of a command line argument is "." or "..", + diagnose it and do nothing more with that argument. */ + if (dot_or_dotdot (last_component (ent->fts_accpath))) + { + error (0, 0, + _("refusing to remove %s or %s directory: skipping %s"), + quoteaf_n (0, "."), quoteaf_n (1, ".."), + quoteaf_n (2, ent->fts_path)); + fts_skip_tree (fts, ent); + return RM_ERROR; + } + + /* POSIX also says: + If a command line argument resolves to "/" (and --preserve-root + is in effect -- default) diagnose and skip it. */ + if (ROOT_DEV_INO_CHECK (x->root_dev_ino, ent->fts_statp)) + { + ROOT_DEV_INO_WARN (ent->fts_path); + fts_skip_tree (fts, ent); + return RM_ERROR; + } + + /* If a command line argument is a mount point and + --preserve-root=all is in effect, diagnose and skip it. + This doesn't handle "/", but that's handled above. */ + if (x->preserve_all_root) + { + bool failed = false; + char *parent = file_name_concat (ent->fts_accpath, "..", NULL); + struct stat statbuf; + + if (!parent || lstat (parent, &statbuf)) + { + error (0, 0, + _("failed to stat %s: skipping %s"), + quoteaf_n (0, parent), + quoteaf_n (1, ent->fts_accpath)); + failed = true; + } + + free (parent); + + if (failed || fts->fts_dev != statbuf.st_dev) + { + if (! failed) + { + error (0, 0, + _("skipping %s, since it's on a different device"), + quoteaf (ent->fts_path)); + error (0, 0, _("and --preserve-root=all is in effect")); + } + fts_skip_tree (fts, ent); + return RM_ERROR; + } + } + } + + { + Ternary is_empty_directory; + enum RM_status s = prompt (fts, ent, true /*is_dir*/, x, + PA_DESCEND_INTO_DIR, &is_empty_directory); + + if (s == RM_OK && is_empty_directory == T_YES) + { + /* When we know (from prompt when in interactive mode) + that this is an empty directory, don't prompt twice. */ + s = excise (fts, ent, x, true); + fts_skip_tree (fts, ent); + } + + if (s != RM_OK) + { + mark_ancestor_dirs (ent); + fts_skip_tree (fts, ent); + } + + return s; + } + + case FTS_F: /* regular file */ + case FTS_NS: /* stat(2) failed */ + case FTS_SL: /* symbolic link */ + case FTS_SLNONE: /* symbolic link without target */ + case FTS_DP: /* postorder directory */ + case FTS_DNR: /* unreadable directory */ + case FTS_NSOK: /* e.g., dangling symlink */ + case FTS_DEFAULT: /* none of the above */ + { + /* With --one-file-system, do not attempt to remove a mount point. + fts' FTS_XDEV ensures that we don't process any entries under + the mount point. */ + if (ent->fts_info == FTS_DP + && x->one_file_system + && FTS_ROOTLEVEL < ent->fts_level + && ent->fts_statp->st_dev != fts->fts_dev) + { + mark_ancestor_dirs (ent); + error (0, 0, _("skipping %s, since it's on a different device"), + quoteaf (ent->fts_path)); + return RM_ERROR; + } + + bool is_dir = ent->fts_info == FTS_DP || ent->fts_info == FTS_DNR; + enum RM_status s = prompt (fts, ent, is_dir, x, PA_REMOVE_DIR, NULL); + if (s != RM_OK) + return s; + return excise (fts, ent, x, is_dir); + } + + case FTS_DC: /* directory that causes cycles */ + emit_cycle_warning (ent->fts_path); + fts_skip_tree (fts, ent); + return RM_ERROR; + + case FTS_ERR: + /* Various failures, from opendir to ENOMEM, to failure to "return" + to preceding directory, can provoke this. */ + error (0, ent->fts_errno, _("traversal failed: %s"), + quotef (ent->fts_path)); + fts_skip_tree (fts, ent); + return RM_ERROR; + + default: + error (0, 0, _("unexpected failure: fts_info=%d: %s\n" + "please report to %s"), + ent->fts_info, + quotef (ent->fts_path), + PACKAGE_BUGREPORT); + abort (); + } +} + +/* Remove FILEs, honoring options specified via X. + Return RM_OK if successful. */ +enum RM_status +rm (char *const *file, struct rm_options const *x) +{ + enum RM_status rm_status = RM_OK; + + if (*file) + { + int bit_flags = (FTS_CWDFD + | FTS_NOSTAT + | FTS_PHYSICAL); + + if (x->one_file_system) + bit_flags |= FTS_XDEV; + + FTS *fts = xfts_open (file, bit_flags, NULL); + + while (1) + { + FTSENT *ent; + + ent = fts_read (fts); + if (ent == NULL) + { + if (errno != 0) + { + error (0, errno, _("fts_read failed")); + rm_status = RM_ERROR; + } + break; + } + + enum RM_status s = rm_fts (fts, ent, x); + + assert (VALID_STATUS (s)); + UPDATE_STATUS (rm_status, s); + } + + if (fts_close (fts) != 0) + { + error (0, errno, _("fts_close failed")); + rm_status = RM_ERROR; + } + } + + return rm_status; +} |