BUG/MINOR: logs/threads: properly split the log area upon startup

If logs were emitted before creating the threads, then the dataptr pointer
keeps a copy of the end of the log header. Then after the threads are
created, the headers are reallocated for each thread. However the end
pointer was not reset until the end of the first second, which may result
in logs emitted by multiple threads during the first second to be mangled,
or possibly in some cases to use a memory area that was reused for something
else. The fix simply consists in reinitializing the end pointers immediately
when the threads are created.

This fix must be backported to 1.9 and 1.8.

diff --git a/src/log.c b/src/log.c
index 866ff23f713226f86aa8f66146b097637a122731..a075b85e46a34df141dceed66f6583667bd370af 100644 (file)
--- a/src/log.c
+++ b/src/log.c
@@ -232,11 +232,13 @@ unsigned int dropped_logs = 0;
  * update_log_hdr().
  */
 THREAD_LOCAL char *logheader = NULL;
+THREAD_LOCAL char *logheader_end = NULL;
 
 /* This is a global syslog header for messages in RFC5424 format. It is
  * updated by update_log_hdr_rfc5424().
  */
 THREAD_LOCAL char *logheader_rfc5424 = NULL;
+THREAD_LOCAL char *logheader_rfc5424_end = NULL;
 
 /* This is a global syslog message buffer, common to all outgoing
  * messages. It contains only the data part.
@@ -1363,11 +1365,10 @@ char *lf_port(char *dst, const struct sockaddr *sockaddr, size_t size, const str
 static char *update_log_hdr(const time_t time)
 {
        static THREAD_LOCAL long tvsec;
-       static THREAD_LOCAL char *dataptr = NULL; /* backup of last end of header, NULL first time */
        static THREAD_LOCAL struct buffer host = { };
        static THREAD_LOCAL int sep = 0;
 
-       if (unlikely(time != tvsec || dataptr == NULL)) {
+       if (unlikely(time != tvsec || logheader_end == NULL)) {
                /* this string is rebuild only once a second */
                struct tm tm;
                int hdr_len;
@@ -1393,12 +1394,12 @@ static char *update_log_hdr(const time_t time)
                if (hdr_len < 0 || hdr_len > global.max_syslog_len)
                        hdr_len = global.max_syslog_len;
 
-               dataptr = logheader + hdr_len;
+               logheader_end = logheader + hdr_len;
        }
 
-       dataptr[0] = 0; // ensure we get rid of any previous attempt
+       logheader_end[0] = 0; // ensure we get rid of any previous attempt
 
-       return dataptr;
+       return logheader_end;
 }
 
 /* Re-generate time-based part of the syslog header in RFC5424 format at
@@ -1408,10 +1409,9 @@ static char *update_log_hdr(const time_t time)
 static char *update_log_hdr_rfc5424(const time_t time)
 {
        static THREAD_LOCAL long tvsec;
-       static THREAD_LOCAL char *dataptr = NULL; /* backup of last end of header, NULL first time */
        const char *gmt_offset;
 
-       if (unlikely(time != tvsec || dataptr == NULL)) {
+       if (unlikely(time != tvsec || logheader_rfc5424_end == NULL)) {
                /* this string is rebuild only once a second */
                struct tm tm;
                int hdr_len;
@@ -1433,12 +1433,12 @@ static char *update_log_hdr_rfc5424(const time_t time)
                if (hdr_len < 0 || hdr_len > global.max_syslog_len)
                        hdr_len = global.max_syslog_len;
 
-               dataptr = logheader_rfc5424 + hdr_len;
+               logheader_rfc5424_end = logheader_rfc5424 + hdr_len;
        }
 
-       dataptr[0] = 0; // ensure we get rid of any previous attempt
+       logheader_rfc5424_end[0] = 0; // ensure we get rid of any previous attempt
 
-       return dataptr;
+       return logheader_rfc5424_end;
 }
 
 /*
@@ -1878,7 +1878,9 @@ static void deinit_log_buffers_per_thread()
 int init_log_buffers()
 {
        logheader = my_realloc2(logheader, global.max_syslog_len + 1);
+       logheader_end = NULL;
        logheader_rfc5424 = my_realloc2(logheader_rfc5424, global.max_syslog_len + 1);
+       logheader_rfc5424_end = NULL;
        logline = my_realloc2(logline, global.max_syslog_len + 1);
        logline_rfc5424 = my_realloc2(logline_rfc5424, global.max_syslog_len + 1);
        if (!logheader || !logline_rfc5424 || !logline || !logline_rfc5424)