Add error-throwing wrappers for the printf family of functions.

All known standard library implementations of these functions can fail with ENOMEM. A caller neglecting to check for failure would experience missing output, information exposure, or a crash. Check return values within wrappers and code, currently just snprintf.c, that bypasses the wrappers. The wrappers do not return after an error, so their callers need not check. Back-patch to 9.0 (all supported versions). Popular free software standard library implementations do take pains to bypass malloc() in simple cases, but they risk ENOMEM for floating point numbers, positional arguments, large field widths, and large precisions. No specification demands such caution, so this commit regards every call to a printf family function as a potential threat. Injecting the wrappers implicitly is a compromise between patch scope and design goals. I would prefer to edit each call site to name a wrapper explicitly. libpq and the ECPG libraries would, ideally, convey errors to the caller rather than abort(). All that would be painfully invasive for a back-patched security fix, hence this compromise. Security: CVE-2015-3166
2015-05-18 10:02:31 -04:00 · 2015-05-18 10:02:31 -04:00 · 16304a0134
parent cac18a76bb
commit 16304a0134
16 changed files with 300 additions and 93 deletions
--- a/src/include/port.h
+++ b/src/include/port.h
@ -126,12 +126,11 @@ extern unsigned char pg_tolower(unsigned char ch);
 extern unsigned char pg_ascii_toupper(unsigned char ch);
 extern unsigned char pg_ascii_tolower(unsigned char ch);

-#ifdef USE_REPL_SNPRINTF
-
 /*
- * Versions of libintl >= 0.13 try to replace printf() and friends with
- * macros to their own versions that understand the %$ format.  We do the
- * same, so disable their macros, if they exist.
+ * Capture macro-compatible calls to printf() and friends, and redirect them
+ * to wrappers that throw errors in lieu of reporting failure in a return
+ * value.  Versions of libintl >= 0.13 similarly redirect to versions that
+ * understand the %$ format, so disable libintl macros first.
 */
 #ifdef vsnprintf
 #undef vsnprintf
@ -155,6 +154,55 @@ extern unsigned char pg_ascii_tolower(unsigned char ch);
 #undef printf
 #endif

+extern int
+vsnprintf_throw_on_fail(char *str, size_t count, const char *fmt, va_list args)
+pg_attribute_printf(3, 0);
+extern int
+snprintf_throw_on_fail(char *str, size_t count, const char *fmt,...)
+pg_attribute_printf(3, 4);
+extern int
+vsprintf_throw_on_fail(char *str, const char *fmt, va_list args)
+pg_attribute_printf(2, 0);
+extern int
+sprintf_throw_on_fail(char *str, const char *fmt,...)
+pg_attribute_printf(2, 3);
+extern int
+vfprintf_throw_on_fail(FILE *stream, const char *fmt, va_list args)
+pg_attribute_printf(2, 0);
+extern int
+fprintf_throw_on_fail(FILE *stream, const char *fmt,...)
+pg_attribute_printf(2, 3);
+extern int
+printf_throw_on_fail(const char *fmt,...)
+pg_attribute_printf(1, 2);
+
+/*
+ *	The GCC-specific code below prevents the pg_attribute_printf above from
+ *	being replaced, and this is required because gcc doesn't know anything
+ *	about printf_throw_on_fail.
+ */
+#ifdef __GNUC__
+#define vsnprintf(...)	vsnprintf_throw_on_fail(__VA_ARGS__)
+#define snprintf(...)	snprintf_throw_on_fail(__VA_ARGS__)
+#define vsprintf(...)	vsprintf_throw_on_fail(__VA_ARGS__)
+#define sprintf(...)	sprintf_throw_on_fail(__VA_ARGS__)
+#define vfprintf(...)	vfprintf_throw_on_fail(__VA_ARGS__)
+#define fprintf(...)	fprintf_throw_on_fail(__VA_ARGS__)
+#define printf(...)		printf_throw_on_fail(__VA_ARGS__)
+#else
+#define vsnprintf		vsnprintf_throw_on_fail
+#define snprintf		snprintf_throw_on_fail
+#define vsprintf		vsprintf_throw_on_fail
+#define sprintf			sprintf_throw_on_fail
+#define vfprintf		vfprintf_throw_on_fail
+#define fprintf			fprintf_throw_on_fail
+#define printf			printf_throw_on_fail
+#endif
+
+#ifdef USE_REPL_SNPRINTF
+
+/* Code outside syswrap.c should not call these. */
+
 extern int	pg_vsnprintf(char *str, size_t count, const char *fmt, va_list args);
 extern int	pg_snprintf(char *str, size_t count, const char *fmt,...) pg_attribute_printf(3, 4);
 extern int	pg_vsprintf(char *str, const char *fmt, va_list args);
@ -163,28 +211,6 @@ extern int	pg_vfprintf(FILE *stream, const char *fmt, va_list args);
 extern int	pg_fprintf(FILE *stream, const char *fmt,...) pg_attribute_printf(2, 3);
 extern int	pg_printf(const char *fmt,...) pg_attribute_printf(1, 2);

