syslog: Fix large messages (BZ#29536)

The a583b6add407c17cd change did not handle large messages that
would require a heap allocation correctly, where the message itself
is not take in consideration.

This patch fixes it and extend the tst-syslog to check for large
messages as well.

Checked on x86_64-linux-gnu.

Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>

2 files changed, 142 insertions, 28 deletions

diff --git a/misc/syslog.c b/misc/syslog.c
index 554089bfc4..b88f66c835 100644
--- a/misc/syslog.c
+++ b/misc/syslog.c
@@ -193,28 +193,32 @@ __vsyslog_internal (int pri, const char *fmt, va_list ap,
       int vl = __vsnprintf_internal (bufs + l, sizeof bufs - l, fmt, apc,
                                      mode_flags);
       if (0 <= vl && vl < sizeof bufs - l)
-        {
-          buf = bufs;
-          bufsize = l + vl;
-        }
+        buf = bufs;
+      bufsize = l + vl;
 
       va_end (apc);
     }
 
   if (buf == NULL)
     {
-      buf = malloc (l * sizeof (char));
+      buf = malloc ((bufsize + 1) * sizeof (char));
       if (buf != NULL)
 	{
 	  /* Tell the cancellation handler to free this buffer.  */
 	  clarg.buf = buf;
 
 	  if (has_ts)
-	    __snprintf (bufs, sizeof bufs,
+	    __snprintf (buf, l + 1,
 			SYSLOG_HEADER (pri, timestamp, &msgoff, pid));
 	  else
-	    __snprintf (bufs, sizeof bufs,
+	    __snprintf (buf, l + 1,
 			SYSLOG_HEADER_WITHOUT_TS (pri, &msgoff));
+
+	  va_list apc;
+	  va_copy (apc, ap);
+	  __vsnprintf_internal (buf + l, bufsize - l + 1, fmt, apc,
+				mode_flags);
+	  va_end (apc);
 	}
       else
         {
diff --git a/misc/tst-syslog.c b/misc/tst-syslog.c
index e550d15796..1d332ece53 100644
--- a/misc/tst-syslog.c
+++ b/misc/tst-syslog.c
@@ -68,21 +68,19 @@ static const int priorities[] =
     LOG_DEBUG
   };
 
-enum
-  {
-    ident_length = 64,
-    msg_length = 64
-  };
+#define IDENT_LENGTH 64
+#define MSG_LENGTH   1024
 
 #define SYSLOG_MSG_BASE "syslog_message"
 #define OPENLOG_IDENT   "openlog_ident"
+static char large_message[MSG_LENGTH];
 
 struct msg_t
   {
     int priority;
     int facility;
-    char ident[ident_length];
-    char msg[msg_length];
+    char ident[IDENT_LENGTH];
+    char msg[MSG_LENGTH];
     pid_t pid;
   };
 
@@ -148,6 +146,37 @@ check_syslog_message (const struct msg_t *msg, int msgnum, int options,
 }
 
 static void
+send_syslog_large (int options)
+{
+  int facility = LOG_USER;
+  int priority = LOG_INFO;
+
+  syslog (facility | priority, "%s %d %d", large_message, facility,
+	  priority);
+}
+
+static void
+send_vsyslog_large (int options)
+{
+  int facility = LOG_USER;
+  int priority = LOG_INFO;
+
+  call_vsyslog (facility | priority, "%s %d %d", large_message, facility,
+		priority);
+}
+
+static bool
+check_syslog_message_large (const struct msg_t *msg, int msgnum, int options,
+			    pid_t pid)
+{
+  TEST_COMPARE (msg->facility, LOG_USER);
+  TEST_COMPARE (msg->priority, LOG_INFO);
+  TEST_COMPARE_STRING (msg->msg, large_message);
+
+  return false;
+}
+
+static void
 send_openlog (int options)
 {
   /* Define a non-default IDENT and a not default facility.  */
@@ -179,6 +208,17 @@ send_openlog (int options)
   closelog ();
 }
 
