glibc/old-getdents64.patch

2018-08-10  Florian Weimer  <fweimer@redhat.com>

	[BZ #23497]
	* sysdeps/unix/sysv/linux/getdents64.c (handle_overflow): New
	function.
	(__old_getdents64): Use getdents64.  Convert entries without
	moving them.
	* sysdeps/unix/sysv/linux/tst-readdir64-compat.c: New file.
	* sysdeps/unix/sysv/linux/Makefile (tests-internal): Add
	tst-readdir64-compat.

Index: glibc-2.28/sysdeps/unix/sysv/linux/Makefile
===================================================================
--- glibc-2.28.orig/sysdeps/unix/sysv/linux/Makefile
+++ glibc-2.28/sysdeps/unix/sysv/linux/Makefile
@@ -161,6 +161,7 @@ inhibit-glue = yes
 
 ifeq ($(subdir),dirent)
 sysdep_routines += getdirentries getdirentries64
+tests-internal += tst-readdir64-compat
 endif
 
 ifeq ($(subdir),nis)
Index: glibc-2.28/sysdeps/unix/sysv/linux/getdents64.c
===================================================================
--- glibc-2.28.orig/sysdeps/unix/sysv/linux/getdents64.c
+++ glibc-2.28/sysdeps/unix/sysv/linux/getdents64.c
@@ -33,41 +33,80 @@ strong_alias (__getdents64, __getdents)
 # include <shlib-compat.h>
 
 # if SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2)
-# include <olddirent.h>
+#  include <olddirent.h>
+#  include <unistd.h>
 
-/* kernel definition of as of 3.2.  */
-struct compat_linux_dirent
+static ssize_t
+handle_overflow (int fd, __off64_t offset, ssize_t count)
 {
-  /* Both d_ino and d_off are compat_ulong_t which are defined in all
-     architectures as 'u32'.  */
-  uint32_t        d_ino;
-  uint32_t        d_off;
-  unsigned short  d_reclen;
-  char            d_name[1];
-};
+  /* If this is the first entry in the buffer, we can report the
+     error.  */
+  if (count == 0)
+    {
+      __set_errno (EOVERFLOW);
+      return -1;
+    }
+
+  /* Otherwise, seek to the overflowing entry, so that the next call
+     will report the error, and return the data read so far..  */
+  if (__lseek64 (fd, offset, SEEK_SET) != 0)
+    return -1;
+  return count;
+}
 
 ssize_t
 __old_getdents64 (int fd, char *buf, size_t nbytes)
 {
-  ssize_t retval = INLINE_SYSCALL_CALL (getdents, fd, buf, nbytes);
+  /* We do not move the individual directory entries.  This is only
+     possible if the target type (struct __old_dirent64) is smaller
+     than the source type.  */
+  _Static_assert (offsetof (struct __old_dirent64, d_name)
+		  <= offsetof (struct dirent64, d_name),
+		  "__old_dirent64 is larger than dirent64");
+  _Static_assert (__alignof__ (struct __old_dirent64)
+		  <= __alignof__ (struct dirent64),
+		  "alignment of __old_dirent64 is larger than dirent64");
 
-  /* The kernel added the d_type value after the name.  Change this now.  */
-  if (retval != -1)
+  ssize_t retval = INLINE_SYSCALL_CALL (getdents64, fd, buf, nbytes);
+  if (retval > 0)
     {
-      union
-      {
-	struct compat_linux_dirent k;
-	struct dirent u;
-      } *kbuf = (void *) buf;
-
-      while ((char *) kbuf < buf + retval)
+      char *p = buf;
+      char *end = buf + retval;
+      while (p < end)
 	{
-	  char d_type = *((char *) kbuf + kbuf->k.d_reclen - 1);
-	  memmove (kbuf->u.d_name, kbuf->k.d_name,
-		   strlen (kbuf->k.d_name) + 1);
-	  kbuf->u.d_type = d_type;
+	  struct dirent64 *source = (struct dirent64 *) p;
+
+	  /* Copy out the fixed-size data.  */
+	  __ino_t ino = source->d_ino;
+	  __off64_t offset = source->d_off;
+	  unsigned int reclen = source->d_reclen;
+	  unsigned char type = source->d_type;
+
+	  /* Check for ino_t overflow.  */
+	  if (__glibc_unlikely (ino != source->d_ino))
+	    return handle_overflow (fd, offset, p - buf);
+
+	  /* Convert to the target layout.  Use a separate struct and
+	     memcpy to side-step aliasing issues.  */
+	  struct __old_dirent64 result;
+	  result.d_ino = ino;
+	  result.d_off = offset;
+	  result.d_reclen = reclen;
+	  result.d_type = type;
+
+	  /* Write the fixed-sized part of the result to the
+	     buffer.  */
+	  size_t result_name_offset = offsetof (struct __old_dirent64, d_name);
+	  memcpy (p, &result, result_name_offset);
+
+	  /* Adjust the position of the name if necessary.  Copy
+	     everything until the end of the record, including the
+	     terminating NUL byte.  */
+	  if (result_name_offset != offsetof (struct dirent64, d_name))
+	    memmove (p + result_name_offset, source->d_name,
+		     reclen - offsetof (struct dirent64, d_name));
 
