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authorIvan Shapovalov <intelfx@intelfx.name>2016-09-13 03:04:35 +0300
committerIvan Shapovalov <intelfx@intelfx.name>2016-09-15 06:36:42 +0300
commitfb8b0869a7bc30e23be175cf978df23192d59118 (patch)
tree9524b559719dd9a03e100739f68123a4f4dcea8b
parent3a730176b36bc1191c54b149a8147bbf6ec8e482 (diff)
update-done, condition: write the timestamp to the file as well and use it to prevent false-positives
This fixes https://bugs.freedesktop.org/show_bug.cgi?id=90192 and #4130 for real. Also, remove timestamp check in update-done.c altogether since the whole operation is idempotent.
-rw-r--r--src/shared/condition.c42
-rw-r--r--src/update-done/update-done.c76
2 files changed, 73 insertions, 45 deletions
diff --git a/src/shared/condition.c b/src/shared/condition.c
index 6bb42c0692..f13fa6a9fd 100644
--- a/src/shared/condition.c
+++ b/src/shared/condition.c
@@ -37,6 +37,7 @@
#include "condition.h"
#include "extract-word.h"
#include "fd-util.h"
+#include "fileio.h"
#include "glob-util.h"
#include "hostname-util.h"
#include "ima-util.h"
@@ -309,8 +310,45 @@ static int condition_test_needs_update(Condition *c) {
if (lstat("/usr/", &usr) < 0)
return true;
- return usr.st_mtim.tv_sec > other.st_mtim.tv_sec ||
- (usr.st_mtim.tv_sec == other.st_mtim.tv_sec && usr.st_mtim.tv_nsec > other.st_mtim.tv_nsec);
+ /*
+ * First, compare seconds as they are always accurate...
+ */
+ if (usr.st_mtim.tv_sec != other.st_mtim.tv_sec)
+ return usr.st_mtim.tv_sec > other.st_mtim.tv_sec;
+
+ /*
+ * ...then compare nanoseconds.
+ *
+ * A false positive is only possible when /usr's nanoseconds > 0
+ * (otherwise /usr cannot be strictly newer than the target file)
+ * AND the target file's nanoseconds == 0
+ * (otherwise the filesystem supports nsec timestamps, see stat(2)).
+ */
+ if (usr.st_mtim.tv_nsec > 0 && other.st_mtim.tv_nsec == 0) {
+ _cleanup_free_ char *timestamp_str = NULL;
+ uint64_t timestamp;
+ int r;
+
+ r = parse_env_file(p, NULL, "TimestampNSec", &timestamp_str, NULL);
+ if (r < 0) {
+ log_error_errno(-r, "Failed to parse timestamp file '%s', using mtime: %m", p);
+ return true;
+ } else if (r == 0) {
+ log_debug("No data in timestamp file '%s', using mtime", p);
+ return true;
+ }
+
+ r = safe_atou64(timestamp_str, &timestamp);
+ if (r < 0) {
+ log_error_errno(-r, "Failed to parse timestamp value '%s' in file '%s', using mtime: %m",
+ timestamp_str, p);
+ return true;
+ }
+
+ other.st_mtim.tv_nsec = timestamp % NSEC_PER_SEC;
+ }
+
+ return usr.st_mtim.tv_nsec > other.st_mtim.tv_nsec;
}
static int condition_test_first_boot(Condition *c) {
diff --git a/src/update-done/update-done.c b/src/update-done/update-done.c
index da306a4444..5cc5abfddf 100644
--- a/src/update-done/update-done.c
+++ b/src/update-done/update-done.c
@@ -23,67 +23,57 @@
#include "util.h"
#define MESSAGE \
- "This file was created by systemd-update-done. Its only \n" \
- "purpose is to hold a timestamp of the time this directory\n" \
- "was updated. See systemd-update-done.service(8).\n"
+ "# This file was created by systemd-update-done. Its only \n" \
+ "# purpose is to hold a timestamp of the time this directory\n" \
+ "# was updated. See systemd-update-done.service(8).\n"
static int apply_timestamp(const char *path, struct timespec *ts) {
struct timespec twice[2] = {
*ts,
*ts
};
- struct stat st;
+ int fd = -1;
+ _cleanup_fclose_ FILE *f = NULL;
+ int r;
assert(path);
assert(ts);
- if (stat(path, &st) >= 0) {
- /* Is the timestamp file already newer than the OS? If
- * so, there's nothing to do. We ignore the nanosecond
- * component of the timestamp, since some file systems
- * do not support any better accuracy than 1s and we
- * have no way to identify the accuracy
- * available. Most notably ext4 on small disks (where
- * 128 byte inodes are used) does not support better
- * accuracy than 1s. */
- if (st.st_mtim.tv_sec > ts->tv_sec)
- return 0;
-
- /* It is older? Then let's update it */
- if (utimensat(AT_FDCWD, path, twice, AT_SYMLINK_NOFOLLOW) < 0) {
-
- if (errno == EROFS)
- return log_debug("Can't update timestamp file %s, file system is read-only.", path);
+ /*
+ * We store the timestamp both as mtime of the file and in the file itself,
+ * to support filesystems which cannot store nanosecond-precision timestamps.
+ * Hence, don't bother updating the file, let's just rewrite it.
+ */
- return log_error_errno(errno, "Failed to update timestamp on %s: %m", path);
- }
+ r = mac_selinux_create_file_prepare(path, S_IFREG);
+ if (r < 0)
+ return log_error_errno(r, "Failed to set SELinux context for %s: %m", path);
- } else if (errno == ENOENT) {
- _cleanup_close_ int fd = -1;
- int r;
+ fd = open(path, O_CREAT|O_WRONLY|O_TRUNC|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0644);
+ mac_selinux_create_file_clear();
- /* The timestamp file doesn't exist yet? Then let's create it. */
+ if (fd < 0) {
+ if (errno == EROFS)
+ return log_debug("Can't create timestamp file %s, file system is read-only.", path);
- r = mac_selinux_create_file_prepare(path, S_IFREG);
- if (r < 0)
- return log_error_errno(r, "Failed to set SELinux context for %s: %m", path);
-
- fd = open(path, O_CREAT|O_EXCL|O_WRONLY|O_TRUNC|O_CLOEXEC|O_NOCTTY|O_NOFOLLOW, 0644);
- mac_selinux_create_file_clear();
+ return log_error_errno(errno, "Failed to create/open timestamp file %s: %m", path);
+ }
- if (fd < 0) {
- if (errno == EROFS)
- return log_debug("Can't create timestamp file %s, file system is read-only.", path);
+ f = fdopen(fd, "w");
+ if (!f) {
+ safe_close(fd);
+ return log_error_errno(errno, "Failed to fdopen() timestamp file %s: %m", path);
+ }
- return log_error_errno(errno, "Failed to create timestamp file %s: %m", path);
- }
+ (void) fprintf(f,
+ "%s"
+ "TimestampNSec=" NSEC_FMT "\n",
+ MESSAGE, timespec_load_nsec(ts));
- (void) loop_write(fd, MESSAGE, strlen(MESSAGE), false);
+ fflush(f);
- if (futimens(fd, twice) < 0)
- return log_error_errno(errno, "Failed to update timestamp on %s: %m", path);
- } else
- log_error_errno(errno, "Failed to stat() timestamp file %s: %m", path);
+ if (futimens(fd, twice) < 0)
+ return log_error_errno(errno, "Failed to update timestamp on %s: %m", path);
return 0;
}