+static void
+send_openlog_large (int options)
+{
+  /* Define a non-default IDENT and a not default facility.  */
+  openlog (OPENLOG_IDENT, options, LOG_LOCAL0);
+
+  syslog (LOG_INFO, "%s %d %d", large_message, LOG_LOCAL0, LOG_INFO);
+
+  closelog ();
+}
+
 static bool
 check_openlog_message (const struct msg_t *msg, int msgnum,
                        int options, pid_t pid)
@@ -189,7 +229,7 @@ check_openlog_message (const struct msg_t *msg, int msgnum,
   int expected_priority = priorities[msgnum % array_length (priorities)];
   TEST_COMPARE (msg->priority, expected_priority);
 
-  char expected_ident[ident_length];
+  char expected_ident[IDENT_LENGTH];
   snprintf (expected_ident, sizeof (expected_ident), "%s%s%.0d%s:",
             OPENLOG_IDENT,
             options & LOG_PID ? "[" : "",
@@ -211,15 +251,38 @@ check_openlog_message (const struct msg_t *msg, int msgnum,
   return true;
 }
 
+static bool
+check_openlog_message_large (const struct msg_t *msg, int msgnum,
+			     int options, pid_t pid)
+{
+  char expected_ident[IDENT_LENGTH];
+  snprintf (expected_ident, sizeof (expected_ident), "%s%s%.0d%s:",
+            OPENLOG_IDENT,
+            options & LOG_PID ? "[" : "",
+            options & LOG_PID ? pid : 0,
+            options & LOG_PID ? "]" : "");
+
+  TEST_COMPARE_STRING (msg->ident, expected_ident);
+  TEST_COMPARE_STRING (msg->msg, large_message);
+  TEST_COMPARE (msg->priority, LOG_INFO);
+  TEST_COMPARE (msg->facility, LOG_LOCAL0);
+
+  return false;
+}
+
 static struct msg_t
 parse_syslog_msg (const char *msg)
 {
   struct msg_t r = { .pid = -1 };
   int number;
 
+#define STRINPUT(size)  XSTRINPUT(size)
+#define XSTRINPUT(size) "%" # size "s"
+
   /* The message in the form:
-     <179>Apr  8 14:51:19 tst-syslog: syslog message 176 3  */
-  int n = sscanf (msg, "<%3d>%*s %*d %*d:%*d:%*d %32s %64s %*d %*d",
+     <179>Apr  8 14:51:19  tst-syslog: message 176 3  */
+  int n = sscanf (msg, "<%3d>%*s %*d %*d:%*d:%*d " STRINPUT(IDENT_LENGTH)
+		       " " STRINPUT(MSG_LENGTH) " %*d %*d",
                   &number, r.ident, r.msg);
   TEST_COMPARE (n, 3);
 
@@ -246,7 +309,7 @@ parse_syslog_console (const char *msg)
 
   /* The message in the form:
      openlog_ident: syslog_message 128 0  */
-  int n = sscanf (msg, "%32s %64s %d %d",
+  int n = sscanf (msg, STRINPUT(IDENT_LENGTH) " " STRINPUT(MSG_LENGTH) " %d %d",
       r.ident, r.msg, &facility, &priority);
   TEST_COMPARE (n, 4);
 
@@ -281,7 +344,7 @@ check_syslog_udp (void (*syslog_send)(int), int options,
   int msgnum = 0;
   while (1)
     {
-      char buf[512];
+      char buf[2048];
       size_t l = xrecvfrom (server_udp, buf, sizeof (buf), 0,
                             (struct sockaddr *) &addr, &addrlen);
       buf[l] = '\0';
@@ -325,7 +388,7 @@ check_syslog_tcp (void (*syslog_send)(int), int options,
 
   int client_tcp = xaccept (server_tcp, NULL, NULL);
 
