mirror of
https://github.com/morgan9e/systemd
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70554f7ebc
This carefully combines getxattr_at_malloc() and parse_bool(), which is something we use at multiple places.
380 lines
13 KiB
C
380 lines
13 KiB
C
/* SPDX-License-Identifier: LGPL-2.1-or-later */
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#include <errno.h>
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#include <fcntl.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <sys/time.h>
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#include <sys/xattr.h>
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#include "alloc-util.h"
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#include "errno-util.h"
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#include "fd-util.h"
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#include "macro.h"
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#include "missing_syscall.h"
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#include "parse-util.h"
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#include "sparse-endian.h"
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#include "stat-util.h"
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#include "stdio-util.h"
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#include "string-util.h"
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#include "time-util.h"
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#include "xattr-util.h"
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int getxattr_at_malloc(
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int fd,
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const char *path,
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const char *name,
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int flags,
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char **ret) {
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_cleanup_close_ int opened_fd = -EBADF;
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unsigned n_attempts = 7;
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bool by_procfs = false;
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size_t l = 100;
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assert(fd >= 0 || fd == AT_FDCWD);
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assert(name);
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assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
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assert(ret);
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/* So, this is single function that does what getxattr()/lgetxattr()/fgetxattr() does, but in one go,
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* and with additional bells and whistles. Specifically:
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*
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* 1. This works on O_PATH fds (which fgetxattr() does not)
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* 2. Provides full openat()-style semantics, i.e. by-fd, by-path and combination thereof
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* 3. As extension to openat()-style semantics implies AT_EMPTY_PATH if path is NULL.
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* 4. Does a malloc() loop, automatically sizing the allocation
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* 5. NUL-terminates the returned buffer (for safety)
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*/
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if (!path) /* If path is NULL, imply AT_EMPTY_PATH. – But if it's "", don't — for safety reasons. */
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flags |= AT_EMPTY_PATH;
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if (isempty(path)) {
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if (!FLAGS_SET(flags, AT_EMPTY_PATH))
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return -EINVAL;
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if (fd == AT_FDCWD) /* Both unspecified? Then operate on current working directory */
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path = ".";
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else
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path = NULL;
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} else if (fd != AT_FDCWD) {
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/* If both have been specified, then we go via O_PATH */
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opened_fd = openat(fd, path, O_PATH|O_CLOEXEC|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : O_NOFOLLOW));
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if (opened_fd < 0)
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return -errno;
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fd = opened_fd;
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path = NULL;
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by_procfs = true; /* fgetxattr() is not going to work, go via /proc/ link right-away */
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}
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for (;;) {
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_cleanup_free_ char *v = NULL;
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ssize_t n;
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if (n_attempts == 0) /* If someone is racing against us, give up eventually */
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return -EBUSY;
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n_attempts--;
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v = new0(char, l+1);
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if (!v)
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return -ENOMEM;
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l = MALLOC_ELEMENTSOF(v) - 1;
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if (path)
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n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? getxattr(path, name, v, l) : lgetxattr(path, name, v, l);
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else
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n = by_procfs ? getxattr(FORMAT_PROC_FD_PATH(fd), name, v, l) : fgetxattr(fd, name, v, l);
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if (n < 0) {
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if (errno == EBADF) {
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if (by_procfs || path)
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return -EBADF;
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by_procfs = true; /* Might be an O_PATH fd, try again via /proc/ link */
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continue;
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}
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if (errno != ERANGE)
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return -errno;
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} else {
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v[n] = 0; /* NUL terminate */
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*ret = TAKE_PTR(v);
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return (int) n;
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}
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if (path)
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n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? getxattr(path, name, NULL, 0) : lgetxattr(path, name, NULL, 0);
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else
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n = by_procfs ? getxattr(FORMAT_PROC_FD_PATH(fd), name, NULL, 0) : fgetxattr(fd, name, NULL, 0);
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if (n < 0)
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return -errno;
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if (n > INT_MAX) /* We couldn't return this as 'int' anymore */
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return -E2BIG;
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l = (size_t) n;
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}
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}
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int getxattr_at_bool(int fd, const char *path, const char *name, int flags) {
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_cleanup_free_ char *v = NULL;
