aio: negative offset should return -EINVAL

An AIO read or write should return -EINVAL if the offset is negative.
This check matches the one in pread and pwrite.

This was found by the libaio test suite.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Zach Brown <zach.brown@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/aio.c

@@ -1329,6 +1329,10 @@ static ssize_t aio_rw_vect_retry(struct kiocb *iocb)
 		opcode = IOCB_CMD_PWRITEV;
 	}
 
+	/* This matches the pread()/pwrite() logic */
+	if (iocb->ki_pos < 0)
+		return -EINVAL;
+
 	do {
 		ret = rw_op(iocb, &iocb->ki_iovec[iocb->ki_cur_seg],
 			    iocb->ki_nr_segs - iocb->ki_cur_seg,