-/*
- *	The GCC-specific code below prevents the pg_attribute_printf above from
- *	being replaced, and this is required because gcc doesn't know anything
- *	about pg_printf.
- */
-#ifdef __GNUC__
-#define vsnprintf(...)	pg_vsnprintf(__VA_ARGS__)
-#define snprintf(...)	pg_snprintf(__VA_ARGS__)
-#define vsprintf(...)	pg_vsprintf(__VA_ARGS__)
-#define sprintf(...)	pg_sprintf(__VA_ARGS__)
-#define vfprintf(...)	pg_vfprintf(__VA_ARGS__)
-#define fprintf(...)	pg_fprintf(__VA_ARGS__)
-#define printf(...)		pg_printf(__VA_ARGS__)
-#else
-#define vsnprintf		pg_vsnprintf
-#define snprintf		pg_snprintf
-#define vsprintf		pg_vsprintf
-#define sprintf			pg_sprintf
-#define vfprintf		pg_vfprintf
-#define fprintf			pg_fprintf
-#define printf			pg_printf
-#endif
 #endif   /* USE_REPL_SNPRINTF */

 #if defined(WIN32)
--- a/src/interfaces/ecpg/compatlib/Makefile
+++ b/src/interfaces/ecpg/compatlib/Makefile
@ -48,6 +48,7 @@ submake-pgtypeslib:
 # Shared library stuff
 include $(top_srcdir)/src/Makefile.shlib

+# XXX This library uses no symbols from snprintf.c.
 snprintf.c: % : $(top_srcdir)/src/port/%
 	rm -f $@ && $(LN_S) $< .

--- a/src/interfaces/ecpg/ecpglib/.gitignore
+++ b/src/interfaces/ecpg/ecpglib/.gitignore
@ -5,6 +5,7 @@
 /pgstrcasecmp.c
 /snprintf.c
 /strlcpy.c
+/syswrap.c
 /thread.c
 /win32setlocale.c
 /isinf.c
--- a/src/interfaces/ecpg/ecpglib/Makefile
+++ b/src/interfaces/ecpg/ecpglib/Makefile
@ -26,7 +26,7 @@ override CFLAGS += $(PTHREAD_CFLAGS)
 LIBS := $(filter-out -lpgport, $(LIBS))

 OBJS= execute.o typename.o descriptor.o sqlda.o data.o error.o prepare.o memory.o \
-	connect.o misc.o path.o pgstrcasecmp.o \
+	connect.o misc.o path.o pgstrcasecmp.o syswrap.o \
 	$(filter snprintf.o strlcpy.o win32setlocale.o isinf.o, $(LIBOBJS)) $(WIN32RES)

 # thread.c is needed only for non-WIN32 implementation of path.c
@ -55,7 +55,7 @@ include $(top_srcdir)/src/Makefile.shlib
 # necessarily use the same object files as the backend uses. Instead,
 # symlink the source files in here and build our own object file.

