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fs-util: change chmod_and_chown() to not complain if stat data already matches 

Let's reduce the chance of failure: if we can't apply the chmod/chown
requested, check if it's applied anyway, and if so, supress the error.

This is even race-free since we operate on an O_PATH fd anyway.
This commit is contained in:
Lennart Poettering 2019-03-14 16:47:03 +01:00
parent 17b70256f2
commit 30ff18d8a2
1 changed files with 62 additions and 17 deletions
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79
src/basic/fs-util.c
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@ -215,64 +215,109 @@ int readlink_and_make_absolute(const char *p, char **r) {
int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) {
char fd_path[STRLEN("/proc/self/fd/") + DECIMAL_STR_MAX(int) + 1];
_cleanup_close_ int fd = -1;
bool st_valid = false;
struct stat st;
int r;
assert(path);
/* Under the assumption that we are running privileged we first change the access mode and only then hand out
* ownership to avoid a window where access is too open. */
/* Under the assumption that we are running privileged we first change the access mode and only then
* hand out ownership to avoid a window where access is too open. */
fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW); /* Let's acquire an O_PATH fd, as precaution to change mode/owner
* on the same file */
fd = open(path, O_PATH|O_CLOEXEC|O_NOFOLLOW); /* Let's acquire an O_PATH fd, as precaution to change
* mode/owner on the same file */
if (fd < 0)
return -errno;
xsprintf(fd_path, "/proc/self/fd/%i", fd);
if (mode != MODE_INVALID) {
if ((mode & S_IFMT) != 0) {
struct stat st;
if (stat(fd_path, &st) < 0)
return -errno;
if ((mode & S_IFMT) != (st.st_mode & S_IFMT))
return -EINVAL;
st_valid = true;
}
if (chmod(fd_path, mode & 07777) < 0)
return -errno;
if (chmod(fd_path, mode & 07777) < 0) {
r = -errno;
if (!st_valid && stat(fd_path, &st) < 0)
return -errno;
if ((mode & 07777) != (st.st_mode & 07777))
return r;
st_valid = true;
}
}
if (uid != UID_INVALID || gid != GID_INVALID)
if (chown(fd_path, uid, gid) < 0)
return -errno;
if (uid != UID_INVALID || gid != GID_INVALID) {
if (chown(fd_path, uid, gid) < 0) {
r = -errno;
if (!st_valid && stat(fd_path, &st) < 0)
return -errno;
if (uid != UID_INVALID && st.st_uid != uid)
return r;
if (gid != GID_INVALID && st.st_gid != gid)
return r;
}
}
return 0;
}
int fchmod_and_chown(int fd, mode_t mode, uid_t uid, gid_t gid) {
bool st_valid = false;
struct stat st;
int r;
/* Under the assumption that we are running privileged we first change the access mode and only then hand out
* ownership to avoid a window where access is too open. */
if (mode != MODE_INVALID) {
if ((mode & S_IFMT) != 0) {
struct stat st;
if (fstat(fd, &st) < 0)
return -errno;
if ((mode & S_IFMT) != (st.st_mode & S_IFMT))
return -EINVAL;
st_valid = true;
}
if (fchmod(fd, mode & 0777) < 0)
return -errno;
if (fchmod(fd, mode & 07777) < 0) {
r = -errno;
if (!st_valid && fstat(fd, &st) < 0)
return -errno;
if ((mode & 07777) != (st.st_mode & 07777))
return r;
st_valid = true;
}
}
if (uid != UID_INVALID || gid != GID_INVALID)
if (fchown(fd, uid, gid) < 0)
return -errno;
if (fchown(fd, uid, gid) < 0) {
r = -errno;
if (!st_valid && fstat(fd, &st) < 0)
return -errno;
if (uid != UID_INVALID && st.st_uid != uid)
return r;
if (gid != GID_INVALID && st.st_gid != gid)
return r;
}
return 0;
}