-	  kbuf = (void *) ((char *) kbuf + kbuf->k.d_reclen);
+	  p += reclen;
 	}
      }
   return retval;
Index: glibc-2.28/sysdeps/unix/sysv/linux/tst-readdir64-compat.c
===================================================================
--- /dev/null
+++ glibc-2.28/sysdeps/unix/sysv/linux/tst-readdir64-compat.c
@@ -0,0 +1,111 @@
+/* Test readdir64 compatibility symbol.
+   Copyright (C) 2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library 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.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <dirent.h>
+#include <dlfcn.h>
+#include <errno.h>
+#include <shlib-compat.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+#include <support/check.h>
+
+/* Copied from <olddirent.h>.  */
+struct __old_dirent64
+  {
+    __ino_t d_ino;
+    __off64_t d_off;
+    unsigned short int d_reclen;
+    unsigned char d_type;
+    char d_name[256];
+  };
+
+typedef struct __old_dirent64 *(*compat_readdir64_type) (DIR *);
+
+#if TEST_COMPAT (libc, GLIBC_2_1, GLIBC_2_2)
+struct __old_dirent64 *compat_readdir64 (DIR *);
+compat_symbol_reference (libc, compat_readdir64, readdir64, GLIBC_2_1);
+#endif
+
+static int
+do_test (void)
+{
+#if TEST_COMPAT (libc, GLIBC_2_1, GLIBC_2_2)
+
+  /* Directory stream using the non-compat readdir64 symbol.  The test
+     checks against this.  */
+  DIR *dir_reference = opendir (".");
+  TEST_VERIFY_EXIT (dir_reference != NULL);
+  DIR *dir_test = opendir (".");
+  TEST_VERIFY_EXIT (dir_test != NULL);
+
+  /* This loop assumes that the enumeration order is consistent for
+     two different handles.  Nothing should write to the current
+     directory (in the source tree) while this test runs, so there
+     should not be any difference due to races.  */
+  size_t count = 0;
+  while (true)
+    {
+      errno = 0;
+      struct dirent64 *entry_reference = readdir64 (dir_reference);
+      if (entry_reference == NULL && errno != 0)
+        FAIL_EXIT1 ("readdir64 entry %zu: %m\n", count);
+      struct __old_dirent64 *entry_test = compat_readdir64 (dir_test);
+      if (entry_reference == NULL)
+        {
+          if (errno == EOVERFLOW)
+            {
+              TEST_VERIFY (entry_reference->d_ino
+                           != (__ino_t) entry_reference->d_ino);
+              printf ("info: inode number overflow at entry %zu\n", count);
+              break;
+            }
+          if (errno != 0)
+            FAIL_EXIT1 ("compat readdir64 entry %zu: %m\n", count);
+        }
+
+      /* Check that both streams end at the same time.  */
+      if (entry_reference == NULL)
+        {
+          TEST_VERIFY (entry_test == NULL);
+          break;
+        }
+      else
+        TEST_VERIFY_EXIT (entry_test != NULL);
+
+      /* Check that the entries are the same.  */
+      TEST_COMPARE_BLOB (entry_reference->d_name,
+                         strlen (entry_reference->d_name),
+                         entry_test->d_name, strlen (entry_test->d_name));
+      TEST_COMPARE (entry_reference->d_ino, entry_test->d_ino);
+      TEST_COMPARE (entry_reference->d_off, entry_test->d_off);
+      TEST_COMPARE (entry_reference->d_type, entry_test->d_type);
+      TEST_COMPARE (entry_reference->d_reclen, entry_test->d_reclen);
+
+      ++count;
+    }
+  printf ("info: %zu directory entries found\n", count);
+  TEST_VERIFY (count >= 3);     /* ".", "..", and some source files.  */
+
+  TEST_COMPARE (closedir (dir_test), 0);
+  TEST_COMPARE (closedir (dir_reference), 0);
+#endif
+  return 0;
+}
+
+#include <support/test-driver.c>