libc: Always use our own copy of sys_errlist and sys_nerr (.so only).

This ensures strerror() and friends continue to work correctly even if a
(non-PIE) executable linked against an older libc imports sys_errlist (which
causes sys_errlist to refer to the executable's copy with a size fixed when
that executable was linked).

The executable's use of sys_errlist remains broken because it uses the
current value of sys_nerr and may access past the bounds of the array.

Different from the message "Using sys_errlist from executables is not
ABI-stable" on freebsd-arch, this change does not affect the static library.
There seems no reason to prevent overriding the error messages in the static
library.

1 files changed, 5 insertions, 3 deletions

diff --git a/lib/libc/string/strerror.c b/lib/libc/string/strerror.c
index e11b351..1d7a385 100644
--- a/lib/libc/string/strerror.c
+++ b/lib/libc/string/strerror.c
@@ -42,6 +42,8 @@ __FBSDID("$FreeBSD$");
 #include <string.h>
 #include <stdio.h>
 
+#include "errlst.h"
+
 #define	UPREFIX		"Unknown error"
 
 /*
@@ -87,7 +89,7 @@ strerror_r(int errnum, char *strerrbuf, size_t buflen)
 	catd = catopen("libc", NL_CAT_LOCALE);
 #endif
 
-	if (errnum < 0 || errnum >= sys_nerr) {
+	if (errnum < 0 || errnum >= __hidden_sys_nerr) {
 		errstr(errnum,
 #if defined(NLS)
 			catgets(catd, 1, 0xffff, UPREFIX),
@@ -99,9 +101,9 @@ strerror_r(int errnum, char *strerrbuf, size_t buflen)
 	} else {
 		if (strlcpy(strerrbuf,
 #if defined(NLS)
-			catgets(catd, 1, errnum, sys_errlist[errnum]),
+			catgets(catd, 1, errnum, __hidden_sys_errlist[errnum]),
 #else
-			sys_errlist[errnum],
+			__hidden_sys_errlist[errnum],
 #endif
 			buflen) >= buflen)
 		retval = ERANGE;