klogctl: fix a problem where we don't terminate read data with '\0'

 and then misinterpret it. Code shrink while at it.

function                                             old     new   delta
klogd_main                                           404     362     -42

1 files changed, 17 insertions, 20 deletions

diff --git a/sysklogd/klogd.c b/sysklogd/klogd.c
index 723ca8067..a0e0bf724 100644
--- a/sysklogd/klogd.c
+++ b/sysklogd/klogd.c
@@ -42,14 +42,14 @@ int klogd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int klogd_main(int argc UNUSED_PARAM, char **argv)
 {
         int i = 0;
-        char *start;
+        char *opt_c;
         int opt;
         int used = 0;
 
-        opt = getopt32(argv, "c:n", &start);
+        opt = getopt32(argv, "c:n", &opt_c);
         if (opt & OPT_LEVEL) {
                 /* Valid levels are between 1 and 8 */
-                i = xatou_range(start, 1, 8);
+                i = xatou_range(opt_c, 1, 8);
         }
         if (!(opt & OPT_FOREGROUND)) {
                 bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv);
@@ -57,10 +57,7 @@ int klogd_main(int argc UNUSED_PARAM, char **argv)
 
         openlog("kernel", 0, LOG_KERN);
 
-        bb_signals(0
-                + (1 << SIGINT)
-                + (1 << SIGTERM)
-                , klogd_signal);
+        bb_signals(BB_FATAL_SIGS, klogd_signal);
         signal(SIGHUP, SIG_IGN);
 
         /* "Open the log. Currently a NOP" */
@@ -73,15 +70,14 @@ int klogd_main(int argc UNUSED_PARAM, char **argv)
 
         syslog(LOG_NOTICE, "klogd started: %s", bb_banner);
 
-        /* Initially null terminate the buffer in case of a very long line */
-        log_buffer[KLOGD_LOGBUF_SIZE - 1] = '\0';
-
         while (1) {
                 int n;
                 int priority;
+                char *start;
 
                 /* "2 -- Read from the log." */
-                n = klogctl(2, log_buffer + used, KLOGD_LOGBUF_SIZE-1 - used);
+                start = log_buffer + used;
+                n = klogctl(2, start, KLOGD_LOGBUF_SIZE-1 - used);
                 if (n < 0) {
                         if (errno == EINTR)
                                 continue;
@@ -89,25 +85,25 @@ int klogd_main(int argc UNUSED_PARAM, char **argv)
                                         errno);
                         break;
                 }
+                start[n] = '\0';
 
                 /* klogctl buffer parsing modelled after code in dmesg.c */
-                start = &log_buffer[0];
-
                 /* Process each newline-terminated line in the buffer */
                 while (1) {
-                        char *newline = strchr(start, '\n');
+                        char *newline = strchrnul(start, '\n');
 
-                        if (!newline) {
+                        if (*newline == '\0') {
                                 /* This line is incomplete... */
                                 if (start != log_buffer) {
                                         /* move it to the front of the buffer */
-                                        strcpy(log_buffer, start);
+                                        overlapping_strcpy(log_buffer, start);
+                                        used = newline - start;
                                         /* don't log it yet */
-                                        used = strlen(log_buffer);
                                         break;
                                 }
-                                /* ...but buffer is full, so log it anyway */
+                                /* ...but if buffer is full, log it anyway */
                                 used = 0;
+                                newline = NULL;
                         } else {
                                 *newline++ = '\0';
                         }
@@ -121,12 +117,13 @@ int klogd_main(int argc UNUSED_PARAM, char **argv)
                                         priority = (*start - '0');
                                         start++;
                                 }
-                                if (*start == '>') {
+                                if (*start == '>')
                                         start++;
-                                }
                         }
+                        /* Log (only non-empty lines) */
                         if (*start)
                                 syslog(priority, "%s", start);
+
                         if (!newline)
                                 break;
                         start = newline;