Improve compile-time overrun checking.

git-svn-id: svn://vcs.exim.org/pcre/code/trunk@505 2f5784b3-3f2a-0410-8824-cb99058d5e15

2 files changed, 12 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index 0f19c4c..6097440 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -57,6 +57,11 @@ Version 8.02 01-Mar-2010
     second branch in the above example - was incorrectly given the compile-
     time error "recursive call could loop indefinitely" because pcre_compile()
     was not correctly checking the subroutine for matching a non-empty string. 
+    
+14. The checks for overrunning compiling workspace could trigger after an
+    overrun had occurred. This is a "should never occur" error, but it can be 
+    triggered by pathological patterns such as hundreds of nested parentheses.
+    The checks now trigger 100 bytes before the end of the workspace. 
 
 
 Version 8.01 19-Jan-2010
diff --git a/pcre_compile.c b/pcre_compile.c
index 1a62ccb..090a613 100644
--- a/pcre_compile.c
+++ b/pcre_compile.c
@@ -92,6 +92,11 @@ is 4 there is plenty of room. */
 
 #define COMPILE_WORK_SIZE (4096)
 
+/* The overrun tests check for a slightly smaller size so that they detect the 
+overrun before it actually does run off the end of the data block. */
+
+#define WORK_SIZE_CHECK (COMPILE_WORK_SIZE - 100)
+
 
 /* Table for handling escaped characters in the range '0'-'z'. Positive returns
 are simple data values; negative values are for special things like \d and so
@@ -2760,7 +2765,7 @@ for (;; ptr++)
 #ifdef PCRE_DEBUG
     if (code > cd->hwm) cd->hwm = code;                 /* High water info */
 #endif
-    if (code > cd->start_workspace + COMPILE_WORK_SIZE) /* Check for overrun */
+    if (code > cd->start_workspace + WORK_SIZE_CHECK)   /* Check for overrun */
       {
       *errorcodeptr = ERR52;
       goto FAILED;
@@ -2809,7 +2814,7 @@ for (;; ptr++)
   /* In the real compile phase, just check the workspace used by the forward
   reference list. */
 
-  else if (cd->hwm > cd->start_workspace + COMPILE_WORK_SIZE)
+  else if (cd->hwm > cd->start_workspace + WORK_SIZE_CHECK)
     {
     *errorcodeptr = ERR52;
     goto FAILED;