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[Qemu-devel] Re: [PATCH 14/15] virtio-serial: Handle scatter-gather buff
From: |
Juan Quintela |
Subject: |
[Qemu-devel] Re: [PATCH 14/15] virtio-serial: Handle scatter-gather buffers for control messages |
Date: |
Tue, 30 Mar 2010 15:44:21 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/23.1 (gnu/linux) |
Amit Shah <address@hidden> wrote:
> Current control messages are small enough to not be split into multiple
> buffers but we could run into such a situation in the future or a
> malicious guest could cause such a situation.
>
> So handle the entire iov request for control messages.
>
> Also ensure the size of the control request is >= what we expect
> otherwise we risk accessing memory that we don't own.
>
> Signed-off-by: Amit Shah <address@hidden>
> CC: Avi Kivity <address@hidden>
> Reported-by: Avi Kivity <address@hidden>
> ---
> hw/virtio-serial-bus.c | 34 +++++++++++++++++++++++++++++++---
> 1 files changed, 31 insertions(+), 3 deletions(-)
>
> diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c
> index bd1223e..3edfeca 100644
> vser = DO_UPCAST(VirtIOSerial, vdev, vdev);
>
> + len = 0;
> + buf = NULL;
> while (virtqueue_pop(vq, &elem)) {
> - handle_control_message(vser, elem.out_sg[0].iov_base);
> - virtqueue_push(vq, &elem, elem.out_sg[0].iov_len);
> + size_t cur_len, copied;
> +
> + cur_len = iov_size(elem.out_sg, elem.out_num);
> + /*
> + * Allocate a new buf only if we didn't have one previously or
> + * if the size of the buf differs
> + */
> + if (cur_len != len) {
> + if (len) {
> + qemu_free(buf);
> + }
> + buf = qemu_malloc(cur_len);
> + len = cur_len;
> + }
This can be simplified to only allocate the buffer if it is less no?
if (cur_len > len) {
if (len) {
qemu_free(buf);
}
buf = qemu_malloc(cur_len);
len = cur_len;
}
This way we can elliminate allocations, no?
Later, Juan.
- [Qemu-devel] [PATCH 06/15] virtio-serial: whitespace: match surrounding code, (continued)
- [Qemu-devel] [PATCH 06/15] virtio-serial: whitespace: match surrounding code, Amit Shah, 2010/03/24
- [Qemu-devel] [PATCH 07/15] virtio-serial: Remove redundant check for 0-sized write request, Amit Shah, 2010/03/24
- [Qemu-devel] [PATCH 08/15] virtio-serial: Update copyright year to 2010, Amit Shah, 2010/03/24
- [Qemu-devel] [PATCH 09/15] virtio-serial: Propagate errors in initialising ports / devices in guest, Amit Shah, 2010/03/24
- [Qemu-devel] [PATCH 10/15] virtio-serial: Add QMP events for failed port/device add, Amit Shah, 2010/03/24
- [Qemu-devel] [PATCH 11/15] virtio-serial: Send out guest data to ports only if port is opened, Amit Shah, 2010/03/24
- [Qemu-devel] [PATCH 12/15] iov: Introduce a new file for helpers around iovs, add iov_from_buf(), Amit Shah, 2010/03/24
- [Qemu-devel] [PATCH 13/15] iov: Add iov_to_buf and iov_size helpers, Amit Shah, 2010/03/24
- [Qemu-devel] [PATCH 14/15] virtio-serial: Handle scatter-gather buffers for control messages, Amit Shah, 2010/03/24
- [Qemu-devel] [PATCH 15/15] virtio-serial: Handle scatter/gather input from the guest, Amit Shah, 2010/03/24
- [Qemu-devel] Re: [PATCH 14/15] virtio-serial: Handle scatter-gather buffers for control messages,
Juan Quintela <=
- [Qemu-devel] Re: [PATCH 14/15] virtio-serial: Handle scatter-gather buffers for control messages, Amit Shah, 2010/03/30
- [Qemu-devel] Re: [PATCH 10/15] virtio-serial: Add QMP events for failed port/device add, Luiz Capitulino, 2010/03/24
- [Qemu-devel] Re: [PATCH 10/15] virtio-serial: Add QMP events for failed port/device add, Amit Shah, 2010/03/24
- [Qemu-devel] Re: [PATCH 10/15] virtio-serial: Add QMP events for failed port/device add, Luiz Capitulino, 2010/03/25
- Re: [Qemu-devel] Re: [PATCH 10/15] virtio-serial: Add QMP events for failed port/device add, Jamie Lokier, 2010/03/25
- Re: [Qemu-devel] Re: [PATCH 10/15] virtio-serial: Add QMP events for failed port/device add, Amit Shah, 2010/03/25
- Re: [Qemu-devel] Re: [PATCH 10/15] virtio-serial: Add QMP events for failed port/device add, Jamie Lokier, 2010/03/26
- Re: [Qemu-devel] Re: [PATCH 10/15] virtio-serial: Add QMP events for failed port/device add, Amit Shah, 2010/03/26
- Re: [Qemu-devel] Re: [PATCH 10/15] virtio-serial: Add QMP events for failed port/device add, Jamie Lokier, 2010/03/26
- Re: [Qemu-devel] Re: [PATCH 10/15] virtio-serial: Add QMP events for failed port/device add, Amit Shah, 2010/03/26