[glibc/azanella/bz23960-dirent] linux: Set internal DIR filepos as off64_t (BZ #23960, BZ #24050)

[Adhemerval Zanella <azanella@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=9a0e9771e0807072d589cf5171b77044f07fa9b4

commit 9a0e9771e0807072d589cf5171b77044f07fa9b4
Author: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Date:   Mon Apr 13 18:09:20 2020 -0300

    linux: Set internal DIR filepos as off64_t (BZ #23960, BZ #24050)
    
    It allows to obtain the expected entry offset on telldir and set
    it correctly on seekdir on platforms where long int is smaller
    than off64_t.
    
    On such cases opendir creates a map entry between the DIR d_off
    offset and the returned long int (the telldir return value).
    seekdir will then set the correct offset from the internal list
    using the telldir as the list key.
    
    It also removes the overflow check on readdir and the returned value
    will be truncated by the non-LFS off_t size.  As Joseph has noted
    in BZ #23960 comment #22, d_off is an opaque value and since
    telldir/seekdir works regardless of the returned dirent d_off value.
    
    Finally it removes the requirement to check for overflow values on
    telldir (BZ #24050).
    
    Checked on x86_64-linux-gnu, i686-linux-gnu, powerpc-linux-gnu,
    and arm-linux-gnueabihf.

Diff:
---
 dirent/tst-seekdir.c                        |   8 ++
 sysdeps/unix/sysv/linux/Makefile            |   1 +
 sysdeps/unix/sysv/linux/alpha/bits/dirent.h |   3 +
 sysdeps/unix/sysv/linux/bits/dirent.h       |   4 +
 sysdeps/unix/sysv/linux/closedir.c          |   4 +
 sysdeps/unix/sysv/linux/dirstream.h         |   6 +-
 sysdeps/unix/sysv/linux/opendir.c           |   3 +
 sysdeps/unix/sysv/linux/readdir.c           |  11 ++-
 sysdeps/unix/sysv/linux/rewinddir.c         |   5 +
 sysdeps/unix/sysv/linux/seekdir.c           |  35 ++++++-
 sysdeps/unix/sysv/linux/telldir.c           |  35 +++++++
 sysdeps/unix/sysv/linux/telldir.h           |  65 +++++++++++++
 sysdeps/unix/sysv/linux/tst-opendir-nolfs.c | 146 ++++++++++++++++++++++++++++
 13 files changed, 319 insertions(+), 7 deletions(-)

diff --git a/dirent/tst-seekdir.c b/dirent/tst-seekdir.c
index dcdd699b09..187eda7584 100644
--- a/dirent/tst-seekdir.c
+++ b/dirent/tst-seekdir.c
@@ -41,6 +41,14 @@ do_test (void)
       if (i == 400)
 	break;
     }
+  if (i < 3)
+    {
+      /* Non-lfs opendir skips entries that can not be represented (for
+	 instance if d_off is not an offset but rather an internal filesystem
+	 representation.  For this case there is no point in continue the
+	 testcase.  */
+      return 77;
+    }
 
   printf ("going back past 4-th entry...\n");
 
diff --git a/sysdeps/unix/sysv/linux/Makefile b/sysdeps/unix/sysv/linux/Makefile
index f298878e8f..33708f910b 100644
--- a/sysdeps/unix/sysv/linux/Makefile
+++ b/sysdeps/unix/sysv/linux/Makefile
@@ -465,6 +465,7 @@ ifeq ($(subdir),dirent)
 sysdep_routines += getdirentries getdirentries64
 tests += \
   tst-getdents64 \
+  tst-opendir-nolfs \
   tst-readdir64-compat \
   # tests
 endif # $(subdir) == dirent
diff --git a/sysdeps/unix/sysv/linux/alpha/bits/dirent.h b/sysdeps/unix/sysv/linux/alpha/bits/dirent.h
index c8a0cfe93f..586d75586a 100644
--- a/sysdeps/unix/sysv/linux/alpha/bits/dirent.h
+++ b/sysdeps/unix/sysv/linux/alpha/bits/dirent.h
@@ -54,4 +54,7 @@ struct dirent64
 /* Inform libc code that these two types are effectively identical.  */
 #define _DIRENT_MATCHES_DIRENT64	1
 
