commit 4bae615022cb5a5da79ccda83cc6c9ba9f2d479c Author: Joseph Myers Date: Wed Nov 22 18:44:23 2017 +0000 Avoid use of strlen in getlogin_r (bug 22447). Building glibc with current mainline GCC fails, among other reasons, because of an error for use of strlen on the nonstring ut_user field. This patch changes the problem code in getlogin_r to use __strnlen instead. It also needs to set the trailing NUL byte of the result explicitly, because of the case where ut_user does not have such a trailing NUL byte (but the result should always have one). Tested for x86_64. Also tested that, in conjunction with , it fixes the build for arm with mainline GCC. [BZ #22447] * sysdeps/unix/getlogin_r.c (__getlogin_r): Use __strnlen not strlen to compute length of ut_user and set trailing NUL byte of result explicitly. --- sysdeps/unix/getlogin_r.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/sysdeps/unix/getlogin_r.c +++ b/sysdeps/unix/getlogin_r.c @@ -83,7 +83,7 @@ if (result == 0) { - size_t needed = strlen (ut->ut_user) + 1; + size_t needed = __strnlen (ut->ut_user, UT_NAMESIZE) + 1; if (needed > name_len) { @@ -92,7 +92,8 @@ } else { - memcpy (name, ut->ut_user, needed); + memcpy (name, ut->ut_user, needed - 1); + name[needed - 1] = 0; result = 0; } }