[v5,5/5] linux: Use getdents64 on readdir64 compat implementation

Message ID 20230127172834.391311-6-adhemerval.zanella@linaro.org
State Superseded
Delegated to: Florian Weimer
Headers
Series Fix opendir regression on some FS |

Checks

Context Check Description
dj/TryBot-apply_patch success Patch applied to master at the time it was sent
dj/TryBot-32bit success Build for i686

Commit Message

Adhemerval Zanella Jan. 27, 2023, 5:28 p.m. UTC
  It uses a similar strategy from the non-LFS readdir that also
uses getdents64 internally and uses a translation buffer to return
the compat readdir64 entry.

It allows to remove __old_getdents64.

Checked on i686-linux-gnu.
---
 sysdeps/unix/sysv/linux/dirstream.h  | 13 +++-
 sysdeps/unix/sysv/linux/getdents64.c | 93 ----------------------------
 sysdeps/unix/sysv/linux/olddirent.h  |  2 -
 sysdeps/unix/sysv/linux/readdir64.c  | 50 +++++++++++----
 4 files changed, 50 insertions(+), 108 deletions(-)
  

Patch

diff --git a/sysdeps/unix/sysv/linux/dirstream.h b/sysdeps/unix/sysv/linux/dirstream.h
index 8f58a1c3a6..b03ece4590 100644
--- a/sysdeps/unix/sysv/linux/dirstream.h
+++ b/sysdeps/unix/sysv/linux/dirstream.h
@@ -24,6 +24,11 @@ 
 #include <libc-lock.h>
 #include <telldir.h>
 
+#include <shlib-compat.h>
+#if SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2)
+# include <olddirent.h>
+#endif
+
 /* Directory stream type.
 
    The miscellaneous Unix `readdir' implementations read directory data
@@ -44,7 +49,13 @@  struct __dirstream
     int errcode;		/* Delayed error code.  */
 
 #if !defined __OFF_T_MATCHES_OFF64_T || !defined __INO_T_MATCHES_INO64_T
-    struct dirent tdp;
+    union
+      {
+        struct dirent tdp;
+#if  SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2)
+        struct __old_dirent64 tdp64;
+#    endif
+      };
 #endif
 #if _DIRENT_OFFSET_TRANSLATION
     struct dirstream_loc_t locs; /* off64_t to long int map for telldir.  */
diff --git a/sysdeps/unix/sysv/linux/getdents64.c b/sysdeps/unix/sysv/linux/getdents64.c
index 01c3517deb..db299864ed 100644
--- a/sysdeps/unix/sysv/linux/getdents64.c
+++ b/sysdeps/unix/sysv/linux/getdents64.c
@@ -36,97 +36,4 @@  weak_alias (__getdents64, getdents64)
 
 #if _DIRENT_MATCHES_DIRENT64
 strong_alias (__getdents64, __getdents)
-#else
-# include <shlib-compat.h>
-
-# if SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2)
-#  include <olddirent.h>
-#  include <unistd.h>
-
-static ssize_t
-handle_overflow (int fd, __off64_t offset, ssize_t count)
-{
-  /* If this is the first entry in the buffer, we can report the
-     error.  */
-  if (offset == 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)
-{
-  /* 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");
-
-  ssize_t retval = INLINE_SYSCALL_CALL (getdents64, fd, buf, nbytes);
-  if (retval > 0)
-    {
-      /* This is the marker for the first entry.  Offset 0 is reserved
-	 for the first entry (see rewinddir).  Here, we use it as a
-	 marker for the first entry in the buffer.  We never actually
-	 seek to offset 0 because handle_overflow reports the error
-	 directly, so it does not matter that the offset is incorrect
-	 if entries have been read from the descriptor before (so that
-	 the descriptor is not actually at offset 0).  */
-      __off64_t previous_offset = 0;
-
-      char *p = buf;
-      char *end = buf + retval;
-      while (p < end)
-	{
-	  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, previous_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));
-
-	  p += reclen;
-	  previous_offset = offset;
-	}
-     }
-  return retval;
-}
-# endif /* SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2)  */
 #endif /* _DIRENT_MATCHES_DIRENT64  */
diff --git a/sysdeps/unix/sysv/linux/olddirent.h b/sysdeps/unix/sysv/linux/olddirent.h
index cde95e192e..2d682a6919 100644
--- a/sysdeps/unix/sysv/linux/olddirent.h
+++ b/sysdeps/unix/sysv/linux/olddirent.h
@@ -36,8 +36,6 @@  extern struct __old_dirent64 *__old_readdir64_unlocked (DIR *__dirp)
         attribute_hidden;
 extern int __old_readdir64_r (DIR *__dirp, struct __old_dirent64 *__entry,
 			  struct __old_dirent64 **__result);
-extern __ssize_t __old_getdents64 (int __fd, char *__buf, size_t __nbytes)
-	attribute_hidden;
 int __old_scandir64 (const char * __dir,
 		     struct __old_dirent64 *** __namelist,
 		     int (*__selector) (const struct __old_dirent64 *),
diff --git a/sysdeps/unix/sysv/linux/readdir64.c b/sysdeps/unix/sysv/linux/readdir64.c
index b901071aa7..88e42c5e90 100644
--- a/sysdeps/unix/sysv/linux/readdir64.c
+++ b/sysdeps/unix/sysv/linux/readdir64.c
@@ -102,21 +102,43 @@  versioned_symbol (libc, __readdir64, readdir64, GLIBC_2_2);
 # if SHLIB_COMPAT(libc, GLIBC_2_1, GLIBC_2_2)
 #  include <olddirent.h>
 