+/* alpha 'long int' is enough to handle off64_t.  */
+#define _DIRENT_OFFSET_TRANSLATION	0
+
 #endif /* bits/dirent.h */
diff --git a/sysdeps/unix/sysv/linux/bits/dirent.h b/sysdeps/unix/sysv/linux/bits/dirent.h
index ab34d986ff..bb02dcb70a 100644
--- a/sysdeps/unix/sysv/linux/bits/dirent.h
+++ b/sysdeps/unix/sysv/linux/bits/dirent.h
@@ -57,3 +57,7 @@ struct dirent64
 #else
 # define _DIRENT_MATCHES_DIRENT64	0
 #endif
+
+/* The telldir function returns long int, which may not be large enough to
+   store off64_t values.  In this case, translation is required.  */
+#define _DIRENT_OFFSET_TRANSLATION (LONG_WIDTH < 64)
diff --git a/sysdeps/unix/sysv/linux/closedir.c b/sysdeps/unix/sysv/linux/closedir.c
index f1c2608642..9585a6ca3a 100644
--- a/sysdeps/unix/sysv/linux/closedir.c
+++ b/sysdeps/unix/sysv/linux/closedir.c
@@ -47,6 +47,10 @@ __closedir (DIR *dirp)
   __libc_lock_fini (dirp->lock);
 #endif
 
+#if _DIRENT_OFFSET_TRANSLATION
+  dirstream_loc_clear (&dirp->locs);
+#endif
+
   free ((void *) dirp);
 
   return __close_nocancel (fd);
diff --git a/sysdeps/unix/sysv/linux/dirstream.h b/sysdeps/unix/sysv/linux/dirstream.h
index adcf8234f1..8f58a1c3a6 100644
--- a/sysdeps/unix/sysv/linux/dirstream.h
+++ b/sysdeps/unix/sysv/linux/dirstream.h
@@ -22,6 +22,7 @@
 #include <sys/types.h>
 
 #include <libc-lock.h>
+#include <telldir.h>
 
 /* Directory stream type.
 
@@ -38,13 +39,16 @@ struct __dirstream
     size_t size;		/* Total valid data in the block.  */
     size_t offset;		/* Current offset into the block.  */
 
-    off_t filepos;		/* Position of next entry to read.  */
+    off64_t filepos;		/* Position of next entry to read.  */
 
     int errcode;		/* Delayed error code.  */
 
 #if !defined __OFF_T_MATCHES_OFF64_T || !defined __INO_T_MATCHES_INO64_T
     struct dirent tdp;
 #endif
+#if _DIRENT_OFFSET_TRANSLATION
+    struct dirstream_loc_t locs; /* off64_t to long int map for telldir.  */
+#endif
 
     /* Directory block.  We must make sure that this block starts
        at an address that is aligned adequately enough to store
diff --git a/sysdeps/unix/sysv/linux/opendir.c b/sysdeps/unix/sysv/linux/opendir.c
index 4336196a4d..3e2caabb9d 100644
--- a/sysdeps/unix/sysv/linux/opendir.c
+++ b/sysdeps/unix/sysv/linux/opendir.c
@@ -129,6 +129,9 @@ __alloc_dir (int fd, bool close_fd, int flags,
   dirp->offset = 0;
   dirp->filepos = 0;
   dirp->errcode = 0;
+#if _DIRENT_OFFSET_TRANSLATION
+  dirstream_loc_init (&dirp->locs);
+#endif
 
   return dirp;
 }
diff --git a/sysdeps/unix/sysv/linux/readdir.c b/sysdeps/unix/sysv/linux/readdir.c
index cd0ccaf33a..7a7f484c36 100644
--- a/sysdeps/unix/sysv/linux/readdir.c
+++ b/sysdeps/unix/sysv/linux/readdir.c
@@ -36,6 +36,15 @@ dirstream_entry (struct __dirstream *ds, const struct dirent64 *dp64)
   if (dp64->d_reclen - offsetof (struct dirent64, d_name) > NAME_MAX)
     return false;
 