-  char buf[512], *rb = buf;
+  char buf[2048], *rb = buf;
   size_t rbl = sizeof (buf);
   size_t prl = 0;  /* Track the size of the partial record.  */
   int msgnum = 0;
@@ -393,20 +456,34 @@ check_syslog_console_read (FILE *fp)
 }
 
 static void
-check_syslog_console (void)
+check_syslog_console_read_large (FILE *fp)
+{
+  char buf[2048];
+  TEST_VERIFY (fgets (buf, sizeof (buf), fp) != NULL);
+  struct msg_t msg = parse_syslog_console (buf);
+
+  TEST_COMPARE_STRING (msg.ident, OPENLOG_IDENT ":");
+  TEST_COMPARE_STRING (msg.msg, large_message);
+  TEST_COMPARE (msg.priority, LOG_INFO);
+  TEST_COMPARE (msg.facility, LOG_LOCAL0);
+}
+
+static void
+check_syslog_console (void (*syslog_send)(int),
+		      void (*syslog_check)(FILE *fp))
 {
   xmkfifo (_PATH_CONSOLE, 0666);
 
   pid_t sender_pid = xfork ();
   if (sender_pid == 0)
     {
-      send_openlog (LOG_CONS);
+      syslog_send (LOG_CONS);
       _exit (0);
     }
 
   {
     FILE *fp = xfopen (_PATH_CONSOLE, "r+");
-    check_syslog_console_read (fp);
+    syslog_check (fp);
     xfclose (fp);
   }
 
@@ -425,16 +502,28 @@ send_openlog_callback (void *clousure)
 }
 
 static void
-check_syslog_perror (void)
+send_openlog_callback_large (void *clousure)
+{
+  int options = *(int *) clousure;
+  send_openlog_large (options);
+}
+
+static void
+check_syslog_perror (bool large)
 {
   struct support_capture_subprocess result;
-  result = support_capture_subprocess (send_openlog_callback,
+  result = support_capture_subprocess (large
+				       ? send_openlog_callback_large
+				       : send_openlog_callback,
                                        &(int){LOG_PERROR});
 
   FILE *mfp = fmemopen (result.err.buffer, result.err.length, "r");
   if (mfp == NULL)
     FAIL_EXIT1 ("fmemopen: %m");
-  check_syslog_console_read (mfp);
+  if (large)
+    check_syslog_console_read_large (mfp);
+  else
+    check_syslog_console_read (mfp);
   xfclose (mfp);
 
   support_capture_subprocess_check (&result, "tst-openlog-child", 0,
@@ -462,10 +551,31 @@ do_test (void)
   check_syslog_tcp (send_openlog, LOG_PID, check_openlog_message);
 
   /* Check the LOG_CONS option.  */
-  check_syslog_console ();
+  check_syslog_console (send_openlog, check_syslog_console_read);
 
   /* Check the LOG_PERROR option.  */
-  check_syslog_perror ();
+  check_syslog_perror (false);
+
+  /* Similar tests as before, but with a large message to trigger the
+     syslog path that uses dynamically allocated memory.  */
+  memset (large_message, 'a', sizeof large_message - 1);
+  large_message[sizeof large_message - 1] = '\0';
+
+  check_syslog_udp (send_syslog_large, 0, check_syslog_message_large);
+  check_syslog_tcp (send_syslog_large, 0, check_syslog_message_large);
+
+  check_syslog_udp (send_vsyslog_large, 0, check_syslog_message_large);
+  check_syslog_tcp (send_vsyslog_large, 0, check_syslog_message_large);
+
+  check_syslog_udp (send_openlog_large, 0, check_openlog_message_large);
+  check_syslog_tcp (send_openlog_large, 0, check_openlog_message_large);
+
+  check_syslog_udp (send_openlog_large, LOG_PID, check_openlog_message_large);
+  check_syslog_tcp (send_openlog_large, LOG_PID, check_openlog_message_large);
+
+  check_syslog_console (send_openlog_large, check_syslog_console_read_large);
+
+  check_syslog_perror (true);
 
   return 0;
 }