Merge pull request #24939 from msizanoen1/journal-realtime-enforce-consistency

journal: enforce strict consistency for realtime timestamps on write

src/journal/journald-server.c

@@ -839,6 +839,10 @@ static bool shall_try_append_again(JournalFile *f, int r) {
                 log_ratelimit_warning(JOURNAL_LOG_RATELIMIT, "%s: Journal file is from the future, rotating.", f->path);
                 return true;
 
+        case -EREMCHG:         /* Time jumped backwards relative to last journal entry */
+                log_ratelimit_warning(JOURNAL_LOG_RATELIMIT, "%s: Time jumped backwards relative to last journal entry, rotating.", f->path);
+                return true;
+
         case -EAFNOSUPPORT:
                 log_ratelimit_warning(JOURNAL_LOG_RATELIMIT,
                                       "%s: underlying file system does not support memory mapping or another required file system feature.",

src/journal/managed-journal-file.c

@@ -524,7 +524,8 @@ int managed_journal_file_open_reliably(
                     -ESHUTDOWN,         /* Already archived */
                     -EIO,               /* IO error, including SIGBUS on mmap */
                     -EIDRM,             /* File has been deleted */
-                    -ETXTBSY))          /* File is from the future */
+                    -ETXTBSY,           /* File is from the future */
+                    -EREMCHG))          /* Clock rolled back */
                 return r;
 
         if ((open_flags & O_ACCMODE) == O_RDONLY)

src/journal/test-journal-flush.c

@@ -58,7 +58,8 @@ static void test_journal_flush(int argc, char *argv[]) {
                 assert_se(r >= 0 ||
                           IN_SET(r, -EBADMSG,         /* corrupted file */
                                     -EPROTONOSUPPORT, /* unsupported compression */
-                                    -EIO));           /* file rotated */
+                                    -EIO,             /* file rotated */
+                                    -EREMCHG));       /* clock rollback */
 
                 if (++n >= 10000)
                         break;

src/libsystemd/sd-journal/journal-file.c

@@ -2092,6 +2092,12 @@ static int journal_file_append_entry_internal(
         assert(ts);
         assert(items || n_items == 0);
 
+        if (ts->realtime < le64toh(f->header->tail_entry_realtime))
+                return log_debug_errno(SYNTHETIC_ERRNO(EREMCHG),
+                                       "Realtime timestamp %" PRIu64 " smaller than previous realtime "
+                                       "timestamp %" PRIu64 ", refusing entry.",
+                                       ts->realtime, le64toh(f->header->tail_entry_realtime));
+
         osize = offsetof(Object, entry.items) + (n_items * journal_file_entry_item_size(f));
 
         r = journal_file_append_object(f, OBJECT_ENTRY, osize, &o, &np);