posix: fix glob bugs with long login names

Current glob implementation allows unlimited user name for home
directory construction on GLOB_TILDE case.  To accomplish it glob
either construct a name on stack if size are small enough (based
on current alloca_used) or in heap otherwise.

This patch simplifies storage allocation by using the same scratch
buffer for both get_rlogin_r and getpwnam_r.

This also syncs with gnulib commit 064df0b (glob: fix bugs with long
login names).

Checked on x86_64-linux-gnu and on a build using build-many-glibcs.py
for all major architectures.

	* posix/glob.c (GET_LOGIN_NAME_MAX): Remove.
	(glob): Use the same scratch buffer for both getlogin_r and
	getpwnam_r.  Don’t require preallocation of the login name.  This
	simplifies storage allocation, and corrects the handling of
	long login names.

2 files changed, 37 insertions, 58 deletions

diff --git a/ChangeLog b/ChangeLog
index 39d1235c74..4c9334e839 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,6 +1,13 @@
 2017-09-08  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
 	[BZ #1062]
+	* posix/glob.c (GET_LOGIN_NAME_MAX): Remove.
+	(glob): Use the same scratch buffer for both getlogin_r and
+	getpwnam_r.  Don’t require preallocation of the login name.  This
+	simplifies storage allocation, and corrects the handling of
+	long login names.
+
+	[BZ #1062]
 	* posix/glob.c (glob): Port recent patches to platforms
 	lacking getpwnam_r.
 	(glob): Fix longstanding misuse of errno after getpwnam_r, which
diff --git a/posix/glob.c b/posix/glob.c
index ef620a1f0a..a47507a1cc 100644
--- a/posix/glob.c
+++ b/posix/glob.c
@@ -75,12 +75,6 @@
 #include <flexmember.h>
 #include <glob_internal.h>
 #include <scratch_buffer.h>
-
-#ifdef _SC_LOGIN_NAME_MAX
-# define GET_LOGIN_NAME_MAX()	sysconf (_SC_LOGIN_NAME_MAX)
-#else
-# define GET_LOGIN_NAME_MAX()	(-1)
-#endif
 
 static const char *next_brace_sub (const char *begin, int flags) __THROWNL;
 
@@ -610,67 +604,45 @@ glob (const char *pattern, int flags, int (*errfunc) (const char *, int),
 	      else
 		home_dir = "c:/users/default"; /* poor default */
 #else
-	      int success;
-	      char *name;
-	      int malloc_name = 0;
-	      size_t buflen = GET_LOGIN_NAME_MAX () + 1;
-
-	      if (buflen == 0)
-		/* 'sysconf' does not support _SC_LOGIN_NAME_MAX.  Try
-		   a moderate value.  */
-		buflen = 20;
-	      if (glob_use_alloca (alloca_used, buflen))
-		name = alloca_account (buflen, alloca_used);
-	      else
+	      int err;
+	      struct passwd *p;
+	      struct passwd pwbuf;
+	      struct scratch_buffer s;
+	      scratch_buffer_init (&s);
+	      while (true)
 		{
-		  name = malloc (buflen);
-		  if (name == NULL)
+		  p = NULL;
+		  err = __getlogin_r (s.data, s.length);
+		  if (err == 0)
 		    {
-		      retval = GLOB_NOSPACE;
-		      goto out;
-		    }
-		  malloc_name = 1;
-		}
-
-	      success = __getlogin_r (name, buflen) == 0;
-	      if (success)
-		{
-		  struct passwd *p;
-		  struct scratch_buffer pwtmpbuf;
-		  scratch_buffer_init (&pwtmpbuf);
 # if defined HAVE_GETPWNAM_R || defined _LIBC
-		  struct passwd pwbuf;
-
-		  while (getpwnam_r (name, &pwbuf,
-				     pwtmpbuf.data, pwtmpbuf.length, &p)
-			 == ERANGE)
-		    {
-		      if (!scratch_buffer_grow (&pwtmpbuf))
-			{
-			  retval = GLOB_NOSPACE;
-			  goto out;
-			}
-		    }
+		      size_t ssize = strlen (s.data) + 1;
+		      err = getpwnam_r (s.data, &pwbuf, s.data + ssize,
+					s.length - ssize, &p);
 # else
-		  p = getpwnam (name);
+		      p = getpwnam (s.data);
+		      if (p == NULL)
+			err = errno;
 # endif
-		  if (p != NULL)
+		    }
+		  if (err != ERANGE)
+		    break;
+		  if (!scratch_buffer_grow (&s))
 		    {
-		      home_dir = strdup (p->pw_dir);
-		      malloc_home_dir = 1;
-		      if (home_dir == NULL)
-			{
-			  scratch_buffer_free (&pwtmpbuf);
-			  retval = GLOB_NOSPACE;
-			  goto out;
-			}
+		      retval = GLOB_NOSPACE;
+		      goto out;
 		    }
-		  scratch_buffer_free (&pwtmpbuf);
 		}
-	      else
+	      if (err == 0)
+		{
+		  home_dir = strdup (p->pw_dir);
+		  malloc_home_dir = 1;
+		}
+	      scratch_buffer_free (&s);
+	      if (err == 0 && home_dir == NULL)
 		{
-		  if (__glibc_unlikely (malloc_name))
-		    free (name);
+		  retval = GLOB_NOSPACE;
+		  goto out;
 		}
 #endif /* WINDOWS32 */
 	    }