+  /* telldir can not return an error, so preallocate the map if the entry can
+     not be packed directly.  */
+  if (telldir_need_dirstream (dp64->d_off))
+    {
+      dirstream_loc_add (&ds->locs, dp64->d_off);
+      if (dirstream_loc_has_failed (&ds->locs))
+	return false;
+    }
+
   ds->filepos = dp64->d_off;
 
   ds->tdp.d_off = dp64->d_off;
@@ -76,7 +85,7 @@ __readdir_unlocked (DIR *dirp)
 
  	  /* Reset the offset into the buffer.  */
 	  dirp->offset = 0;
- 	}
+	}
 
       struct dirent64 *dp64 = (struct dirent64 *) &dirp->data[dirp->offset];
       dirp->offset += dp64->d_reclen;
diff --git a/sysdeps/unix/sysv/linux/rewinddir.c b/sysdeps/unix/sysv/linux/rewinddir.c
index c0fb7aa765..1b158a584f 100644
--- a/sysdeps/unix/sysv/linux/rewinddir.c
+++ b/sysdeps/unix/sysv/linux/rewinddir.c
@@ -33,6 +33,11 @@ __rewinddir (DIR *dirp)
   dirp->offset = 0;
   dirp->size = 0;
   dirp->errcode = 0;
+
+#ifndef __LP64__
+  dirstream_loc_clear (&dirp->locs);
+#endif
+
 #if IS_IN (libc)
   __libc_lock_unlock (dirp->lock);
 #endif
diff --git a/sysdeps/unix/sysv/linux/seekdir.c b/sysdeps/unix/sysv/linux/seekdir.c
index 939ccc4447..30cce691a4 100644
--- a/sysdeps/unix/sysv/linux/seekdir.c
+++ b/sysdeps/unix/sysv/linux/seekdir.c
@@ -22,14 +22,39 @@
 #include <dirstream.h>
 
 /* Seek to position POS in DIRP.  */
-/* XXX should be __seekdir ? */
 void
 seekdir (DIR *dirp, long int pos)
 {
+  off64_t filepos;
+
   __libc_lock_lock (dirp->lock);
-  (void) __lseek (dirp->fd, pos, SEEK_SET);
-  dirp->size = 0;
-  dirp->offset = 0;
-  dirp->filepos = pos;
+
+#if _DIRENT_OFFSET_TRANSLATION
+  union dirstream_packed dsp = { .l = pos };
+  if (dsp.p.is_packed == 1)
+    filepos = dsp.p.info;
+  else
+    {
+      size_t index = dsp.p.info;
+
+      if (index >= dirstream_loc_size (&dirp->locs))
+	{
+	  __libc_lock_unlock (dirp->lock);
+	  return;
+	}
+      filepos = *dirstream_loc_at (&dirp->locs, index);
+    }
+#else
+  filepos = pos;
+#endif
+
+  if (dirp->filepos != filepos)
+    {
+      __lseek64 (dirp->fd, filepos, SEEK_SET);
+      dirp->filepos = filepos;
+      dirp->offset = 0;
+      dirp->size = 0;
+    }
+
   __libc_lock_unlock (dirp->lock);
 }
diff --git a/sysdeps/unix/sysv/linux/telldir.c b/sysdeps/unix/sysv/linux/telldir.c
index 1e5c129e9f..c3ef14f3da 100644
--- a/sysdeps/unix/sysv/linux/telldir.c
+++ b/sysdeps/unix/sysv/linux/telldir.c
@@ -15,9 +15,11 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
+#include <assert.h>
 #include <dirent.h>
 
