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commit 4bae615022cb5a5da79ccda83cc6c9ba9f2d479c
Author: Joseph Myers <joseph@codesourcery.com>
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
<https://sourceware.org/ml/libc-alpha/2017-11/msg00797.html>, 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;
}
}
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