[PATCH 1/6] canonicalize-lgpl: fix EOVERFLOW bug

[Paul Eggert]

* lib/canonicalize-lgpl.c: Do not include <sys/stat.h>.
(__realpath): Do not use lstat.  Just use readlink, as this
suffices and it avoids the EOVERFLOW problem that lstat has.
* modules/canonicalize-lgpl (Depends-on): Remove lstat, sys_stat.
---
 ChangeLog                 |  8 +++++++
 lib/canonicalize-lgpl.c   | 49 ++++++++++++++-------------------------
 modules/canonicalize-lgpl |  2 --
 3 files changed, 26 insertions(+), 33 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index cbe4558d5..27afc2b4a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2020-12-02  Paul Eggert  <eggert@cs.ucla.edu>
+
+       canonicalize-lgpl: fix EOVERFLOW bug
+       * lib/canonicalize-lgpl.c: Do not include <sys/stat.h>.
+       (__realpath): Do not use lstat.  Just use readlink, as this
+       suffices and it avoids the EOVERFLOW problem that lstat has.
+       * modules/canonicalize-lgpl (Depends-on): Remove lstat, sys_stat.
+
 2020-12-02  Bruno Haible  <bruno@clisp.org>
 
        strsignal-tests: Fix test failure on macOS 10.13.
diff --git a/lib/canonicalize-lgpl.c b/lib/canonicalize-lgpl.c
index edac98f83..981300aa7 100644
--- a/lib/canonicalize-lgpl.c
+++ b/lib/canonicalize-lgpl.c
@@ -36,7 +36,6 @@
 #if HAVE_SYS_PARAM_H || defined _LIBC
 # include <sys/param.h>
 #endif
-#include <sys/stat.h>
 #include <errno.h>
 #include <stddef.h>
 
@@ -198,12 +197,6 @@ __realpath (const char *name, char *resolved)
 
   for (end = start; *start; start = end)
     {
-#ifdef _LIBC
-      struct stat64 st;
-#else
-      struct stat st;
-#endif
-
       /* Skip sequence of multiple path-separators.  */
       while (ISSLASH (*start))
         ++start;
@@ -212,9 +205,7 @@ __realpath (const char *name, char *resolved)
       for (end = start; *end && !ISSLASH (*end); ++end)
         /* Nothing.  */;
 
-      if (end - start == 0)
-        break;
-      else if (end - start == 1 && start[0] == '.')
+      if (end - start == 1 && start[0] == '.')
         /* nothing */;
       else if (end - start == 2 && start[0] == '.' && start[1] == '.')
         {
@@ -272,20 +263,17 @@ __realpath (const char *name, char *resolved)
 #endif
           *dest = '\0';
 
-          /* FIXME: if lstat fails with errno == EOVERFLOW,
-             the entry exists.  */
-#ifdef _LIBC
-          if (__lxstat64 (_STAT_VER, rpath, &st) < 0)
-#else
-          if (lstat (rpath, &st) < 0)
-#endif
-            goto error;
-
-          if (S_ISLNK (st.st_mode))
+          char linkbuf[128];
+          ssize_t n = __readlink (rpath, linkbuf, sizeof linkbuf);
+          if (n < 0)
+            {
+              if (errno != EINVAL)
+                goto error;
+            }
+          else
             {
               char *buf;
               size_t len;
-              ssize_t n;
 
               if (++num_links > MAXSYMLINKS)
                 {
@@ -302,11 +290,15 @@ __realpath (const char *name, char *resolved)
                       goto error;
                     }
                 }
-              buf = extra_buf + path_max;
-
-              n = __readlink (rpath, buf, path_max - 1);
-              if (n < 0)
-                goto error;
+              if (n < sizeof linkbuf)
+                buf = linkbuf;
+              else
+                {
+                  buf = extra_buf + path_max;
+                  n = __readlink (rpath, buf, path_max - 1);
+                  if (n < 0)
+                    goto error;
+                }
               buf[n] = '\0';
 
               len = strlen (end);
@@ -350,11 +342,6 @@ __realpath (const char *name, char *resolved)
                     dest++;
                 }
             }
-          else if (!S_ISDIR (st.st_mode) && *end != '\0')
-            {
-              __set_errno (ENOTDIR);
-              goto error;
-            }
         }
     }
   if (dest > rpath + prefix_len + 1 && ISSLASH (dest[-1]))
diff --git a/modules/canonicalize-lgpl b/modules/canonicalize-lgpl
index 20ee7908b..701b492db 100644
--- a/modules/canonicalize-lgpl
+++ b/modules/canonicalize-lgpl
@@ -14,12 +14,10 @@ alloca-opt        [test $HAVE_CANONICALIZE_FILE_NAME = 0 || 
test $REPLACE_CANONI
 double-slash-root [test $HAVE_CANONICALIZE_FILE_NAME = 0 || test 
$REPLACE_CANONICALIZE_FILE_NAME = 1]
 errno             [test $HAVE_CANONICALIZE_FILE_NAME = 0 || test 
$REPLACE_CANONICALIZE_FILE_NAME = 1]
 filename          [test $HAVE_CANONICALIZE_FILE_NAME = 0 || test 
$REPLACE_CANONICALIZE_FILE_NAME = 1]
-lstat             [test $HAVE_CANONICALIZE_FILE_NAME = 0 || test 
$REPLACE_CANONICALIZE_FILE_NAME = 1]
 malloca           [test $HAVE_CANONICALIZE_FILE_NAME = 0 || test 
$REPLACE_CANONICALIZE_FILE_NAME = 1]
 memmove           [test $HAVE_CANONICALIZE_FILE_NAME = 0 || test 
$REPLACE_CANONICALIZE_FILE_NAME = 1]
 pathmax           [test $HAVE_CANONICALIZE_FILE_NAME = 0 || test 
$REPLACE_CANONICALIZE_FILE_NAME = 1]
 readlink          [test $HAVE_CANONICALIZE_FILE_NAME = 0 || test 
$REPLACE_CANONICALIZE_FILE_NAME = 1]
-sys_stat          [test $HAVE_CANONICALIZE_FILE_NAME = 0 || test 
$REPLACE_CANONICALIZE_FILE_NAME = 1]
 
 configure.ac:
 gl_CANONICALIZE_LGPL
-- 
2.27.0