 #include <dirstream.h>
+#include <telldir.h>
 
 /* Return the current position of DIRP.  */
 long int
@@ -26,7 +28,40 @@ telldir (DIR *dirp)
   long int ret;
 
   __libc_lock_lock (dirp->lock);
+
+#if _DIRENT_OFFSET_TRANSLATION
+  /* If the directory position fits in the packet structure, returns it.
+     Otherwise, check if the position is already been recorded in the
+     dynamic array.  If not, add the new record.  */
+
+  union dirstream_packed dsp;
+
+  if (!telldir_need_dirstream (dirp->filepos))
+    {
+      dsp.p.is_packed = 1;
+      dsp.p.info = dirp->filepos;
+    }
+  else
+    {
+      dsp.l = -1;
+
+      size_t i;
+      for (i = 0; i < dirstream_loc_size (&dirp->locs); i++)
+	if (*dirstream_loc_at (&dirp->locs, i) == dirp->filepos)
+	  break;
+      /* It should be pre-allocated on readdir.  */
+      assert (i != dirstream_loc_size (&dirp->locs));
+
+      dsp.p.is_packed = 0;
+      /* This assignment might overflow, however most likely ENOME would
+	 happen long before.  */
+      dsp.p.info = i;
+    }
+
+  ret = dsp.l;
+#else
   ret = dirp->filepos;
+#endif
   __libc_lock_unlock (dirp->lock);
 
