PATCH: Check d_ino and d_off sizes before using getdents syscall

["H.J. Lu" <hongjiu dot lu at intel dot com>]

Hi,

We have

struct kernel_dirent
  {
    long int d_ino;
    __kernel_off_t d_off;
    unsigned short int d_reclen;
    char d_name[256];
  };

and

struct dirent
  {
#ifndef __USE_FILE_OFFSET64
    __ino_t d_ino;
    __off_t d_off;
#else
    __ino64_t d_ino;
    __off64_t d_off;
#endif
    unsigned short int d_reclen;
    unsigned char d_type;
    char d_name[256];		/* We must not include limits.h! */
  };


We can use the getdents system call only if kernel and user dirents have
the same d_ino and d_off sizes.  On x32, they are different.  This
patch adds a check.  Tested on Linux/ia32, Linux/x86-64 and Linux/x32.
OK to install?

Thanks.


H.J.

	* sysdeps/unix/sysv/linux/getdents.c (__GETDENTS): Use
	getdents system call only if kernel and user dirents have the
	same d_ino and d_off sizes.

diff --git a/sysdeps/unix/sysv/linux/getdents.c b/sysdeps/unix/sysv/linux/getdents.c
index eb9cfef..f31cf83 100644
--- a/sysdeps/unix/sysv/linux/getdents.c
+++ b/sysdeps/unix/sysv/linux/getdents.c
@@ -99,7 +99,13 @@ __GETDENTS (int fd, char *buf, size_t nbytes)
   ssize_t retval;
 
 #ifdef __ASSUME_GETDENTS32_D_TYPE
-  if (sizeof (DIRENT_TYPE) == sizeof (struct dirent))
+  /* Sizes of d_ino and d_off in kernel_dirent and dirent must be the
+     same.  */
+  if (sizeof (DIRENT_TYPE) == sizeof (struct dirent)
+      && (sizeof (((struct kernel_dirent *) 0)->d_ino)
+	  == sizeof (((struct dirent *) 0)->d_ino))
+      && (sizeof (((struct kernel_dirent *) 0)->d_off)
+	  == sizeof (((struct dirent *) 0)->d_off)))
     {
       retval = INLINE_SYSCALL (getdents, 3, fd, CHECK_N(buf, nbytes), nbytes);