From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1F30CA935; Fri, 15 Aug 2025 12:01:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755259266; cv=none; b=X01JkQ/YshlbJnGyjr3DBwrYLxsDx25wc+487zDSYxgJpXdIVrHxcYtBXCpnea7LiZvRiNFbjNVHgToL5NACG0aCfZzcJOfT2wKDAQsWaRLYpSgjkV+pwqwnE6dL8j11XW7EZ7d1mSZZXjMipT/7x9DvFltFlD0OLDrWqtNb0aM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755259266; c=relaxed/simple; bh=dXRcxOAtorbhC+j9x/ix2NWzVwiygbqH+TVgVVdI9dc=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=LpKZLBkXe7ZxgnwZBd7DVti/4mDCWo7+5EO4JYohN8yn72FYJLNbV7EYNwhTgfGwIplnicJE+EaLlA78mQb0SSo47KUcL2aU8QusRdLs6CRs5ebvUUsQCyHBQEuavc11qs2Xp5vfdbnUwQW8XMJxi4e/HpDo81AO4Ypmcl4/zu4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TduMfL/n; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TduMfL/n" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B0D5AC4CEEB; Fri, 15 Aug 2025 12:01:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1755259265; bh=dXRcxOAtorbhC+j9x/ix2NWzVwiygbqH+TVgVVdI9dc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=TduMfL/nzSbkpOOvqdX3oBp+NFTAFSi3zaRYqWOyKvmhKtVKGcsY353pdgMgUuLPu q/+qwrm3o6Dd9sMhHaGMETUSv0c/XF4vn0cKgfS+o2+vYr5I+dDLfJk/rABXIWoq4E tqSMsjgi09mhZJUZZ0KIN8vy2dLApBrpHdOMkKN7h+iYpJsFVQE5cwsqlt8VQc2Wh6 XOWCGqN8i6psXa385oOZnzA+8nRQuIbVHbcbUsHMUWDOfBwvNu16rd++4zpBA/zoYL dvvXbmAkUMkKdoZ9xr5LISWFkC1HQ546TIu3FAmYIhakhUuIzfiiMcXNM4qR8lEc2N LiPQzm68j6P0w== Date: Fri, 15 Aug 2025 13:00:59 +0100 From: Will Deacon To: "Michael S. Tsirkin" Cc: syzbot , davem@davemloft.net, edumazet@google.com, eperezma@redhat.com, horms@kernel.org, jasowang@redhat.com, kuba@kernel.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, sgarzare@redhat.com, stefanha@redhat.com, syzkaller-bugs@googlegroups.com, virtualization@lists.linux.dev, xuanzhuo@linux.alibaba.com Subject: Re: [syzbot] [kvm?] [net?] [virt?] WARNING in virtio_transport_send_pkt_info Message-ID: References: <20250812052645-mutt-send-email-mst@kernel.org> <689b1156.050a0220.7f033.011c.GAE@google.com> <20250812061425-mutt-send-email-mst@kernel.org> <20250815063140-mutt-send-email-mst@kernel.org> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250815063140-mutt-send-email-mst@kernel.org> On Fri, Aug 15, 2025 at 06:44:47AM -0400, Michael S. Tsirkin wrote: > On Fri, Aug 15, 2025 at 11:09:24AM +0100, Will Deacon wrote: > > On Tue, Aug 12, 2025 at 06:15:46AM -0400, Michael S. Tsirkin wrote: > > > On Tue, Aug 12, 2025 at 03:03:02AM -0700, syzbot wrote: > > > > Hello, > > > > > > > > syzbot has tested the proposed patch but the reproducer is still triggering an issue: > > > > WARNING in virtio_transport_send_pkt_info > > > > > > OK so the issue triggers on > > > commit 6693731487a8145a9b039bc983d77edc47693855 > > > Author: Will Deacon > > > Date: Thu Jul 17 10:01:16 2025 +0100 > > > > > > vsock/virtio: Allocate nonlinear SKBs for handling large transmit buffers > > > > > > > > > but does not trigger on: > > > > > > commit 8ca76151d2c8219edea82f1925a2a25907ff6a9d > > > Author: Will Deacon > > > Date: Thu Jul 17 10:01:15 2025 +0100 > > > > > > vsock/virtio: Rename virtio_vsock_skb_rx_put() > > > > > > > > > > > > Will, I suspect your patch merely uncovers a latent bug > > > in zero copy handling elsewhere. I'm still looking at this, but I'm not sure zero-copy is the right place to focus on. The bisected patch 6693731487a8 ("vsock/virtio: Allocate nonlinear SKBs for handling large transmit buffers") only has two hunks. The first is for the non-zcopy case and the latter is a no-op for zcopy, as skb_len == VIRTIO_VSOCK_SKB_HEADROOM and so we end up with a linear SKB regardless. I'll keep digging... Will