From 913c09becd9df89dbd9b9f386e7f35c240d5efe8 Mon Sep 17 00:00:00 2001 From: Bruno Haible Date: Fri, 19 Oct 2007 01:50:42 +0200 Subject: [PATCH] Don't use %n on glibc >= 2.3 systems. --- ChangeLog | 5 +++++ lib/vasnprintf.c | 12 ++++++++++++ 2 files changed, 17 insertions(+) diff --git a/ChangeLog b/ChangeLog index 73ac493f8..2a3499900 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,8 @@ +2007-10-18 Bruno Haible + + * m4/vasnprintf.m4 (VASNPRINTF): Don't use %n on glibc >= 2.3 systems. + Reported by Jim Meyering. + 2007-10-18 Eric Blake * modules/filenamecat-tests (Makefile.am): Link against -lintl. diff --git a/lib/vasnprintf.c b/lib/vasnprintf.c index f56382334..5d818aa64 100644 --- a/lib/vasnprintf.c +++ b/lib/vasnprintf.c @@ -3385,9 +3385,21 @@ VASNPRINTF (DCHAR_T *resultbuf, size_t *lengthp, #endif *fbp = dp->conversion; #if USE_SNPRINTF +# if !(__GLIBC__ > 2 || (__GLIBC__ == 2 && __GLIBC_MINOR__ >= 3)) fbp[1] = '%'; fbp[2] = 'n'; fbp[3] = '\0'; +# else + /* On glibc2 systems from glibc >= 2.3 - probably also older + ones - we know that snprintf's returns value conforms to + ISO C 99: the gl_SNPRINTF_DIRECTIVE_N test passes. + Therefore we can avoid using %n in this situation. + On glibc2 systems from 2004-10-18 or newer, the use of %n + in format strings in writable memory may crash the program + (if compiled with _FORTIFY_SOURCE=2), so we should avoid it + in this situation. */ + fbp[1] = '\0'; +# endif #else fbp[1] = '\0'; #endif -- 2.11.0