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([111.201.7.117]) by newxmesmtplogicsvrszc43-0.qq.com (NewEsmtp) with SMTP id E81C8F7; Thu, 04 Dec 2025 00:03:40 +0800 X-QQ-mid: xmsmtpt1764777820t4qo7i2do Message-ID: X-QQ-XMAILINFO: Mm3lGEhJcF5GES4dJXmrXXeRjVFRK9xLrz1OHc0rxpoLA+afC7a9iXoooZhjj4 toWUN1AVx0njlGItEE030M4WPQN5zD05g7mji1EtYEXqIvgYiceXGF7lBPga5KuJop7VY/csunpw n2LJ/6GtcJRCEpr823xHzkTC6Q5RgZC1XWtWOS6H0jtRkvL3ay52VuS+u4wJ1S435fLZVVv/7Mu/ cVhsURbGNz7iuExHYBBmYMG25EpCXsjX2UpzDnxXWEOLJTOtIEEULHxbFD+H7pu4fhzAoUop9GUH yDkzV3exGXX3+LiywTimz3dNggCqva4d87NBkzSVKBgWR8LP3n4SoOjBLEYU6omP1gYGBmyl0Kvz NLVhxD5q0/3u71Xezsrzc0XJXTvv+dtLfMayITb+kDdRQkr/fS8ZTHh8QqrG34Pcbae0IuyYwmpS 08HRuFluYAN2RXO0pBFXowJAU34Jil1EICUaAXnJwQi080+5duxZgAkamoW4WHevkyLr6rsSZSnL lc+SvJdMxm5DPavd5Pf2N6MoZX1zneLIggVimp2Gomd3CM+liSpm4muW8dkIwFe3u4e3B4ePg12A gE/6BZ96kh7bLL3UVSZwsIRDHg+RpQVcaijqYDUnK4bxwXxLPXhwWKS/YCscJnrG21XjLv4fIS8i EBA94xZpH6iX590So0Y8/Mnoj2GJAmNQ+b+z68xoheAu8OfCEA7daMTs/iQsEdeRtI3xtaUF1dBF aQmpYmLNBLFUqmeh1JOd5joAXAY+oJfOZqIN4lO/bFQtOotbtKa+gUYdm6HEg5okqsNs6IZflCSN Jq2E7ATchHPTHBPck3p//zYnyrK2cTommDsZ+jZq60vDXSxpaWTesZ04UouE5JNA5fjMfivzJo1a aGwIl6CAvj4v2Rz0MP0F97iZRP13Id7lZpkJg3CVlZlQLHpqWceqXuECwPiap7kKbWUeE8HSqdNu 53Uud1bGVJ0H7r3jI9zBhdEG7Nkvv3WmQrwMfJ+D8Ru1LJMeI/Xo65X7eiXSinrZSKl+tdfAazZ8 KPIbRkZQ== X-QQ-XMRINFO: OWPUhxQsoeAVDbp3OJHYyFg= From: Edward Adam Davis To: kuba@kernel.org Cc: davem@davemloft.net, eadavis@qq.com, edumazet@google.com, eperezma@redhat.com, horms@kernel.org, jasowang@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, mst@redhat.com, netdev@vger.kernel.org, pabeni@redhat.com, sgarzare@redhat.com, stefanha@redhat.com, syzbot+ci3edb9412aeb2e703@syzkaller.appspotmail.com, syzbot@lists.linux.dev, syzbot@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com, virtualization@lists.linux.dev, xuanzhuo@linux.alibaba.com Subject: [PATCH net-next V3] net: restore the iterator to its original state when an error occurs Date: Thu, 4 Dec 2025 00:03:39 +0800 X-OQ-MSGID: <20251203160339.303720-2-eadavis@qq.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In zerocopy_fill_skb_from_iter(), if two copy operations are performed and the first one succeeds while the second one fails, it returns a failure but the count in iterator has already been decremented due to the first successful copy. This ultimately affects the local variable rest_len in virtio_transport_send_pkt_info(), causing the remaining count in rest_len to be greater than the actual iterator count. As a result, packet sending operations continue even when the iterator count is zero, which further leads to skb->len being 0 and triggers the warning reported by syzbot [1]. Therefore, if the zerocopy operation fails, we should revert the iterator to its original state. The iov_iter_revert() in skb_zerocopy_iter_stream() is no longer needed and has been removed. [1] 'send_pkt()' returns 0, but 4096 expected WARNING: net/vmw_vsock/virtio_transport_common.c:430 at virtio_transport_se= nd_pkt_info+0xd1e/0xef0 net/vmw_vsock/virtio_transport_common.c:428, CPU#1:= syz.0.17/5986 Call Trace: virtio_transport_stream_enqueue net/vmw_vsock/virtio_transport_common.c:11= 13 [inline] virtio_transport_seqpacket_enqueue+0x143/0x1c0 net/vmw_vsock/virtio_transp= ort_common.c:841 vsock_connectible_sendmsg+0xabf/0x1040 net/vmw_vsock/af_vsock.c:2158 sock_sendmsg_nosec net/socket.c:727 [inline] __sock_sendmsg+0x21c/0x270 net/socket.c:746 Reported-by: syzbot+28e5f3d207b14bae122a@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=3D28e5f3d207b14bae122a Signed-off-by: Edward Adam Davis --- v3: - fix test tcp_zerocopy_maxfrags timeout v2: https://lore.kernel.org/all/tencent_BA768766163C533724966E36344AAE75470= 9@qq.com/ - Remove iov_iter_revert() in skb_zerocopy_iter_stream() v1: https://lore.kernel.org/all/tencent_387517772566B03DBD365896C036264AA80= 9@qq.com/ net/core/datagram.c | 9 ++++++++- net/core/skbuff.c | 1 - 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/net/core/datagram.c b/net/core/datagram.c index c285c6465923..3a612ebbbe80 100644 --- a/net/core/datagram.c +++ b/net/core/datagram.c @@ -748,9 +748,13 @@ int __zerocopy_sg_from_iter(struct msghdr *msg, struct= sock *sk, size_t length, struct net_devmem_dmabuf_binding *binding) { + struct iov_iter_state state; unsigned long orig_size =3D skb->truesize; unsigned long truesize; - int ret; + int ret, orig_len; + + iov_iter_save_state(from, &state); + orig_len =3D skb->len; =20 if (msg && msg->msg_ubuf && msg->sg_from_iter) ret =3D msg->sg_from_iter(skb, from, length); @@ -759,6 +763,9 @@ int __zerocopy_sg_from_iter(struct msghdr *msg, struct = sock *sk, else ret =3D zerocopy_fill_skb_from_iter(skb, from, length); =20 + if (ret =3D=3D -EFAULT || (ret =3D=3D -EMSGSIZE && skb->len =3D=3D orig_l= en)) + iov_iter_restore(from, &state); + truesize =3D skb->truesize - orig_size; if (sk && sk->sk_type =3D=3D SOCK_STREAM) { sk_wmem_queued_add(sk, truesize); diff --git a/net/core/skbuff.c b/net/core/skbuff.c index a00808f7be6a..7b8836f668b7 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -1908,7 +1908,6 @@ int skb_zerocopy_iter_stream(struct sock *sk, struct = sk_buff *skb, struct sock *save_sk =3D skb->sk; =20 /* Streams do not free skb on error. Reset to prev state. */ - iov_iter_revert(&msg->msg_iter, skb->len - orig_len); skb->sk =3D sk; ___pskb_trim(skb, orig_len); skb->sk =3D save_sk; --=20 2.43.0