-path.c pgstrcasecmp.c snprintf.c strlcpy.c thread.c win32setlocale.c isinf.c: % : $(top_srcdir)/src/port/%
+path.c pgstrcasecmp.c snprintf.c strlcpy.c syswrap.c thread.c win32setlocale.c isinf.c: % : $(top_srcdir)/src/port/%
 	rm -f $@ && $(LN_S) $< .

 misc.o: misc.c $(top_builddir)/src/port/pg_config_paths.h
@ -72,6 +72,6 @@ uninstall: uninstall-lib

 clean distclean: clean-lib
 	rm -f $(OBJS)
-	rm -f path.c pgstrcasecmp.c snprintf.c strlcpy.c thread.c win32setlocale.c isinf.c
+	rm -f path.c pgstrcasecmp.c snprintf.c strlcpy.c syswrap.c thread.c win32setlocale.c isinf.c

 maintainer-clean: distclean maintainer-clean-lib
--- a/src/interfaces/ecpg/pgtypeslib/.gitignore
+++ b/src/interfaces/ecpg/pgtypeslib/.gitignore
@ -4,3 +4,4 @@
 /pgstrcasecmp.c
 /rint.c
 /snprintf.c
+/syswrap.c
--- a/src/interfaces/ecpg/pgtypeslib/Makefile
+++ b/src/interfaces/ecpg/pgtypeslib/Makefile
@ -30,7 +30,7 @@ SHLIB_LINK += -lm
 SHLIB_EXPORTS = exports.txt

 OBJS= numeric.o datetime.o common.o dt_common.o timestamp.o interval.o \
-	pgstrcasecmp.o \
+	pgstrcasecmp.o syswrap.o \
 	$(filter rint.o snprintf.o, $(LIBOBJS)) $(WIN32RES)

 all: all-lib
@ -43,7 +43,7 @@ include $(top_srcdir)/src/Makefile.shlib
 # necessarily use the same object files as the backend uses. Instead,
 # symlink the source files in here and build our own object file.

-pgstrcasecmp.c rint.c snprintf.c: % : $(top_srcdir)/src/port/%
+pgstrcasecmp.c rint.c snprintf.c syswrap.c: % : $(top_srcdir)/src/port/%
 	rm -f $@ && $(LN_S) $< .

 install: all installdirs install-lib
@ -53,6 +53,6 @@ installdirs: installdirs-lib
 uninstall: uninstall-lib

 clean distclean: clean-lib
-	rm -f $(OBJS) pgstrcasecmp.c rint.c snprintf.c
+	rm -f $(OBJS) pgstrcasecmp.c rint.c snprintf.c syswrap.c

 maintainer-clean: distclean maintainer-clean-lib
--- a/src/interfaces/libpq/.gitignore
+++ b/src/interfaces/libpq/.gitignore
@ -13,6 +13,7 @@
 /strerror.c
 /strlcpy.c
 /system.c
+/syswrap.c
 /thread.c
 /win32error.c
 /win32setlocale.c
--- a/src/interfaces/libpq/Makefile
+++ b/src/interfaces/libpq/Makefile
@ -36,7 +36,7 @@ OBJS=	fe-auth.o fe-connect.o fe-exec.o fe-misc.o fe-print.o fe-lobj.o \
 	libpq-events.o
 # libpgport C files we always use
 OBJS += chklocale.o inet_net_ntop.o noblock.o pgstrcasecmp.o pqsignal.o \
-	thread.o
+	syswrap.o thread.o
 # libpgport C files that are needed if identified by configure
 OBJS += $(filter crypt.o getaddrinfo.o getpeereid.o inet_aton.o open.o system.o snprintf.o strerror.o strlcpy.o win32error.o win32setlocale.o, $(LIBOBJS))
 # backend/libpq
@ -93,7 +93,7 @@ backend_src = $(top_srcdir)/src/backend
 # For some libpgport modules, this only happens if configure decides
 # the module is needed (see filter hack in OBJS, above).

-chklocale.c crypt.c getaddrinfo.c getpeereid.c inet_aton.c inet_net_ntop.c noblock.c open.c system.c pgsleep.c pgstrcasecmp.c pqsignal.c snprintf.c strerror.c strlcpy.c thread.c win32error.c win32setlocale.c: % : $(top_srcdir)/src/port/%
+chklocale.c crypt.c getaddrinfo.c getpeereid.c inet_aton.c inet_net_ntop.c noblock.c open.c system.c pgsleep.c pgstrcasecmp.c pqsignal.c snprintf.c strerror.c strlcpy.c syswrap.c thread.c win32error.c win32setlocale.c: % : $(top_srcdir)/src/port/%
 	rm -f $@ && $(LN_S) $< .

