From 3bac86abfa1b1720180840ffb9d06b3d54841c11 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= Date: Tue, 23 Nov 2021 15:55:45 +0100 Subject: [PATCH 1/3] shared/rm_rf: refactor rm_rf_children_inner() to shorten code a bit --- src/shared/rm-rf.c | 27 +++++++++------------------ 1 file changed, 9 insertions(+), 18 deletions(-) diff --git a/src/shared/rm-rf.c b/src/shared/rm-rf.c index fd54b2ccaf9..6dbdc648eae 100644 --- a/src/shared/rm-rf.c +++ b/src/shared/rm-rf.c @@ -124,7 +124,7 @@ static int rm_rf_children_inner( const struct stat *root_dev) { struct stat st; - int r; + int r, q = 0; assert(fd >= 0); assert(fname); @@ -142,7 +142,6 @@ static int rm_rf_children_inner( if (is_dir) { _cleanup_close_ int subdir_fd = -1; - int q; /* if root_dev is set, remove subdirectories only if device is same */ if (root_dev && st.st_dev != root_dev->st_dev) @@ -178,23 +177,15 @@ static int rm_rf_children_inner( * again for each directory */ q = rm_rf_children(TAKE_FD(subdir_fd), flags | REMOVE_PHYSICAL, root_dev); - r = unlinkat_harder(fd, fname, AT_REMOVEDIR, flags); - if (r < 0) - return r; - if (q < 0) - return q; + } else if (flags & REMOVE_ONLY_DIRECTORIES) + return 0; - return 1; - - } else if (!(flags & REMOVE_ONLY_DIRECTORIES)) { - r = unlinkat_harder(fd, fname, 0, flags); - if (r < 0) - return r; - - return 1; - } - - 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; } int rm_rf_children( From 84ced330020c0bae57bd4628f1f44eec91304e69 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= Date: Tue, 23 Nov 2021 16:56:42 +0100 Subject: [PATCH 2/3] shared/rm_rf: refactor rm_rf() to shorten code a bit --- src/shared/rm-rf.c | 53 ++++++++++++++++++++-------------------------- 1 file changed, 23 insertions(+), 30 deletions(-) diff --git a/src/shared/rm-rf.c b/src/shared/rm-rf.c index 6dbdc648eae..48fdf083484 100644 --- a/src/shared/rm-rf.c +++ b/src/shared/rm-rf.c @@ -249,7 +249,7 @@ int rm_rf_children( } int rm_rf(const char *path, RemoveFlags flags) { - int fd, r; + int fd, r, q = 0; assert(path); @@ -281,49 +281,42 @@ int rm_rf(const char *path, RemoveFlags flags) { } fd = open(path, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME); - if (fd < 0) { + if (fd >= 0) { + /* We have a dir */ + r = rm_rf_children(fd, flags, NULL); + + if (FLAGS_SET(flags, REMOVE_ROOT)) + q = RET_NERRNO(rmdir(path)); + } else { if (FLAGS_SET(flags, REMOVE_MISSING_OK) && errno == ENOENT) return 0; if (!IN_SET(errno, ENOTDIR, ELOOP)) return -errno; - if (FLAGS_SET(flags, REMOVE_ONLY_DIRECTORIES)) + if (FLAGS_SET(flags, REMOVE_ONLY_DIRECTORIES) || !FLAGS_SET(flags, REMOVE_ROOT)) return 0; - if (FLAGS_SET(flags, REMOVE_ROOT)) { - - if (!FLAGS_SET(flags, REMOVE_PHYSICAL)) { - struct statfs s; - - if (statfs(path, &s) < 0) - return -errno; - 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); - } - - if (unlink(path) < 0) { - if (FLAGS_SET(flags, REMOVE_MISSING_OK) && errno == ENOENT) - return 0; + if (!FLAGS_SET(flags, REMOVE_PHYSICAL)) { + struct statfs s; + if (statfs(path, &s) < 0) return -errno; - } + 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); } - return 0; + r = 0; + q = RET_NERRNO(unlink(path)); } - r = rm_rf_children(fd, flags, NULL); - - if (FLAGS_SET(flags, REMOVE_ROOT) && - rmdir(path) < 0 && - r >= 0 && - (!FLAGS_SET(flags, REMOVE_MISSING_OK) || errno != ENOENT)) - r = -errno; - - return r; + 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) { From 5b1cf7a9be37e20133c0208005274ce4a5b5c6a1 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Zbigniew=20J=C4=99drzejewski-Szmek?= Date: Tue, 30 Nov 2021 22:29:05 +0100 Subject: [PATCH 3/3] shared/rm-rf: loop over nested directories instead of instead of recursing To remove directory structures, we need to remove the innermost items first, and then recursively remove higher-level directories. We would recursively descend into directories and invoke rm_rf_children and rm_rm_children_inner. This is problematic when too many directories are nested. Instead, let's create a "TODO" queue. In the the queue, for each level we hold the DIR* object we were working on, and the name of the directory. This allows us to leave a partially-processed directory, and restart the removal loop one level down. When done with the inner directory, we use the name to unlinkat() it from the parent, and proceed with the removal of other items. Because the nesting is increased by one level, it is best to view this patch with -b/--ignore-space-change. This fixes CVE-2021-3997, https://bugzilla.redhat.com/show_bug.cgi?id=2024639. The issue was reported and patches reviewed