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systemd/backport-CVE-2021-3997-rm-rf-refactor-rm_rf_children-split-out-body-of-dire.patch

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From ca4a0e7d41f0b2a1fe2f99dbc3763187c16cf7ab Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Tue, 26 Jan 2021 16:30:06 +0100
Subject: [PATCH] rm-rf: refactor rm_rf_children(), split out body of directory
iteration loop
This splits out rm_rf_children_inner() as body of the loop. We can use
that to implement rm_rf_child() for deleting one specific entry in a
directory.
(cherry picked from commit 1f0fb7d544711248cba34615e43c5a76bc902d74)
Conflict:NA
Reference:https://github.com/systemd/systemd/commit/ca4a0e7d41f0b2a1fe2f99dbc3763187c16cf7ab
---
src/shared/rm-rf.c | 223 ++++++++++++++++++++++++++-------------------
src/shared/rm-rf.h | 3 +-
2 files changed, 131 insertions(+), 95 deletions(-)
diff --git a/src/shared/rm-rf.c b/src/shared/rm-rf.c
index 900a7fb5ff..dffb9cf6ee 100644
--- a/src/shared/rm-rf.c
+++ b/src/shared/rm-rf.c
@@ -19,6 +19,9 @@
#include "stat-util.h"
#include "string-util.h"
+/* We treat tmpfs/ramfs + cgroupfs as non-physical file sytems. 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_cgroup_fs(sfs);
}
@@ -113,133 +116,145 @@ int fstatat_harder(int dfd,
return 0;
}
-int rm_rf_children(int fd, RemoveFlags flags, struct stat *root_dev) {
- _cleanup_closedir_ DIR *d = NULL;
- struct dirent *de;
- int ret = 0, r;
- struct statfs sfs;
+static int rm_rf_children_inner(
+ int fd,
+ const char *fname,
+ int is_dir,
+ RemoveFlags flags,
+ const struct stat *root_dev) {
- assert(fd >= 0);
+ struct stat st;
+ int r;
- /* 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.. */
+ assert(fd >= 0);
+ assert(fname);
- if (!(flags & REMOVE_PHYSICAL)) {
+ if (is_dir < 0 || (is_dir > 0 && (root_dev || (flags & REMOVE_SUBVOLUME)))) {
- r = fstatfs(fd, &sfs);
- if (r < 0) {
- safe_close(fd);
- return -errno;
- }
+ r = fstatat_harder(fd, fname, &st, AT_SYMLINK_NOFOLLOW, flags);
+ if (r < 0)
+ return r;
- 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;
+ is_dir = S_ISDIR(st.st_mode);
+ }
- (void) fd_get_path(fd, &path);
- log_error("Attempted to remove disk file system under \"%s\", and we can't allow that.",
- strna(path));
+ if (is_dir) {
+ _cleanup_close_ int subdir_fd = -1;
+ int q;
- safe_close(fd);
- return -EPERM;
- }
- }
+ /* if root_dev is set, remove subdirectories only if device is same */
+ if (root_dev && st.st_dev != root_dev->st_dev)
+ return 0;
- d = fdopendir(fd);
- if (!d) {
- safe_close(fd);
- return errno == ENOENT ? 0 : -errno;
- }
+ /* Stop at mount points */
+ r = fd_is_mount_point(fd, fname, 0);
+ if (r < 0)
+ return r;
+ if (r > 0)
+ return 0;
- FOREACH_DIRENT_ALL(de, d, return -errno) {
- bool is_dir;
- struct stat st;
+ if ((flags & REMOVE_SUBVOLUME) && btrfs_might_be_subvol(&st)) {
- if (dot_or_dot_dot(de->d_name))
- continue;
+ /* This could be a subvolume, try to remove it */
- if (de->d_type == DT_UNKNOWN ||
- (de->d_type == DT_DIR && (root_dev || (flags & REMOVE_SUBVOLUME)))) {
- r = fstatat_harder(fd, de->d_name, &st, AT_SYMLINK_NOFOLLOW, flags);
+ r = btrfs_subvol_remove_fd(fd, fname, BTRFS_REMOVE_RECURSIVE|BTRFS_REMOVE_QUOTA);
if (r < 0) {
- if (ret == 0 && r != -ENOENT)
- ret = r;
- continue;
- }
+ if (!IN_SET(r, -ENOTTY, -EINVAL))
+ return r;
- is_dir = S_ISDIR(st.st_mode);
- } else
- is_dir = de->d_type == DT_DIR;
+ /* ENOTTY, then it wasn't a btrfs subvolume, continue below. */
+ } else
+ /* It was a subvolume, done. */
+ return 1;
+ }
- if (is_dir) {
- _cleanup_close_ int subdir_fd = -1;