 ip.c md5.c: % : $(backend_src)/libpq/%
@ -145,7 +145,7 @@ clean distclean: clean-lib
 # Might be left over from a Win32 client-only build
 	rm -f pg_config_paths.h
 	rm -f inet_net_ntop.c noblock.c pgstrcasecmp.c pqsignal.c thread.c
-	rm -f chklocale.c crypt.c getaddrinfo.c getpeereid.c inet_aton.c open.c system.c snprintf.c strerror.c strlcpy.c win32error.c win32setlocale.c
+	rm -f chklocale.c crypt.c getaddrinfo.c getpeereid.c inet_aton.c open.c system.c snprintf.c strerror.c strlcpy.c syswrap.c win32error.c win32setlocale.c
 	rm -f pgsleep.c
 	rm -f md5.c ip.c
 	rm -f encnames.c wchar.c
--- a/src/interfaces/libpq/bcc32.mak
+++ b/src/interfaces/libpq/bcc32.mak
@ -107,6 +107,7 @@ CLEAN :
 	-@erase "$(INTDIR)\pgsleep.obj"
 	-@erase "$(INTDIR)\open.obj"
 	-@erase "$(INTDIR)\system.obj"
+	-@erase "$(INTDIR)\syswrap.obj"
 	-@erase "$(INTDIR)\win32error.obj"
 	-@erase "$(OUTDIR)\$(OUTFILENAME).lib"
 	-@erase "$(OUTDIR)\$(OUTFILENAME)dll.lib"
@ -151,6 +152,7 @@ LIB32_OBJS= \
 	"$(INTDIR)\pgsleep.obj" \
 	"$(INTDIR)\open.obj" \
 	"$(INTDIR)\system.obj" \
+	"$(INTDIR)\syswrap.obj" \
 	"$(INTDIR)\win32error.obj" \
 	"$(INTDIR)\pthread-win32.obj"

@ -302,6 +304,11 @@ LINK32_FLAGS = -Gn -L$(BCB)\lib;$(INTDIR); -x -Tpd -v
 	$(CPP_PROJ) /I"." ..\..\port\system.c
 <<

+"$(INTDIR)\syswrap.obj" : ..\..\port\syswrap.c
+	$(CPP) @<<
+	$(CPP_PROJ) ..\..\port\syswrap.c
+<<
+
 "$(INTDIR)\win32error.obj" : ..\..\port\win32error.c
 	$(CPP) @<<
 	$(CPP_PROJ) /I"." ..\..\port\win32error.c
--- a/src/interfaces/libpq/win32.mak
+++ b/src/interfaces/libpq/win32.mak
@ -114,6 +114,7 @@ CLEAN :
 	-@erase "$(INTDIR)\pgsleep.obj"
 	-@erase "$(INTDIR)\open.obj"
 	-@erase "$(INTDIR)\system.obj"
+	-@erase "$(INTDIR)\syswrap.obj"
 	-@erase "$(INTDIR)\win32error.obj"
 	-@erase "$(INTDIR)\win32setlocale.obj"
 	-@erase "$(OUTDIR)\$(OUTFILENAME).lib"
@ -164,6 +165,7 @@ LIB32_OBJS= \
 	"$(INTDIR)\pgsleep.obj" \
 	"$(INTDIR)\open.obj" \
 	"$(INTDIR)\system.obj" \
+	"$(INTDIR)\syswrap.obj" \
 	"$(INTDIR)\win32error.obj" \
 	"$(INTDIR)\win32setlocale.obj" \
 	"$(INTDIR)\pthread-win32.obj"
@ -348,6 +350,11 @@ LINK32_OBJS= \
 	$(CPP_PROJ) /I"." ..\..\port\system.c
 <<

+"$(INTDIR)\syswrap.obj" : ..\..\port\syswrap.c
+	$(CPP) @<<
+	$(CPP_PROJ) ..\..\port\syswrap.c
+<<
+
 "$(INTDIR)\win32error.obj" : ..\..\port\win32error.c
 	$(CPP) @<<
 	$(CPP_PROJ) /I"." ..\..\port\win32error.c
--- a/src/pl/plperl/plperl.h
+++ b/src/pl/plperl/plperl.h
@ -37,10 +37,8 @@
 * So we undefine them here and redefine them after it's done its dirty deed.
 */

-#ifdef USE_REPL_SNPRINTF
 #undef snprintf
 #undef vsnprintf
-#endif


 /* required for perl API */
@ -49,7 +47,6 @@
 #include "XSUB.h"

