[Pcre-svn] [1034] code/trunk: Fix heap limit checking overfl…

Revision: 1034

          http://www.exim.org/viewvc/pcre2?view=rev&revision=1034
Author:   ph10
Date:     2018-10-22 17:47:55 +0100 (Mon, 22 Oct 2018)
Log Message:
-----------
Fix heap limit checking overflow bug in pcre2_dfa_match().

Modified Paths:
--------------
    code/trunk/ChangeLog
    code/trunk/src/pcre2_dfa_match.c

Modified: code/trunk/ChangeLog
===================================================================
--- code/trunk/ChangeLog    2018-10-21 15:06:43 UTC (rev 1033)
+++ code/trunk/ChangeLog    2018-10-22 16:47:55 UTC (rev 1034)
@@ -48,7 +48,11 @@
 recorded. Example: /(?&xxx)*ABC(?<xxx>XYZ)/ would (incorrectly) expect 'A' to 
 be the first character of a match. 

+12. The heap limit checking code in pcre2_dfa_match() could suffer from
+overflow if the heap limit was set very large. This could cause incorrect "heap
+limit exceeded" errors.

+
Version 10.32 10-September-2018
-------------------------------

Modified: code/trunk/src/pcre2_dfa_match.c
===================================================================
--- code/trunk/src/pcre2_dfa_match.c    2018-10-21 15:06:43 UTC (rev 1033)
+++ code/trunk/src/pcre2_dfa_match.c    2018-10-22 16:47:55 UTC (rev 1034)
@@ -319,8 +319,8 @@

typedef struct RWS_anchor {
struct RWS_anchor *next;
- unsigned int size; /* Number of ints */
- unsigned int free; /* Number of ints */
+ uint32_t size; /* Number of ints */
+ uint32_t free; /* Number of ints */
} RWS_anchor;

#define RWS_ANCHOR_SIZE (sizeof(RWS_anchor)/sizeof(int))
@@ -416,20 +416,24 @@
new = rws->next;
}

-/* All sizes are in units of sizeof(int), except for mb->heaplimit, which is in
-kibibytes. */
+/* Sizes in the RWS_anchor blocks are in units of sizeof(int), but
+mb->heap_limit and mb->heap_used are in kibibytes. Play carefully, to avoid
+overflow. */

 else
   {
-  unsigned int newsize = rws->size * 2;
-  unsigned int heapleft = (unsigned int)
-    (((1024/sizeof(int))*mb->heap_limit - mb->heap_used));
-  if (newsize > heapleft) newsize = heapleft;
+  uint32_t newsize = (rws->size >= UINT32_MAX/2)? UINT32_MAX/2 : rws->size * 2;
+  uint32_t newsizeK = newsize/(1024/sizeof(int));
+
+  if (newsizeK + mb->heap_used > mb->heap_limit)
+    newsizeK = mb->heap_limit - mb->heap_used;
+  newsize = newsizeK*(1024/sizeof(int));
+
   if (newsize < RWS_RSIZE + ovecsize + RWS_ANCHOR_SIZE)
     return PCRE2_ERROR_HEAPLIMIT;
   new = mb->memctl.malloc(newsize*sizeof(int), mb->memctl.memory_data);
   if (new == NULL) return PCRE2_ERROR_NOMEMORY;
-  mb->heap_used += newsize;
+  mb->heap_used += newsizeK;
   new->next = NULL;
   new->size = newsize;
   rws->next = new;
@@ -3270,11 +3274,11 @@
 /* A length equal to PCRE2_ZERO_TERMINATED implies a zero-terminated
 subject string. */

-if (length == PCRE2_ZERO_TERMINATED)
+if (length == PCRE2_ZERO_TERMINATED)
{
length = PRIV(strlen)(subject);
was_zero_terminated = 1;
- }
+ }

/* Plausibility checks */

@@ -3532,10 +3536,10 @@

 if ((match_data->flags & PCRE2_MD_COPIED_SUBJECT) != 0)
   {
-  match_data->memctl.free((void *)match_data->subject, 
+  match_data->memctl.free((void *)match_data->subject,
     match_data->memctl.memory_data);
   match_data->flags &= ~PCRE2_MD_COPIED_SUBJECT;
-  }    
+  }

/* Fill in fields that are always returned in the match data. */

@@ -3845,9 +3849,9 @@
       memcpy((void *)match_data->subject, subject, length);
       match_data->flags |= PCRE2_MD_COPIED_SUBJECT;
       }
-    else 
-      { 
-      if (rc >= 0 || rc == PCRE2_ERROR_PARTIAL) match_data->subject = subject;   
+    else
+      {
+      if (rc >= 0 || rc == PCRE2_ERROR_PARTIAL) match_data->subject = subject;
       }
     goto EXIT;
     }