ext4: don't leave i_crtime.tv_sec uninitialized

If the i_crtime field is not present in the inode, don't leave the
field uninitialized.

Fixes: ef7f383 ("ext4: Add nanosecond timestamps")
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Tested-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org

fs/ext4/ext4.h

@@ -771,6 +771,8 @@ do {									       \
 	if (EXT4_FITS_IN_INODE(raw_inode, einode, xtime))		       \
 		(einode)->xtime.tv_sec = 				       \
 			(signed)le32_to_cpu((raw_inode)->xtime);	       \
+	else								       \
+		(einode)->xtime.tv_sec = 0;				       \
 	if (EXT4_FITS_IN_INODE(raw_inode, einode, xtime ## _extra))	       \
 		ext4_decode_extra_time(&(einode)->xtime,		       \
 				       raw_inode->xtime ## _extra);	       \