From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45283) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bReIZ-0007KO-ES for qemu-devel@nongnu.org; Mon, 25 Jul 2016 07:43:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bReIT-0001iR-Fa for qemu-devel@nongnu.org; Mon, 25 Jul 2016 07:43:50 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:16515) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bReIT-0001iH-6s for qemu-devel@nongnu.org; Mon, 25 Jul 2016 07:43:45 -0400 From: Shmulik Ladkani Date: Mon, 25 Jul 2016 14:43:35 +0300 Message-Id: <1469447015-2276-1-git-send-email-shmulik.ladkani@oracle.com> Subject: [Qemu-devel] [PATCH] util: Relax assertion in iov_copy() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" , qemu-devel@nongnu.org Cc: Paolo Bonzini , Dmitry Fleytman , Jason Wang , Shmulik Ladkani From: Shmulik Ladkani In cases where iov_copy() is passed with zero 'bytes' argument and a non-zero 'offset' argument, nothing gets copied - as expected. However since no copy iterations are performed, 'offset' is left unaltered, leading to the final assert(offset == 0) to fail. Relax the assertion: if j (number of dst elements assigned) is zero, no need to err. Only if j!=0 (some dst elements assigned) AND offset!=0 we should err. Signed-off-by: Shmulik Ladkani --- util/iov.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Flow that led to the assertion was: net_tx_pkt_rebuild_payload() iov_copy(... , pkt->payload_len) where pkt->payload_len was correctly calculated to be 0 (a packet carrying just ipv4 header, without any payload). An alternative is to place the below code, early in iov_copy(): if (!bytes) return 0; diff --git a/util/iov.c b/util/iov.c index 003fcce..17de52d 100644 --- a/util/iov.c +++ b/util/iov.c @@ -260,7 +260,7 @@ unsigned iov_copy(struct iovec *dst_iov, unsigned int dst_iov_cnt, bytes -= len; offset = 0; } - assert(offset == 0); + assert(j == 0 || offset == 0); return j; } -- 1.9.1