 /* put back our snprintf and vsnprintf */
-#ifdef USE_REPL_SNPRINTF
 #ifdef snprintf
 #undef snprintf
 #endif
@ -57,13 +54,12 @@
 #undef vsnprintf
 #endif
 #ifdef __GNUC__
-#define vsnprintf(...)	pg_vsnprintf(__VA_ARGS__)
-#define snprintf(...)	pg_snprintf(__VA_ARGS__)
+#define vsnprintf(...)	vsnprintf_throw_on_fail(__VA_ARGS__)
+#define snprintf(...)	snprintf_throw_on_fail(__VA_ARGS__)
 #else
-#define vsnprintf		pg_vsnprintf
-#define snprintf		pg_snprintf
+#define vsnprintf		vsnprintf_throw_on_fail
+#define snprintf		snprintf_throw_on_fail
 #endif   /* __GNUC__ */
-#endif   /* USE_REPL_SNPRINTF */

 /* perl version and platform portability */
 #define NEED_eval_pv
--- a/src/pl/plpython/plpython.h
+++ b/src/pl/plpython/plpython.h
@ -35,10 +35,8 @@
 * So we undefine them here and redefine them after it's done its dirty deed.
 */

-#ifdef USE_REPL_SNPRINTF
 #undef snprintf
 #undef vsnprintf
-#endif

 #if defined(_MSC_VER) && defined(_DEBUG)
 /* Python uses #pragma to bring in a non-default libpython on VC++ if
@ -125,7 +123,6 @@ typedef int Py_ssize_t;
 #include <eval.h>

 /* put back our snprintf and vsnprintf */
-#ifdef USE_REPL_SNPRINTF
 #ifdef snprintf
 #undef snprintf
 #endif
@ -133,13 +130,12 @@ typedef int Py_ssize_t;
 #undef vsnprintf
 #endif
 #ifdef __GNUC__
-#define vsnprintf(...)	pg_vsnprintf(__VA_ARGS__)
-#define snprintf(...)	pg_snprintf(__VA_ARGS__)
+#define vsnprintf(...)	vsnprintf_throw_on_fail(__VA_ARGS__)
+#define snprintf(...)	snprintf_throw_on_fail(__VA_ARGS__)
 #else
-#define vsnprintf				pg_vsnprintf
-#define snprintf				pg_snprintf
+#define vsnprintf		vsnprintf_throw_on_fail
+#define snprintf		snprintf_throw_on_fail
 #endif   /* __GNUC__ */
-#endif   /* USE_REPL_SNPRINTF */

 /*
 * Used throughout, and also by the Python 2/3 porting layer, so it's easier to
--- a/src/port/Makefile
+++ b/src/port/Makefile
@ -33,7 +33,7 @@ LIBS += $(PTHREAD_LIBS)
 OBJS = $(LIBOBJS) $(PG_CRC32C_OBJS) chklocale.o erand48.o inet_net_ntop.o \
 	noblock.o path.o pgcheckdir.o pgmkdirp.o pgsleep.o \
 	pgstrcasecmp.o pqsignal.o \
-	qsort.o qsort_arg.o quotes.o sprompt.o tar.o thread.o
+	qsort.o qsort_arg.o quotes.o sprompt.o syswrap.o tar.o thread.o

 # foo_srv.o and foo.o are both built from foo.c, but only foo.o has -DFRONTEND
 OBJS_SRV = $(OBJS:%.o=%_srv.o)
--- a/src/port/snprintf.c
+++ b/src/port/snprintf.c
@ -114,6 +114,7 @@ typedef struct
 	/* bufend == NULL is for sprintf, where we assume buf is big enough */
 	FILE	   *stream;			/* eventual output destination, or NULL */
 	int			nchars;			/* # chars already sent to stream */
+	bool		failed;			/* call is a failure; errno is set */
 } PrintfTarget;

