Merge 'master' into noverlay

1 files changed, 48 insertions, 18 deletions

diff --git a/lib/readlink.c b/lib/readlink.c
index cd9604b224c..ed03cc8ded1 100644
--- a/lib/readlink.c
+++ b/lib/readlink.c
@@ -1,17 +1,17 @@
-/* Stub for readlink().
-   Copyright (C) 2003-2007, 2009-2017 Free Software Foundation, Inc.
+/* Read the contents of a symbolic link.
+   Copyright (C) 2003-2007, 2009-2022 Free Software Foundation, Inc.
 
-   This program is free software: you can redistribute it and/or modify
-   it under the terms of the GNU General Public License as published by
-   the Free Software Foundation; either version 3 of the License, or
-   (at your option) any later version.
+   This file is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
 
-   This program is distributed in the hope that it will be useful,
+   This file is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-   GNU General Public License for more details.
+   GNU Lesser General Public License for more details.
 
-   You should have received a copy of the GNU General Public License
+   You should have received a copy of the GNU Lesser General Public License
    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
 
 #include <config.h>
@@ -29,15 +29,15 @@
    such as DJGPP 2.03 and mingw32.  */
 
 ssize_t
-readlink (const char *name, char *buf _GL_UNUSED,
-          size_t bufsize _GL_UNUSED)
+readlink (char const *file, _GL_UNUSED char *buf,
+          _GL_UNUSED size_t bufsize)
 {
   struct stat statbuf;
 
   /* In general we should use lstat() here, not stat().  But on platforms
      without symbolic links, lstat() - if it exists - would be equivalent to
      stat(), therefore we can use stat().  This saves us a configure check.  */
-  if (stat (name, &statbuf) >= 0)
+  if (stat (file, &statbuf) >= 0)
     errno = EINVAL;
   return -1;
 }
@@ -51,24 +51,54 @@ readlink (const char *name, char *buf _GL_UNUSED,
    for Solaris 9.  */
 
 ssize_t
-rpl_readlink (const char *name, char *buf, size_t bufsize)
+rpl_readlink (char const *file, char *buf, size_t bufsize)
 {
 # if READLINK_TRAILING_SLASH_BUG
-  size_t len = strlen (name);
-  if (len && name[len - 1] == '/')
+  size_t file_len = strlen (file);
+  if (file_len && file[file_len - 1] == '/')
     {
-      /* Even if name without the slash is a symlink to a directory,
+      /* Even if FILE without the slash is a symlink to a directory,
          both lstat() and stat() must resolve the trailing slash to
          the directory rather than the symlink.  We can therefore
          safely use stat() to distinguish between EINVAL and
          ENOTDIR/ENOENT, avoiding extra overhead of rpl_lstat().  */
       struct stat st;
-      if (stat (name, &st) == 0)
+      if (stat (file, &st) == 0 || errno == EOVERFLOW)
         errno = EINVAL;
       return -1;
     }
 # endif /* READLINK_TRAILING_SLASH_BUG */
-  return readlink (name, buf, bufsize);
+
+  ssize_t r = readlink (file, buf, bufsize);
+
+# if READLINK_TRUNCATE_BUG
+  if (r < 0 && errno == ERANGE)
+    {
+      /* Try again with a bigger buffer.  This is just for test cases;
+         real code invariably discards short reads.  */
+      char stackbuf[4032];
+      r = readlink (file, stackbuf, sizeof stackbuf);
+      if (r < 0)
+        {
+          if (errno == ERANGE)
+            {
+              /* Clear the buffer, which is good enough for real code.
+                 Thankfully, no test cases try short reads of enormous
+                 symlinks and what would be the point anyway?  */
+              r = bufsize;
+              memset (buf, 0, r);
+            }
+        }
+      else
+        {
+          if (bufsize < r)
+            r = bufsize;
+          memcpy (buf, stackbuf, r);
+        }
+    }
+# endif
+
+  return r;
 }
 
 #endif /* HAVE_READLINK */