src/basic/rm-rf.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <fcntl.h>
   5 #include <stdbool.h>
   6 #include <stddef.h>
   7 #include <unistd.h>
   8
   9 #include "alloc-util.h"
  10 #include "btrfs-util.h"
  11 #include "cgroup-util.h"
  12 #include "dirent-util.h"
  13 #include "fd-util.h"
  14 #include "log.h"
  15 #include "macro.h"
  16 #include "mountpoint-util.h"
  17 #include "path-util.h"
  18 #include "rm-rf.h"
  19 #include "stat-util.h"
  20 #include "string-util.h"
  21
  22 static bool is_physical_fs(const struct statfs *sfs) {
  23         return !is_temporary_fs(sfs) && !is_cgroup_fs(sfs);
  24 }
  25
  26 static int unlinkat_harder(
  27                 int dfd,
  28                 const char *filename,
  29                 int unlink_flags,
  30                 RemoveFlags remove_flags) {
  31
  32         struct stat st;
  33         int r;
  34
  35         /* Like unlinkat(), but tries harder: if we get EACCESS we'll try to set the r/w/x bits on the
  36          * directory. This is useful if we run unprivileged and have some files where the w bit is
  37          * missing. */
  38
  39         if (unlinkat(dfd, filename, unlink_flags) >= 0)
  40                 return 0;
  41         if (errno != EACCES || !FLAGS_SET(remove_flags, REMOVE_CHMOD))
  42                 return -errno;
  43
  44         if (fstat(dfd, &st) < 0)
  45                 return -errno;
  46         if (!S_ISDIR(st.st_mode))
  47                 return -ENOTDIR;
  48         if (FLAGS_SET(st.st_mode, 0700)) /* Already set? */
  49                 return -EACCES; /* original error */
  50         if (st.st_uid != geteuid())  /* this only works if the UID matches ours */
  51                 return -EACCES;
  52
  53         if (fchmod(dfd, (st.st_mode | 0700) & 07777) < 0)
  54                 return -errno;
  55
  56         if (unlinkat(dfd, filename, unlink_flags) < 0) {
  57                 r = -errno;
  58                 /* Try to restore the original access mode if this didn't work */
  59                 (void) fchmod(dfd, st.st_mode & 07777);
  60                 return r;
  61         }
  62
  63         return 0;
  64 }
  65
  66 int rm_rf_children(int fd, RemoveFlags flags, struct stat *root_dev) {
  67         _cleanup_closedir_ DIR *d = NULL;
  68         struct dirent *de;
  69         int ret = 0, r;
  70         struct statfs sfs;
  71
  72         assert(fd >= 0);
  73
  74         /* This returns the first error we run into, but nevertheless tries to go on. This closes the passed
  75          * fd, in all cases, including on failure.. */
  76
  77         if (!(flags & REMOVE_PHYSICAL)) {
  78
  79                 r = fstatfs(fd, &sfs);
  80                 if (r < 0) {
  81                         safe_close(fd);
  82                         return -errno;
  83                 }
  84
  85                 if (is_physical_fs(&sfs)) {
  86                         /* We refuse to clean physical file systems with this call,
  87                          * unless explicitly requested. This is extra paranoia just
  88                          * to be sure we never ever remove non-state data. */
  89                         _cleanup_free_ char *path = NULL;
  90
  91                         (void) fd_get_path(fd, &path);
  92                         log_error("Attempted to remove disk file system under \"%s\", and we can't allow that.",
  93                                   strna(path));
  94
  95                         safe_close(fd);
  96                         return -EPERM;
  97                 }
  98         }
  99
 100         d = fdopendir(fd);
 101         if (!d) {
 102                 safe_close(fd);
 103                 return errno == ENOENT ? 0 : -errno;
 104         }
 105
 106         FOREACH_DIRENT_ALL(de, d, return -errno) {
 107                 bool is_dir;
 108                 struct stat st;
 109
 110                 if (dot_or_dot_dot(de->d_name))
 111                         continue;
 112
 113                 if (de->d_type == DT_UNKNOWN ||
 114                     (de->d_type == DT_DIR && (root_dev || (flags & REMOVE_SUBVOLUME)))) {
 115                         if (fstatat(fd, de->d_name, &st, AT_SYMLINK_NOFOLLOW) < 0) {
 116                                 if (ret == 0 && errno != ENOENT)
 117                                         ret = -errno;
 118                                 continue;
 119                         }
 120
 121                         is_dir = S_ISDIR(st.st_mode);
 122                 } else
 123                         is_dir = de->d_type == DT_DIR;
 124
 125                 if (is_dir) {
 126                         _cleanup_close_ int subdir_fd = -1;
 127
 128                         /* if root_dev is set, remove subdirectories only if device is same */
 129                         if (root_dev && st.st_dev != root_dev->st_dev)
 130                                 continue;
 131
 132                         subdir_fd = openat(fd, de->d_name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME);
 133                         if (subdir_fd < 0) {
 134                                 if (ret == 0 && errno != ENOENT)
 135                                         ret = -errno;
 136                                 continue;
 137                         }
 138
 139                         /* Stop at mount points */
 140                         r = fd_is_mount_point(fd, de->d_name, 0);
 141                         if (r < 0) {
 142                                 if (ret == 0 && r != -ENOENT)