 /*
@ -143,7 +144,7 @@ typedef union


 static void flushbuffer(PrintfTarget *target);
-static int	dopr(PrintfTarget *target, const char *format, va_list args);
+static void dopr(PrintfTarget *target, const char *format, va_list args);


 int
@ -157,14 +158,10 @@ pg_vsnprintf(char *str, size_t count, const char *fmt, va_list args)
 	target.bufend = str + count - 1;
 	target.stream = NULL;
 	/* target.nchars is unused in this case */
-	if (dopr(&target, fmt, args))
-	{
-		*(target.bufptr) = '\0';
-		errno = EINVAL;			/* bad format */
-		return -1;
-	}
+	target.failed = false;
+	dopr(&target, fmt, args);
 	*(target.bufptr) = '\0';
-	return target.bufptr - target.bufstart;
+	return target.failed ? -1 : (target.bufptr - target.bufstart);
 }

 int
@ -190,14 +187,10 @@ pg_vsprintf(char *str, const char *fmt, va_list args)
 	target.bufend = NULL;
 	target.stream = NULL;
 	/* target.nchars is unused in this case */
-	if (dopr(&target, fmt, args))
-	{
-		*(target.bufptr) = '\0';
-		errno = EINVAL;			/* bad format */
-		return -1;
-	}
+	target.failed = false;
+	dopr(&target, fmt, args);
 	*(target.bufptr) = '\0';
-	return target.bufptr - target.bufstart;
+	return target.failed ? -1 : (target.bufptr - target.bufstart);
 }

 int
@ -227,14 +220,11 @@ pg_vfprintf(FILE *stream, const char *fmt, va_list args)
 	target.bufend = buffer + sizeof(buffer) - 1;
 	target.stream = stream;
 	target.nchars = 0;
-	if (dopr(&target, fmt, args))
-	{
-		errno = EINVAL;			/* bad format */
-		return -1;
-	}
+	target.failed = false;
+	dopr(&target, fmt, args);
 	/* dump any remaining buffer contents */
 	flushbuffer(&target);
-	return target.nchars;
+	return target.failed ? -1 : target.nchars;
 }

 int
@ -261,14 +251,24 @@ pg_printf(const char *fmt,...)
 	return len;
 }

-/* call this only when stream is defined */
+/*
+ * Attempt to write the entire buffer to target->stream; discard the entire
+ * buffer in any case.  Call this only when target->stream is defined.
+ */
 static void
 flushbuffer(PrintfTarget *target)
 {
 	size_t		nc = target->bufptr - target->bufstart;

-	if (nc > 0)
-		target->nchars += fwrite(target->bufstart, 1, nc, target->stream);
+	if (!target->failed && nc > 0)
+	{
+		size_t		written;
+
+		written = fwrite(target->bufstart, 1, nc, target->stream);
+		target->nchars += written;
+		if (written != nc)
+			target->failed = true;
+	}
 	target->bufptr = target->bufstart;
 }

@ -295,7 +295,7 @@ static void trailing_pad(int *padlen, PrintfTarget *target);
 /*
 * dopr(): poor man's version of doprintf
 */
-static int
+static void
 dopr(PrintfTarget *target, const char *format, va_list args)
 {
 	const char *format_start = format;
@ -372,12 +372,12 @@ nextch1:
 			case '$':
 				have_dollar = true;
 				if (accum <= 0 || accum > NL_ARGMAX)
-					return -1;
+					goto bad_format;
 				if (afterstar)
 				{
 					if (argtypes[accum] &&
 						argtypes[accum] != ATYPE_INT)
-						return -1;
+						goto bad_format;
 					argtypes[accum] = ATYPE_INT;
 					last_dollar = Max(last_dollar, accum);
 					afterstar = false;
@ -427,7 +427,7 @@ nextch1:
 						atype = ATYPE_INT;
 					if (argtypes[fmtpos] &&
 						argtypes[fmtpos] != atype)
-						return -1;
+						goto bad_format;
 					argtypes[fmtpos] = atype;
 					last_dollar = Max(last_dollar, fmtpos);
 				}
@ -439,7 +439,7 @@ nextch1:
 				{
 					if (argtypes[fmtpos] &&
 						argtypes[fmtpos] != ATYPE_INT)
-						return -1;
+						goto bad_format;
 					argtypes[fmtpos] = ATYPE_INT;
 					last_dollar = Max(last_dollar, fmtpos);
 				}
@ -452,7 +452,7 @@ nextch1:
 				{
 					if (argtypes[fmtpos] &&
 						argtypes[fmtpos] != ATYPE_CHARPTR)
-						return -1;
+						goto bad_format;
 					argtypes[fmtpos] = ATYPE_CHARPTR;
 					last_dollar = Max(last_dollar, fmtpos);
 				}
@ -468,7 +468,7 @@ nextch1:
 				{
 					if (argtypes[fmtpos] &&
 						argtypes[fmtpos] != ATYPE_DOUBLE)
-						return -1;
+						goto bad_format;
 					argtypes[fmtpos] = ATYPE_DOUBLE;
 					last_dollar = Max(last_dollar, fmtpos);
 				}
@ -489,7 +489,7 @@ nextch1:

