shaba/systemd
1
0
Fork 0
mirror of https://github.com/systemd/systemd.git synced 2025-02-27 01:57:35 +03:00
Code

basic: add fds_are_same_mount() helper

Browse Source
This commit is contained in:
Luca Boccassi 2023-12-05 15:32:30 +00:00
parent 26522a66a3
commit 5134e54625
3 changed files with 59 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

67
src/basic/fd-util.c
View File

@ -900,10 +900,7 @@ int fd_get_diskseq(int fd, uint64_t *ret) {
}
int path_is_root_at(int dir_fd, const char *path) {
STRUCT_NEW_STATX_DEFINE(st);
STRUCT_NEW_STATX_DEFINE(pst);
_cleanup_close_ int fd = -EBADF;
int r;
_cleanup_close_ int fd = -EBADF, pfd = -EBADF;
assert(dir_fd >= 0 || dir_fd == AT_FDCWD);
@ -915,19 +912,9 @@ int path_is_root_at(int dir_fd, const char *path) {
dir_fd = fd;
}
r = statx_fallback(dir_fd, ".", 0, STATX_TYPE|STATX_INO|STATX_MNT_ID, &st.sx);
if (r == -ENOTDIR)
return false;
if (r < 0)
return r;
r = statx_fallback(dir_fd, "..", 0, STATX_TYPE|STATX_INO|STATX_MNT_ID, &pst.sx);
if (r < 0)
return r;
/* First, compare inode. If these are different, the fd does not point to the root directory "/". */
if (!statx_inode_same(&st.sx, &pst.sx))
return false;
pfd = openat(dir_fd, "..", O_PATH|O_DIRECTORY|O_CLOEXEC);
if (pfd < 0)
return errno == ENOTDIR ? false : -errno;
/* Even if the parent directory has the same inode, the fd may not point to the root directory "/",
* and we also need to check that the mount ids are the same. Otherwise, a construct like the
@ -935,40 +922,64 @@ int path_is_root_at(int dir_fd, const char *path) {
*
* $ mkdir /tmp/x /tmp/x/y
* $ mount --bind /tmp/x /tmp/x/y
*
* Note, statx() does not provide the mount ID and path_get_mnt_id_at() does not work when an old
*/
return fds_are_same_mount(dir_fd, pfd);
}
int fds_are_same_mount(int fd1, int fd2) {
STRUCT_NEW_STATX_DEFINE(st1);
STRUCT_NEW_STATX_DEFINE(st2);
int r;
assert(fd1 >= 0);
assert(fd2 >= 0);
r = statx_fallback(fd1, "", AT_EMPTY_PATH, STATX_TYPE|STATX_INO|STATX_MNT_ID, &st1.sx);
if (r < 0)
return r;
r = statx_fallback(fd2, "", AT_EMPTY_PATH, STATX_TYPE|STATX_INO|STATX_MNT_ID, &st2.sx);
if (r < 0)
return r;
/* First, compare inode. If these are different, the fd does not point to the root directory "/". */
if (!statx_inode_same(&st1.sx, &st2.sx))
return false;
/* Note, statx() does not provide the mount ID and path_get_mnt_id_at() does not work when an old
* kernel is used. In that case, let's assume that we do not have such spurious mount points in an
* early boot stage, and silently skip the following check. */
if (!FLAGS_SET(st.nsx.stx_mask, STATX_MNT_ID)) {
if (!FLAGS_SET(st1.nsx.stx_mask, STATX_MNT_ID)) {
int mntid;
r = path_get_mnt_id_at_fallback(dir_fd, "", &mntid);
r = path_get_mnt_id_at_fallback(fd1, "", &mntid);
if (ERRNO_IS_NEG_NOT_SUPPORTED(r))
return true; /* skip the mount ID check */
if (r < 0)
return r;
assert(mntid >= 0);
st.nsx.stx_mnt_id = mntid;
st.nsx.stx_mask |= STATX_MNT_ID;
st1.nsx.stx_mnt_id = mntid;
st1.nsx.stx_mask |= STATX_MNT_ID;
}
if (!FLAGS_SET(pst.nsx.stx_mask, STATX_MNT_ID)) {
if (!FLAGS_SET(st2.nsx.stx_mask, STATX_MNT_ID)) {
int mntid;
r = path_get_mnt_id_at_fallback(dir_fd, "..", &mntid);
r = path_get_mnt_id_at_fallback(fd2, "", &mntid);
if (ERRNO_IS_NEG_NOT_SUPPORTED(r))
return true; /* skip the mount ID check */
if (r < 0)
return r;
assert(mntid >= 0);
pst.nsx.stx_mnt_id = mntid;
pst.nsx.stx_mask |= STATX_MNT_ID;
st2.nsx.stx_mnt_id = mntid;
st2.nsx.stx_mask |= STATX_MNT_ID;
}
return statx_mount_same(&st.nsx, &pst.nsx);
return statx_mount_same(&st1.nsx, &st2.nsx);
}
const char *accmode_to_string(int flags) {

2
src/basic/fd-util.h
View File

@ -117,6 +117,8 @@ static inline int dir_fd_is_root_or_cwd(int dir_fd) {
return dir_fd == AT_FDCWD ? true : path_is_root_at(dir_fd, NULL);
}
int fds_are_same_mount(int fd1, int fd2);
/* The maximum length a buffer for a /proc/self/fd/<fd> path needs */
#define PROC_FD_PATH_MAX \
(STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int))

18
src/test/test-fd-util.c
View File

@ -646,6 +646,24 @@ TEST(dir_fd_is_root) {
assert_se(dir_fd_is_root_or_cwd(fd) == 0);
}
TEST(fds_are_same_mount) {
_cleanup_close_ int fd1 = -EBADF, fd2 = -EBADF, fd3 = -EBADF, fd4 = -EBADF;
fd1 = open("/sys", O_CLOEXEC|O_PATH|O_DIRECTORY|O_NOFOLLOW);
fd2 = open("/proc", O_CLOEXEC|O_PATH|O_DIRECTORY|O_NOFOLLOW);
fd3 = open("/proc", O_CLOEXEC|O_PATH|O_DIRECTORY|O_NOFOLLOW);
fd4 = open("/", O_CLOEXEC|O_PATH|O_DIRECTORY|O_NOFOLLOW);
if (fd1 < 0 || fd2 < 0 || fd3 < 0 || fd4 < 0)
return (void) log_tests_skipped_errno(errno, "Failed to open /sys or /proc or /");
if (fds_are_same_mount(fd1, fd4) > 0 && fds_are_same_mount(fd2, fd4) > 0)
return (void) log_tests_skipped("Cannot test fds_are_same_mount() as /sys and /proc are not mounted");
assert_se(fds_are_same_mount(fd1, fd2) == 0);
assert_se(fds_are_same_mount(fd2, fd3) > 0);
}
TEST(fd_get_path) {
_cleanup_(rm_rf_physical_and_freep) char *t = NULL;
_cleanup_close_ int tfd = -EBADF, fd = -EBADF;