syslog: Fix heap buffer overflow in __vsyslog_internal (CVE-2023-6779)

[thirdparty/glibc.git] / misc / syslog.c

diff --git a/misc/syslog.c b/misc/syslog.c
index 814d224a1e9cfbd31a31a24bdf789f6a2c7cab7e..53440e47ad459085ea196efcddf8b9a7af3dcba0 100644 (file)
--- a/misc/syslog.c
+++ b/misc/syslog.c
@@ -185,11 +185,13 @@ __vsyslog_internal (int pri, const char *fmt, va_list ap,
   else
     l = __snprintf (bufs, sizeof bufs,
                    SYSLOG_HEADER_WITHOUT_TS (pri, &msgoff));
+  if (l < 0)
+    goto out;
 
   char *pos;
   size_t len;
 
-  if (0 <= l && l < sizeof bufs)
+  if (l < sizeof bufs)
     {
       /* At this point, there is still a chance that we can print the
          remaining part of the log into bufs and use that.  */
@@ -215,12 +217,15 @@ __vsyslog_internal (int pri, const char *fmt, va_list ap,
     __set_errno (saved_errno);
 
     vl = __vsnprintf_internal (pos, len, fmt, apc, mode_flags);
+    va_end (apc);
+
+    if (vl < 0)
+      goto out;
 
-    if (!(0 <= vl && vl < len))
+    if (vl >= len)
       buf = NULL;
 
     bufsize = l + vl;
-    va_end (apc);
   }
 
   if (buf == NULL)
@@ -231,25 +236,37 @@ __vsyslog_internal (int pri, const char *fmt, va_list ap,
          /* Tell the cancellation handler to free this buffer.  */
          clarg.buf = buf;
 
+         int cl;
          if (has_ts)
-           __snprintf (buf, l + 1,
-                       SYSLOG_HEADER (pri, timestamp, &msgoff, pid));
+           cl = __snprintf (buf, l + 1,
+                            SYSLOG_HEADER (pri, timestamp, &msgoff, pid));
          else
-           __snprintf (buf, l + 1,
-                       SYSLOG_HEADER_WITHOUT_TS (pri, &msgoff));
+           cl = __snprintf (buf, l + 1,
+                            SYSLOG_HEADER_WITHOUT_TS (pri, &msgoff));
+         if (cl != l)
+           goto out;
 
          va_list apc;
          va_copy (apc, ap);
-         __vsnprintf_internal (buf + l, bufsize - l + 1, fmt, apc,
-                               mode_flags);
+         cl = __vsnprintf_internal (buf + l, bufsize - l + 1, fmt, apc,
+                                    mode_flags);
          va_end (apc);
+
+         if (cl != vl)
+           goto out;
        }
       else
         {
+          int bl;
          /* Nothing much to do but emit an error message.  */
-          bufsize = __snprintf (bufs, sizeof bufs,
-                                "out of memory[%d]", __getpid ());
+          bl = __snprintf (bufs, sizeof bufs,
+                           "out of memory[%d]", __getpid ());
+          if (bl < 0 || bl >= sizeof bufs)
+            goto out;
+
+          bufsize = bl;
           buf = bufs;
+          msgoff = 0;
         }
     }