 	/* Per spec, you use either all dollar or all not. */
 	if (have_dollar && have_non_dollar)
-		return -1;
+		goto bad_format;

 	/*
 	 * In dollar mode, collect the arguments in physical order.
@ -499,7 +499,7 @@ nextch1:
 		switch (argtypes[i])
 		{
 			case ATYPE_NONE:
-				return -1;		/* invalid format */
+				goto bad_format;
 			case ATYPE_INT:
 				argvalues[i].i = va_arg(args, int);
 				break;
@ -524,6 +524,9 @@ nextch1:
 	format = format_start;
 	while ((ch = *format++) != '\0')
 	{
+		if (target->failed)
+			break;
+
 		if (ch != '%')
 		{
 			dopr_outch(ch, target);
@ -781,7 +784,11 @@ nextch2:
 		}
 	}

-	return 0;
+	return;
+
+bad_format:
+	errno = EINVAL;
+	target->failed = true;
 }

 static size_t
@ -831,8 +838,10 @@ fmtptr(void *value, PrintfTarget *target)

 	/* we rely on regular C library's sprintf to do the basic conversion */
 	vallen = sprintf(convert, "%p", value);
-
-	dostr(convert, vallen, target);
+	if (vallen < 0)
+		target->failed = true;
+	else
+		dostr(convert, vallen, target);
 }

 static void
@ -965,16 +974,19 @@ fmtfloat(double value, char type, int forcesign, int leftjust,

 	if (pointflag)
 	{
-		sprintf(fmt, "%%.%d%c", prec, type);
+		if (sprintf(fmt, "%%.%d%c", prec, type) < 0)
+			goto fail;
 		zeropadlen = precision - prec;
 	}
-	else
-		sprintf(fmt, "%%%c", type);
+	else if (sprintf(fmt, "%%%c", type) < 0)
+		goto fail;

 	if (!isnan(value) && adjust_sign((value < 0), forcesign, &signvalue))
 		value = -value;

 	vallen = sprintf(convert, fmt, value);
+	if (vallen < 0)
+		goto fail;

 	/* If it's infinity or NaN, forget about doing any zero-padding */
 	if (zeropadlen > 0 && !isdigit((unsigned char) convert[vallen - 1]))
@ -1014,6 +1026,10 @@ fmtfloat(double value, char type, int forcesign, int leftjust,
 	}