   return ret;
diff --git a/sysdeps/unix/sysv/linux/telldir.h b/sysdeps/unix/sysv/linux/telldir.h
new file mode 100644
index 0000000000..758bcb0eb3
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/telldir.h
@@ -0,0 +1,65 @@
+/* Linux internal telldir definitions.
+   Copyright (C) 2023 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
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _TELLDIR_H
+#define _TELLDIR_H 1
+
+#if _DIRENT_OFFSET_TRANSLATION
+/* On platforms where 'long int' is smaller than 'off64_t' this is how the
+   returned value is encoded and returned by 'telldir'.  If the directory
+   offset can be enconded in 31 bits it is returned in the 'info' member
+   with 'is_packed' set to 1.
+
+   Otherwise, the 'info' member describes an index in a dynamic array at
+   'DIR' structure.  */
+
+union dirstream_packed
+{
+  long int l;
+  struct
+  {
+    unsigned long int is_packed:1;
+    unsigned long int info:31;
+  } p;
+};
+
+_Static_assert (sizeof (long int) == sizeof (union dirstream_packed),
+		"sizeof (long int) != sizeof (union dirstream_packed)");
+
+/* telldir maintains a list of offsets that describe the obtained diretory
+   position if it can fit this information in the returned 'dirstream_packed'
+   struct.  */
+
+# define DYNARRAY_STRUCT  dirstream_loc_t
+# define DYNARRAY_ELEMENT off64_t
+# define DYNARRAY_PREFIX  dirstream_loc_
+# include <malloc/dynarray-skeleton.c>
+
+static __always_inline bool
+telldir_need_dirstream (__off64_t d_off)
+{
+  return d_off >= 1UL << 31;
+}
+#else
+
+_Static_assert (sizeof (long int) == sizeof (off64_t),
+		"sizeof (long int) != sizeof (off64_t)");
+
+#endif /* __LP64__  */
+
+#endif /* _TELLDIR_H  */
diff --git a/sysdeps/unix/sysv/linux/tst-opendir-nolfs.c b/sysdeps/unix/sysv/linux/tst-opendir-nolfs.c
new file mode 100644
index 0000000000..52e18171a7
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/tst-opendir-nolfs.c
@@ -0,0 +1,146 @@
+/* Check multiple telldir and seekdir.
+   Copyright (C) 2023 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <dirent.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <support/check.h>
+#include <support/support.h>
+#include <support/temp_file.h>
+#include <support/xunistd.h>
+
+/* Some filesystems returns an arbitrary value for d_off direnty entry (ext4
+   for instance, where the value is an internal hash key).  The idea of create
+   a large number of file is to try trigger a overflow d_off value in a entry
+   to check if telldir/seekdir does work corretly in such case.  */
+static const char *dirname;
+/* The 2 extra files are '.' and '..'.  */
+static const size_t nfiles = (1<<14) + 2;
+
+static inline bool
+in_ino_t_range (ino64_t v)
+{
+  ino_t s = v;
+  return s == v;
+}
+
+static inline bool
+in_off_t_range (off64_t v)
+{
+  off_t s = v;
+  return s == v;
+}
+
+static void
+do_prepare (int argc, char *argv[])
+{
+  dirname = support_create_temp_directory ("tst-opendir-nolfs-");
+
+  for (size_t i = 0; i < nfiles - 2; i++)
+    {
+      int fd = create_temp_file_in_dir ("tempfile.", dirname, NULL);
+      TEST_VERIFY_EXIT (fd > 0);
+      close (fd);
+    }
+}
+#define PREPARE do_prepare
+
+static int
+do_test (void)
+{
+  DIR *dirp = opendir (dirname);
+  TEST_VERIFY_EXIT (dirp != NULL);
+
+  long int *tdirp = xmalloc (nfiles * sizeof (long int));
+  struct dirent **ddirp = xmalloc (nfiles * sizeof (struct dirent *));
+
+  /* For non-LFS, the entry is skipped if it can not be converted.  */
+  int count = 0;
+  for (; count < nfiles; count++)
+    {
+      tdirp[count] = telldir (dirp);
+      struct dirent *dp = readdir (dirp);
+      if (dp == NULL)
+	break;
+      ddirp[count] = xmalloc (dp->d_reclen);
+      memcpy (ddirp[count], dp, dp->d_reclen);
+    }
+
+  closedir (dirp);
+
+  /* Check against the getdents64 syscall.  */
+  int fd = xopen (dirname, O_RDONLY | O_DIRECTORY, 0);
+  int i = 0;
+  while (true)
+    {
+      struct
+      {
+	char buffer[1024];
+	struct dirent64 pad;
+      } data;
+
+      ssize_t ret = getdents64 (fd, &data.buffer, sizeof (data.buffer));
+      if (ret < 0)
+	FAIL_EXIT1 ("getdents64: %m");
+      if (ret == 0)
+	break;
+
+      char *current = data.buffer;
+      char *end = data.buffer + ret;
+      while (current != end)
+	{
+	  struct dirent64 entry;
+          memcpy (&entry, current, sizeof (entry));
+          /* Truncate overlong strings.  */
+          entry.d_name[sizeof (entry.d_name) - 1] = '\0';
+          TEST_VERIFY (strlen (entry.d_name) < sizeof (entry.d_name) - 1);
+
+	  if (in_ino_t_range (entry.d_ino) && in_off_t_range (entry.d_off))
+	    {
+	      TEST_COMPARE_STRING (entry.d_name, ddirp[i]->d_name);
+	      TEST_COMPARE (entry.d_ino, ddirp[i]->d_ino);
+	      TEST_COMPARE (entry.d_off, ddirp[i]->d_off);
+	      TEST_COMPARE (entry.d_type, ddirp[i]->d_type);
+
+	      /* Offset zero is reserved for the first entry.  */
+	      TEST_VERIFY (entry.d_off != 0);
+
+	      TEST_VERIFY_EXIT (entry.d_reclen <= end - current);
+	      i++;
+	    }
+
+	  current += entry.d_reclen;
+	}
+    }
+
+  /* direntries_read has been called more than once.  */
+  TEST_COMPARE (count, i);
+
+  free (tdirp);
+  for (int i = 0; i < count; i++)
+    free (ddirp[i]);
+  free (ddirp);
+
+  return 0;
+}
+
+#include <support/test-driver.c>