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int r;
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r = getxattr_at_malloc(fd, path, name, flags, &v);
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if (r < 0)
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return r;
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if (memchr(v, 0, r)) /* Refuse embedded NUL byte */
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return -EINVAL;
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return parse_boolean(v);
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}
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static int parse_crtime(le64_t le, usec_t *usec) {
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uint64_t u;
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assert(usec);
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u = le64toh(le);
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if (IN_SET(u, 0, UINT64_MAX))
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return -EIO;
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*usec = (usec_t) u;
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return 0;
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}
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int fd_getcrtime_at(
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int fd,
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const char *path,
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int flags,
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usec_t *ret) {
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_cleanup_free_ le64_t *le = NULL;
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STRUCT_STATX_DEFINE(sx);
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usec_t a, b;
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int r;
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assert(fd >= 0 || fd == AT_FDCWD);
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assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
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assert(ret);
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if (!path)
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flags |= AT_EMPTY_PATH;
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/* So here's the deal: the creation/birth time (crtime/btime) of a file is a relatively newly supported concept
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* on Linux (or more strictly speaking: a concept that only recently got supported in the API, it was
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* implemented on various file systems on the lower level since a while, but never was accessible). However, we
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* needed a concept like that for vacuuming algorithms and such, hence we emulated it via a user xattr for a
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* long time. Starting with Linux 4.11 there's statx() which exposes the timestamp to userspace for the first
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* time, where it is available. This function will read it, but it tries to keep some compatibility with older
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* systems: we try to read both the crtime/btime and the xattr, and then use whatever is older. After all the
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* concept is useful for determining how "old" a file really is, and hence using the older of the two makes
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* most sense. */
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if (statx(fd, strempty(path),
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(flags & ~AT_SYMLINK_FOLLOW)|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : AT_SYMLINK_NOFOLLOW)|AT_STATX_DONT_SYNC,
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STATX_BTIME,
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&sx) >= 0 &&
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(sx.stx_mask & STATX_BTIME) &&
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sx.stx_btime.tv_sec != 0)
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a = (usec_t) sx.stx_btime.tv_sec * USEC_PER_SEC +
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(usec_t) sx.stx_btime.tv_nsec / NSEC_PER_USEC;
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else
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a = USEC_INFINITY;
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r = getxattr_at_malloc(fd, path, "user.crtime_usec", flags, (char**) &le);
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if (r >= 0) {
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if (r != sizeof(*le))
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r = -EIO;
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else
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r = parse_crtime(*le, &b);
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}
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if (r < 0) {
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if (a != USEC_INFINITY) {
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*ret = a;
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return 0;
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}
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return r;
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}
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if (a != USEC_INFINITY)
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*ret = MIN(a, b);
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else
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*ret = b;
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return 0;
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}
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int fd_setcrtime(int fd, usec_t usec) {
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le64_t le;
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assert(fd >= 0);
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if (!timestamp_is_set(usec))
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usec = now(CLOCK_REALTIME);
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le = htole64((uint64_t) usec);
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return RET_NERRNO(fsetxattr(fd, "user.crtime_usec", &le, sizeof(le), 0));
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}
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int listxattr_at_malloc(
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int fd,
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const char *path,
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int flags,
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char **ret) {
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_cleanup_close_ int opened_fd = -EBADF;
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bool by_procfs = false;
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unsigned n_attempts = 7;
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size_t l = 100;
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assert(fd >= 0 || fd == AT_FDCWD);
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assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
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assert(ret);
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/* This is to listxattr()/llistattr()/flistattr() what getxattr_at_malloc() is to getxattr()/… */
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if (!path) /* If path is NULL, imply AT_EMPTY_PATH. – But if it's "", don't. */
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flags |= AT_EMPTY_PATH;
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if (isempty(path)) {
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if (!FLAGS_SET(flags, AT_EMPTY_PATH))
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return -EINVAL;
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if (fd == AT_FDCWD) /* Both unspecified? Then operate on current working directory */
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path = ".";
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else
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path = NULL;
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} else if (fd != AT_FDCWD) {