by Qualys Team. Mauro Matteo Cascella and Riccardo Schirone from Red Hat handled the disclosure. --- src/shared/rm-rf.c | 165 +++++++++++++++++++++++++++++++-------------- 1 file changed, 115 insertions(+), 50 deletions(-) diff --git a/src/shared/rm-rf.c b/src/shared/rm-rf.c index 48fdf083484..6cc4265737b 100644 --- a/src/shared/rm-rf.c +++ b/src/shared/rm-rf.c @@ -52,7 +52,6 @@ static int patch_dirfd_mode( } int unlinkat_harder(int dfd, const char *filename, int unlink_flags, RemoveFlags remove_flags) { - mode_t old_mode; int r; @@ -116,12 +115,13 @@ int fstatat_harder(int dfd, return 0; } -static int rm_rf_children_inner( +static int rm_rf_inner_child( int fd, const char *fname, int is_dir, RemoveFlags flags, - const struct stat *root_dev) { + const struct stat *root_dev, + bool allow_recursion) { struct stat st; int r, q = 0; @@ -141,9 +141,7 @@ static int rm_rf_children_inner( } if (is_dir) { - _cleanup_close_ int subdir_fd = -1; - - /* if root_dev is set, remove subdirectories only if device is same */ + /* If root_dev is set, remove subdirectories only if device is same */ if (root_dev && st.st_dev != root_dev->st_dev) return 0; @@ -155,7 +153,6 @@ static int rm_rf_children_inner( return 0; if ((flags & REMOVE_SUBVOLUME) && btrfs_might_be_subvol(&st)) { - /* This could be a subvolume, try to remove it */ r = btrfs_subvol_remove_fd(fd, fname, BTRFS_REMOVE_RECURSIVE|BTRFS_REMOVE_QUOTA); @@ -169,13 +166,16 @@ static int rm_rf_children_inner( return 1; } - subdir_fd = openat(fd, fname, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME); + if (!allow_recursion) + return -EISDIR; + + int subdir_fd = openat(fd, fname, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME); if (subdir_fd < 0) return -errno; /* We pass REMOVE_PHYSICAL here, to avoid doing the fstatfs() to check the file system type * again for each directory */ - q = rm_rf_children(TAKE_FD(subdir_fd), flags | REMOVE_PHYSICAL, root_dev); + q = rm_rf_children(subdir_fd, flags | REMOVE_PHYSICAL, root_dev); } else if (flags & REMOVE_ONLY_DIRECTORIES) return 0; @@ -188,63 +188,128 @@ static int rm_rf_children_inner( return 1; } +typedef struct TodoEntry { + DIR *dir; /* A directory that we were operating on. */ + char *dirname; /* The filename of that directory itself. */ +} TodoEntry; + +static void free_todo_entries(TodoEntry **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) { - _cleanup_closedir_ DIR *d = NULL; + _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; - assert(fd >= 0); + /* Return the first error we run into, but nevertheless try to go on. + * The passed fd is closed in all cases, including on failure. */ - /* This returns the first error we run into, but nevertheless tries to go on. This closes the passed - * fd, in all cases, including on failure. */ + for (;;) { /* This loop corresponds to the directory nesting level. */ + _cleanup_closedir_ DIR *d = NULL; - d = fdopendir(fd); - if (!d) { - safe_close(fd); - return -errno; - } + 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 && ret == 0) + ret = r; + dirname = mfree(dirname); - if (!(flags & REMOVE_PHYSICAL)) { - struct statfs sfs; + /* 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); - if (fstatfs(dirfd(d), &sfs) < 0) - return -errno; + 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 (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. */ + if (!(flags & REMOVE_PHYSICAL)) { + struct statfs sfs; - _cleanup_free_ char *path = NULL; + if (fstatfs(fd, &sfs) < 0) + return -errno; - (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)); + 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(); + + int newfd = openat(fd, de->d_name, + O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME); + if (newfd >= 0) { + todos[n_todo++] = (TodoEntry) { TAKE_PTR(d), TAKE_PTR(dirname) }; + fd = newfd; + dirname = TAKE_PTR(newdirname); + + goto next_fd; + + } else if (errno != -ENOENT && ret == 0) + ret = -errno; + + } 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) + break; } - 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_children_inner(dirfd(d), de->d_name, is_dir, flags, root_dev); - if (r < 0 && r != -ENOENT && ret == 0) - ret = r; - } - - if (FLAGS_SET(flags, REMOVE_SYNCFS) && syncfs(dirfd(d)) < 0 && ret >= 0) - ret = -errno; - return ret; } @@ -335,5 +400,5 @@ int rm_rf_child(int fd, const char *name, RemoveFlags flags) { if (FLAGS_SET(flags, REMOVE_ONLY_DIRECTORIES|REMOVE_SUBVOLUME)) return -EINVAL; - return rm_rf_children_inner(fd, name, -1, flags, NULL); + return rm_rf_inner_child(fd, name, -1, flags, NULL, true); }