 143                                         ret = r;
 144
 145                                 continue;
 146                         }
 147                         if (r > 0)
 148                                 continue;
 149
 150                         if ((flags & REMOVE_SUBVOLUME) && st.st_ino == 256) {
 151
 152                                 /* This could be a subvolume, try to remove it */
 153
 154                                 r = btrfs_subvol_remove_fd(fd, de->d_name, BTRFS_REMOVE_RECURSIVE|BTRFS_REMOVE_QUOTA);
 155                                 if (r < 0) {
 156                                         if (!IN_SET(r, -ENOTTY, -EINVAL)) {
 157                                                 if (ret == 0)
 158                                                         ret = r;
 159
 160                                                 continue;
 161                                         }
 162
 163                                         /* ENOTTY, then it wasn't a btrfs subvolume, continue below. */
 164                                 } else
 165                                         /* It was a subvolume, continue. */
 166                                         continue;
 167                         }
 168
 169                         /* We pass REMOVE_PHYSICAL here, to avoid doing the fstatfs() to check the file
 170                          * system type again for each directory */
 171                         r = rm_rf_children(TAKE_FD(subdir_fd), flags | REMOVE_PHYSICAL, root_dev);
 172                         if (r < 0 && ret == 0)
 173                                 ret = r;
 174
 175                         r = unlinkat_harder(fd, de->d_name, AT_REMOVEDIR, flags);
 176                         if (r < 0 && r != -ENOENT && ret == 0)
 177                                 ret = r;
 178
 179                 } else if (!(flags & REMOVE_ONLY_DIRECTORIES)) {
 180
 181                         r = unlinkat_harder(fd, de->d_name, 0, flags);
 182                         if (r < 0 && r != -ENOENT && ret == 0)
 183                                 ret = r;
 184                 }
 185         }
 186         return ret;
 187 }
 188
 189 int rm_rf(const char *path, RemoveFlags flags) {
 190         int fd, r;
 191         struct statfs s;
 192
 193         assert(path);
 194
 195         /* For now, don't support dropping subvols when also only dropping directories, since we can't do
 196          * this race-freely. */
 197         if (FLAGS_SET(flags, REMOVE_ONLY_DIRECTORIES|REMOVE_SUBVOLUME))
 198                 return -EINVAL;
 199
 200         /* We refuse to clean the root file system with this call. This is extra paranoia to never cause a
 201          * really seriously broken system. */
 202         if (path_equal_or_files_same(path, "/", AT_SYMLINK_NOFOLLOW))
 203                 return log_error_errno(SYNTHETIC_ERRNO(EPERM),
 204                                        "Attempted to remove entire root file system (\"%s\"), and we can't allow that.",
 205                                        path);
 206
 207         if (FLAGS_SET(flags, REMOVE_SUBVOLUME | REMOVE_ROOT | REMOVE_PHYSICAL)) {
 208                 /* Try to remove as subvolume first */
 209                 r = btrfs_subvol_remove(path, BTRFS_REMOVE_RECURSIVE|BTRFS_REMOVE_QUOTA);
 210                 if (r >= 0)
 211                         return r;
 212
 213                 if (FLAGS_SET(flags, REMOVE_MISSING_OK) && r == -ENOENT)
 214                         return 0;
 215
 216                 if (!IN_SET(r, -ENOTTY, -EINVAL, -ENOTDIR))
 217                         return r;
 218
 219                 /* Not btrfs or not a subvolume */
 220         }
 221
 222         fd = open(path, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME);
 223         if (fd < 0) {
 224                 if (FLAGS_SET(flags, REMOVE_MISSING_OK) && errno == ENOENT)
 225                         return 0;
 226
 227                 if (!IN_SET(errno, ENOTDIR, ELOOP))
 228                         return -errno;
 229
 230                 if (FLAGS_SET(flags, REMOVE_ONLY_DIRECTORIES))
 231                         return 0;
 232
 233                 if (FLAGS_SET(flags, REMOVE_ROOT)) {
 234
 235                         if (!FLAGS_SET(flags, REMOVE_PHYSICAL)) {
 236                                 if (statfs(path, &s) < 0)
 237                                         return -errno;
 238
 239                                 if (is_physical_fs(&s))
 240                                         return log_error_errno(SYNTHETIC_ERRNO(EPERM),
 241                                                                "Attempted to remove files from a disk file system under \"%s\", refusing.",
 242                                                                path);
 243                         }
 244
 245                         if (unlink(path) < 0) {
 246                                 if (FLAGS_SET(flags, REMOVE_MISSING_OK) && errno == ENOENT)
 247                                         return 0;
 248
 249                                 return -errno;
 250                         }
 251                 }
 252
 253                 return 0;
 254         }
 255
 256         r = rm_rf_children(fd, flags, NULL);
 257
 258         if (FLAGS_SET(flags, REMOVE_ROOT) &&
 259             rmdir(path) < 0 &&
 260             r >= 0 &&
 261             (!FLAGS_SET(flags, REMOVE_MISSING_OK) || errno != ENOENT))
 262                 r = -errno;
 263
 264         return r;
 265 }