+ subdir_fd = openat(fd, fname, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME);
+ if (subdir_fd < 0)
+ return -errno;
- /* if root_dev is set, remove subdirectories only if device is same */
- if (root_dev && st.st_dev != root_dev->st_dev)
- continue;
+ /* 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);
- subdir_fd = openat(fd, de->d_name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|O_NOFOLLOW|O_NOATIME);
- if (subdir_fd < 0) {
- if (ret == 0 && errno != ENOENT)
- ret = -errno;
- continue;
- }
+ r = unlinkat_harder(fd, fname, AT_REMOVEDIR, flags);
+ if (r < 0)
+ return r;
+ if (q < 0)
+ return q;
- /* Stop at mount points */
- r = fd_is_mount_point(fd, de->d_name, 0);
- if (r < 0) {
- if (ret == 0 && r != -ENOENT)
- ret = r;
+ return 1;
- continue;
- }
- if (r > 0)
- continue;
+ } else if (!(flags & REMOVE_ONLY_DIRECTORIES)) {
+ r = unlinkat_harder(fd, fname, 0, flags);
+ if (r < 0)
+ return r;
- if ((flags & REMOVE_SUBVOLUME) && btrfs_might_be_subvol(&st)) {
+ return 1;
+ }
- /* This could be a subvolume, try to remove it */
+ return 0;
+}
- r = btrfs_subvol_remove_fd(fd, de->d_name, BTRFS_REMOVE_RECURSIVE|BTRFS_REMOVE_QUOTA);
- if (r < 0) {
- if (!IN_SET(r, -ENOTTY, -EINVAL)) {
- if (ret == 0)
- ret = r;
+int rm_rf_children(
+ int fd,
+ RemoveFlags flags,
+ const struct stat *root_dev) {
- continue;
- }
+ _cleanup_closedir_ DIR *d = NULL;
+ struct dirent *de;
+ int ret = 0, r;
- /* ENOTTY, then it wasn't a btrfs subvolume, continue below. */
- } else
- /* It was a subvolume, continue. */
- continue;
- }
+ assert(fd >= 0);
+
+ /* 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. */
+
+ d = fdopendir(fd);
+ if (!d) {
+ safe_close(fd);
+ return -errno;
+ }
- /* We pass REMOVE_PHYSICAL here, to avoid doing the fstatfs() to check the file
- * system type again for each directory */
- r = rm_rf_children(TAKE_FD(subdir_fd), flags | REMOVE_PHYSICAL, root_dev);
- if (r < 0 && ret == 0)
- ret = r;
+ if (!(flags & REMOVE_PHYSICAL)) {
+ struct statfs sfs;
- r = unlinkat_harder(fd, de->d_name, AT_REMOVEDIR, flags);
- if (r < 0 && r != -ENOENT && ret == 0)
- ret = r;
+ if (fstatfs(dirfd(d), &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. */
- } else if (!(flags & REMOVE_ONLY_DIRECTORIES)) {
+ _cleanup_free_ char *path = NULL;
- r = unlinkat_harder(fd, de->d_name, 0, flags);
- if (r < 0 && r != -ENOENT && ret == 0)
- ret = r;
+ (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_children_inner(dirfd(d), de->d_name, is_dir, flags, root_dev);
+ if (r < 0 && r != -ENOENT && ret == 0)
+ ret = r;
+ }
+
return ret;
}
int rm_rf(const char *path, RemoveFlags flags) {
int fd, r;
- struct statfs s;
assert(path);
@@ -284,9 +299,10 @@ int rm_rf(const char *path, RemoveFlags flags) {
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.",
@@ -314,3 +330,22 @@ int rm_rf(const char *path, RemoveFlags flags) {
return r;
}
+
+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_children_inner(fd, name, -1, flags, NULL);
+}
diff --git a/src/shared/rm-rf.h b/src/shared/rm-rf.h
index 40f0894c96..577a2795e0 100644
--- a/src/shared/rm-rf.h
+++ b/src/shared/rm-rf.h
@@ -23,7 +23,8 @@ int fstatat_harder(int dfd,
int fstatat_flags,
RemoveFlags remove_flags);
-int rm_rf_children(int fd, RemoveFlags flags, struct stat *root_dev);
+int rm_rf_children(int fd, RemoveFlags flags, const struct stat *root_dev);
+int rm_rf_child(int fd, const char *name, RemoveFlags flags);
int rm_rf(const char *path, RemoveFlags flags);
/* Useful for usage with _cleanup_(), destroys a directory and frees the pointer */
--
2.33.0
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