+/* Translate the DP64 entry to the old LFS one in the translation buffer
+   at dirstream DS.  Return true is the translation was possible or
+   false if either an internal fields can be represented in the non-LFS
+   entry or if the translation can not be resized.  */
+static bool
+dirstream_old_entry (struct __dirstream *ds, const struct dirent64 *dp64)
+{
+  /* Check for overflow.  */
+  if (!in_ino_t_range (dp64->d_ino))
+    return false;
+
+  /* And if name is too large.  */
+  if (dp64->d_reclen - offsetof (struct dirent64, d_name) > NAME_MAX)
+    return false;
+
+  ds->filepos = dp64->d_off;
+
+  ds->tdp64.d_off = dp64->d_off;
+  ds->tdp64.d_ino = dp64->d_ino;
+  ds->tdp64.d_reclen = dp64->d_reclen;
+  ds->tdp64.d_type = dp64->d_type;
+  memcpy (ds->tdp64.d_name, dp64->d_name,
+	  dp64->d_reclen - offsetof (struct dirent64, d_name));
+
+  return true;
+}
+
 attribute_compat_text_section
 struct __old_dirent64 *
 __old_readdir64_unlocked (DIR *dirp)
 {
-  struct __old_dirent64 *dp;
-  int saved_errno = errno;
+  const int saved_errno = errno;
 
   if (dirp->offset >= dirp->size)
     {
       /* We've emptied out our buffer.  Refill it.  */
-
-      size_t maxread = dirp->allocation;
-      ssize_t bytes;
-
-      bytes = __old_getdents64 (dirp->fd, dirp->data, maxread);
+      ssize_t bytes = __getdents64 (dirp->fd, dirp->data, dirp->allocation);
       if (bytes <= 0)
 	{
 	  /* Linux may fail with ENOENT on some file systems if the
@@ -127,17 +149,21 @@  __old_readdir64_unlocked (DIR *dirp)
 	    __set_errno (saved_errno);
 	  return NULL;
 	}
-      dirp->size = (size_t) bytes;
+      dirp->size = bytes;
 
       /* Reset the offset into the buffer.  */
       dirp->offset = 0;
     }
 
-  dp = (struct __old_dirent64 *) &dirp->data[dirp->offset];
-  dirp->offset += dp->d_reclen;
-  dirp->filepos = dp->d_off;
+  struct dirent64 *dp64 = (struct dirent64 *) &dirp->data[dirp->offset];
+  dirp->offset += dp64->d_reclen;
 
-  return dp;
+  /* Skip entries which might overflow d_ino or for memory allocation failure
+     in case of large file names.  */
+  if (dirstream_old_entry (dirp, dp64))
+    return &dirp->tdp64;
+
+  return NULL;
 }
 
 attribute_compat_text_section