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, 2 insertions, 1 deletions

diff --git a/lib/libc/stdio/xprintf_errno.c b/lib/libc/stdio/xprintf_errno.c
index 0c2be46..3c831d1 100644
--- a/lib/libc/stdio/xprintf_errno.c
+++ b/lib/libc/stdio/xprintf_errno.c
@@ -34,6 +34,7 @@
 #include <vis.h>
 #include <assert.h>
 #include <sys/time.h>
+#include "errlst.h"
 #include "printf.h"
 
 int
@@ -54,7 +55,7 @@ __printf_render_errno(struct __printf_io *io, const struct printf_info *pi __unu
 
 	ret = 0;
 	error = *((const int *)arg[0]);
-	if (error >= 0 && error < sys_nerr) {
+	if (error >= 0 && error < __hidden_sys_nerr) {
 		p = strerror(error);
 		return (__printf_out(io, pi, p, strlen(p)));
 	}