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* mandoc: Do not abuse assert(3) to react to absurd input; the purpose of
@ 2020-09-09 13:45 schwarze
  0 siblings, 0 replies; only message in thread
From: schwarze @ 2020-09-09 13:45 UTC (permalink / raw)
  To: source

Log Message:
-----------
Do not abuse assert(3) to react to absurd input; the purpose of assert(3) 
only is to catch internal inconsistencies in the program itself.
Issue found in an afl run performed by Jan Schreiber <jes at posteo dot de>.

Instead, just cut down unreasonably wide spacing requested by the document 
to a narrower width.

Modified Files:
--------------
    mandoc:
        term_ascii.c

Revision Data
-------------
Index: term_ascii.c
===================================================================
RCS file: /home/cvs/mandoc/mandoc/term_ascii.c,v
retrieving revision 1.65
retrieving revision 1.66
diff -Lterm_ascii.c -Lterm_ascii.c -u -p -r1.65 -r1.66
--- term_ascii.c
+++ term_ascii.c
@@ -245,7 +245,14 @@ ascii_advance(struct termp *p, size_t le
 {
 	size_t		i;
 
-	assert(len < UINT16_MAX);
+	/*
+	 * XXX We used to have "assert(len < UINT16_MAX)" here.
+	 * that is not quite right because the input document
+	 * can trigger that by merely providing large input.
+	 * For now, simply truncate.
+	 */
+	if (len > 256)
+		len = 256;
 	for (i = 0; i < len; i++)
 		putchar(' ');
 }
@@ -383,7 +390,14 @@ locale_advance(struct termp *p, size_t l
 {
 	size_t		i;
 
-	assert(len < UINT16_MAX);
+	/*
+	 * XXX We used to have "assert(len < UINT16_MAX)" here.
+	 * that is not quite right because the input document
+	 * can trigger that by merely providing large input.
+	 * For now, simply truncate.
+	 */
+	if (len > 256)
+		len = 256;
 	for (i = 0; i < len; i++)
 		putwchar(L' ');
 }
--
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2020-09-09 13:45 mandoc: Do not abuse assert(3) to react to absurd input; the purpose of schwarze

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