 	trailing_pad(&padlen, target);
+	return;
+
+fail:
+	target->failed = true;
 }

 static void
--- a/src/port/syswrap.c
+++ b/src/port/syswrap.c
@ -0,0 +1,155 @@
+/*-------------------------------------------------------------------------
+ *
+ * syswrap.c
+ *	  error-throwing wrappers around POSIX functions that rarely fail
+ *
+ * Portions Copyright (c) 1996-2015, PostgreSQL Global Development Group
+ *
+ *
+ * IDENTIFICATION
+ *	  src/port/syswrap.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#ifndef FRONTEND
+#include "postgres.h"
+#else
+#include "postgres_fe.h"
+#endif
+
+/* Prevent recursion */
+#undef	vsnprintf
+#undef	snprintf
+#undef	vsprintf
+#undef	sprintf
+#undef	vfprintf
+#undef	fprintf
+#undef	printf
+
+/* When the libc primitives are lacking, use our own. */
+#ifdef USE_REPL_SNPRINTF
+#ifdef __GNUC__
+#define vsnprintf(...)	pg_vsnprintf(__VA_ARGS__)
+#define snprintf(...)	pg_snprintf(__VA_ARGS__)
+#define vsprintf(...)	pg_vsprintf(__VA_ARGS__)
+#define sprintf(...)	pg_sprintf(__VA_ARGS__)
+#define vfprintf(...)	pg_vfprintf(__VA_ARGS__)
+#define fprintf(...)	pg_fprintf(__VA_ARGS__)
+#define printf(...)		pg_printf(__VA_ARGS__)
+#else
+#define vsnprintf		pg_vsnprintf
+#define snprintf		pg_snprintf
+#define vsprintf		pg_vsprintf
+#define sprintf			pg_sprintf
+#define vfprintf		pg_vfprintf
+#define fprintf			pg_fprintf
+#define printf			pg_printf
+#endif
+#endif   /* USE_REPL_SNPRINTF */
+
+/*
+ * We abort() in the frontend, rather than exit(), because libpq in particular
+ * has no business calling exit().  These failures had better be rare.
+ */
+#ifdef FRONTEND
+#define LIB_ERR(func) \
+do { \
+	int discard = fprintf(stderr, "%s failed: %s\n", func, strerror(errno)); \
+	(void) discard; \
+	abort(); \
+} while (0)
+#else
+#define LIB_ERR(func) elog(ERROR, "%s failed: %m", func)
+#endif
+
+int
+vsnprintf_throw_on_fail(char *str, size_t count, const char *fmt, va_list args)
+{
+	int			save_errno;
+	int			ret;
+
+	/*
+	 * On HP-UX B.11.31, a call that truncates output returns -1 without
+	 * setting errno.  (SUSv2 allowed this until the approval of Base Working
+	 * Group Resolution BWG98-006.)  We could avoid the save and restore of
+	 * errno on most platforms.
+	 */
+	save_errno = errno;
+	errno = 0;
+	ret = vsnprintf(str, count, fmt, args);
+	if (ret < 0 && errno != 0)
+		LIB_ERR("vsnprintf");
+	errno = save_errno;
+	return ret;
+}
+
+int
+snprintf_throw_on_fail(char *str, size_t count, const char *fmt,...)
+{
+	int			ret;
+	va_list		args;
+
+	va_start(args, fmt);
+	ret = vsnprintf_throw_on_fail(str, count, fmt, args);
+	va_end(args);
+	return ret;
+}
+
+int
+vsprintf_throw_on_fail(char *str, const char *fmt, va_list args)
+{
+	int			ret;
+
+	ret = vsprintf(str, fmt, args);
+	if (ret < 0)
+		LIB_ERR("vsprintf");
+	return ret;
+}
+
+int
+sprintf_throw_on_fail(char *str, const char *fmt,...)
+{
+	int			ret;
+	va_list		args;
+
+	va_start(args, fmt);
+	ret = vsprintf_throw_on_fail(str, fmt, args);
+	va_end(args);
+	return ret;
+}
+
+int
+vfprintf_throw_on_fail(FILE *stream, const char *fmt, va_list args)
+{
+	int			ret;
+
+	ret = vfprintf(stream, fmt, args);
+	if (ret < 0)
+		LIB_ERR("vfprintf");
+	return ret;
+}
+
+int
+fprintf_throw_on_fail(FILE *stream, const char *fmt,...)
+{
+	int			ret;
+	va_list		args;
+
+	va_start(args, fmt);
+	ret = vfprintf_throw_on_fail(stream, fmt, args);
+	va_end(args);
+	return ret;
+}
+
+int
+printf_throw_on_fail(const char *fmt,...)
+{
+	int			ret;
+	va_list		args;
+
+	va_start(args, fmt);
+	ret = vfprintf_throw_on_fail(stdout, fmt, args);
+	va_end(args);
+	return ret;
+}
--- a/src/tools/msvc/Mkvcbuild.pm
+++ b/src/tools/msvc/Mkvcbuild.pm
@ -91,7 +91,7 @@ sub mkvcbuild
 	  erand48.c snprintf.c strlcat.c strlcpy.c dirmod.c noblock.c path.c
 	  pgcheckdir.c pgmkdirp.c pgsleep.c pgstrcasecmp.c pqsignal.c
 	  mkdtemp.c qsort.c qsort_arg.c quotes.c system.c
-	  sprompt.c tar.c thread.c getopt.c getopt_long.c dirent.c
+	  sprompt.c syswrap.c tar.c thread.c getopt.c getopt_long.c dirent.c
 	  win32env.c win32error.c win32setlocale.c);

 	push(@pgportfiles, 'rint.c') if ($vsVersion < '12.00');