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Avoid use of strlen in getlogin_r (bug 22447)
- From: Joseph Myers <joseph at codesourcery dot com>
- To: <libc-alpha at sourceware dot org>
- Date: Wed, 22 Nov 2017 17:31:27 +0000
- Subject: Avoid use of strlen in getlogin_r (bug 22447)
- Authentication-results: sourceware.org; auth=none
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
<https://sourceware.org/ml/libc-alpha/2017-11/msg00797.html>, it fixes
the build for arm with mainline GCC.
2017-11-22 Joseph Myers <joseph@codesourcery.com>
[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.
diff --git a/sysdeps/unix/getlogin_r.c b/sysdeps/unix/getlogin_r.c
index 4a6a40e..ad8e911 100644
--- a/sysdeps/unix/getlogin_r.c
+++ b/sysdeps/unix/getlogin_r.c
@@ -80,7 +80,7 @@ __getlogin_r (char *name, size_t name_len)
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)
{
@@ -89,7 +89,8 @@ __getlogin_r (char *name, size_t name_len)
}
else
{
- memcpy (name, ut->ut_user, needed);
+ memcpy (name, ut->ut_user, needed - 1);
+ name[needed - 1] = 0;
result = 0;
}
}
--
Joseph S. Myers
joseph@codesourcery.com