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Avoid use of strlen in getlogin_r (bug 22447).

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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.
This commit is contained in:
Joseph Myers
2017-11-22 18:44:23 +00:00
parent 4b7af5fca7
commit 4bae615022
2 changed files with 10 additions and 2 deletions
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5
sysdeps/unix/getlogin_r.c
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@ -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;
}
}