- Fixed bug #54055 (buffer overrun with high values for precision ini

setting).
#This fix (for g/G/k/H modes) is done at a different level than that for the
#modes e/E/f/F, at a bit higher level and therefore with less coverage. I
#chose this because it addresses the problem where it is -- the calling function
#that passes a buffer too small to php_gcvt.

ext/standard/tests/strings/bug54055.phpt

@@ -0,0 +1,589 @@
+--TEST--
+Bug #54055: PHP crashes when executing strval when precision setting is very high
+--FILE--
+<?php
+for($i = 495; $i <= 1074; $i++) {
+  ini_set('precision', $i);
+  echo "$i: len=", strlen(strval(-1 * pow(2, -1074))), "\n";
+}
+--EXPECT--
+495: len=502
+496: len=503
+497: len=504
+498: len=505
+499: len=506
+500: len=507
+501: len=507
+502: len=507
+503: len=507
+504: len=507
+505: len=507
+506: len=507
+507: len=507
+508: len=507
+509: len=507
+510: len=507
+511: len=507
+512: len=507
+513: len=507
+514: len=507
+515: len=507
+516: len=507
+517: len=507
+518: len=507
+519: len=507
+520: len=507
+521: len=507
+522: len=507
+523: len=507
+524: len=507
+525: len=507
+526: len=507
+527: len=507
+528: len=507
+529: len=507
+530: len=507
+531: len=507
+532: len=507
+533: len=507
+534: len=507
+535: len=507
+536: len=507
+537: len=507
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+543: len=507
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+570: len=507
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+1073: len=507
+1074: len=507

main/snprintf.c

@@ -677,10 +677,6 @@ static int format_converter(register buffy * odp, const char *fmt, va_list ap) /
 
 				/*
 				 * Check if a precision was specified
-				 *
-				 * XXX: an unreasonable amount of precision may be specified
-				 * resulting in overflow of num_buf. Currently we
-				 * ignore this possibility.
 				 */
 				if (*fmt == '.') {
 					adjust_precision = YES;
@@ -694,6 +690,10 @@ static int format_converter(register buffy * odp, const char *fmt, va_list ap) /
 							precision = 0;
 					} else
 						precision = 0;
+					
+					if (precision > FORMAT_CONV_MAX_PRECISION) {
+						precision = FORMAT_CONV_MAX_PRECISION;
+					}
 				} else
 					adjust_precision = NO;
 			} else

main/snprintf.h

@@ -12,7 +12,7 @@
    | obtain it through the world-wide-web, please send a note to          |
    | license@php.net so we can mail you a copy immediately.               |
    +----------------------------------------------------------------------+
-   | Author: Stig Sæther Bakken <ssb@php.net>                             |
+   | Author: Stig Sæther Bakken <ssb@php.net>                             |
    |         Marcus Boerger <helly@php.net>                               |
    +----------------------------------------------------------------------+
 */
@@ -158,6 +158,17 @@ extern char * ap_php_conv_10(register wide_int num, register bool_int is_unsigne
 extern char * ap_php_conv_p2(register u_wide_int num, register int nbits,
 		 char format, char *buf_end, register int *len);
 
+/* The maximum precision that's allowed for float conversion. Does not include
+ * decimal separator, exponent, sign, terminator. Currently does not affect
+ * the modes e/f, only g/k/H, as those have a different limit enforced at
+ * another level (see NDIG in php_conv_fp()).
+ * Applies to the formatting functions of both spprintf.c and snprintf.c, which
+ * use equally sized buffers of MAX_BUF_SIZE = 512 to hold the result of the
+ * call to php_gcvt().
+ * This should be reasonably smaller than MAX_BUF_SIZE (I think MAX_BUF_SIZE - 9
+ * should be enough, but let's give some more space) */
+#define FORMAT_CONV_MAX_PRECISION 500
+
 #endif /* SNPRINTF_H */
 
 /*

main/spprintf.c

@@ -285,10 +285,6 @@ static void xbuf_format_converter(smart_str *xbuf, const char *fmt, va_list ap)
 
 				/*
 				 * Check if a precision was specified
-				 *
-				 * XXX: an unreasonable amount of precision may be specified
-				 * resulting in overflow of num_buf. Currently we
-				 * ignore this possibility.
 				 */
 				if (*fmt == '.') {
 					adjust_precision = YES;
@@ -302,6 +298,10 @@ static void xbuf_format_converter(smart_str *xbuf, const char *fmt, va_list ap)
 							precision = 0;
 					} else
 						precision = 0;
+					
+					if (precision > FORMAT_CONV_MAX_PRECISION) {
+						precision = FORMAT_CONV_MAX_PRECISION;
+					}
 				} else
 					adjust_precision = NO;
 			} else