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/* If both have been specified, then we go via O_PATH */
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opened_fd = openat(fd, path, O_PATH|O_CLOEXEC|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : O_NOFOLLOW));
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if (opened_fd < 0)
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return -errno;
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fd = opened_fd;
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path = NULL;
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by_procfs = true;
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}
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for (;;) {
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_cleanup_free_ char *v = NULL;
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ssize_t n;
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if (n_attempts == 0) /* If someone is racing against us, give up eventually */
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return -EBUSY;
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n_attempts--;
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v = new(char, l+1);
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if (!v)
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return -ENOMEM;
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l = MALLOC_ELEMENTSOF(v) - 1;
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if (path)
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n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? listxattr(path, v, l) : llistxattr(path, v, l);
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else
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n = by_procfs ? listxattr(FORMAT_PROC_FD_PATH(fd), v, l) : flistxattr(fd, v, l);
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if (n < 0) {
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if (errno == EBADF) {
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if (by_procfs || path)
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return -EBADF;
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by_procfs = true; /* Might be an O_PATH fd, try again via /proc/ link */
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continue;
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}
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if (errno != ERANGE)
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return -errno;
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} else {
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v[n] = 0; /* NUL terminate */
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*ret = TAKE_PTR(v);
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return (int) n;
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}
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if (path)
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n = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? listxattr(path, NULL, 0) : llistxattr(path, NULL, 0);
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else
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n = by_procfs ? listxattr(FORMAT_PROC_FD_PATH(fd), NULL, 0) : flistxattr(fd, NULL, 0);
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if (n < 0)
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return -errno;
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if (n > INT_MAX) /* We couldn't return this as 'int' anymore */
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return -E2BIG;
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l = (size_t) n;
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}
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}
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int xsetxattr(int fd,
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const char *path,
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const char *name,
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const char *value,
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size_t size,
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int flags) {
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_cleanup_close_ int opened_fd = -EBADF;
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bool by_procfs = false;
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int r;
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assert(fd >= 0 || fd == AT_FDCWD);
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assert(name);
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assert(value);
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assert((flags & ~(AT_SYMLINK_FOLLOW|AT_EMPTY_PATH)) == 0);
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/* So, this is a single function that does what setxattr()/lsetxattr()/fsetxattr() do, but in one go,
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* and with additional bells and whistles. Specifically:
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*
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* 1. This works on O_PATH fds (which fsetxattr() does not)
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* 2. Provides full openat()-style semantics, i.e. by-fd, by-path and combination thereof
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* 3. As extension to openat()-style semantics implies AT_EMPTY_PATH if path is NULL.
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*/
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if (!path) /* If path is NULL, imply AT_EMPTY_PATH. – But if it's "", don't — for safety reasons. */
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flags |= AT_EMPTY_PATH;
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if (size == SIZE_MAX)
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size = strlen(value);
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if (isempty(path)) {
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if (!FLAGS_SET(flags, AT_EMPTY_PATH))
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return -EINVAL;
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if (fd == AT_FDCWD) /* Both unspecified? Then operate on current working directory */
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path = ".";
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else {
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r = fd_is_opath(fd);
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if (r < 0)
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return r;
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by_procfs = r;
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path = NULL;
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}
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} else if (fd != AT_FDCWD) {
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/* If both have been specified, then we go via O_PATH */
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opened_fd = openat(fd, path, O_PATH|O_CLOEXEC|(FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? 0 : O_NOFOLLOW));
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if (opened_fd < 0)
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return -errno;
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fd = opened_fd;
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path = NULL;
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by_procfs = true; /* fsetxattr() is not going to work, go via /proc/ link right-away */
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}
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if (path)
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r = FLAGS_SET(flags, AT_SYMLINK_FOLLOW) ? setxattr(path, name, value, size, 0)
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: lsetxattr(path, name, value, size, 0);
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else
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r = by_procfs ? setxattr(FORMAT_PROC_FD_PATH(fd), name, value, size, 0)
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: fsetxattr(fd, name, value, size, 0);
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if (r < 0)
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return -errno;
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return 0;
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}
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