Re: [PATCH] vhost-user-blk: fix invalid memory access

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

Hi Li,

On 4/17/20 12:17 PM, Li Feng wrote:
> when s->inflight is freed, vhost_dev_free_inflight may try to access
> s->inflight->addr, it will retrigger the following issue.
> 
> ==7309==ERROR: AddressSanitizer: heap-use-after-free on address 0x604001020d18 at pc 0x555555ce948a bp 0x7fffffffb170 sp 0x7fffffffb160
> READ of size 8 at 0x604001020d18 thread T0
>      #0 0x555555ce9489 in vhost_dev_free_inflight /root/smartx/qemu-el7/qemu-test/hw/virtio/vhost.c:1473
>      #1 0x555555cd86eb in virtio_reset /root/smartx/qemu-el7/qemu-test/hw/virtio/virtio.c:1214
>      #2 0x5555560d3eff in virtio_pci_reset hw/virtio/virtio-pci.c:1859
>      #3 0x555555f2ac53 in device_set_realized hw/core/qdev.c:893
>      #4 0x5555561d572c in property_set_bool qom/object.c:1925
>      #5 0x5555561de8de in object_property_set_qobject qom/qom-qobject.c:27
>      #6 0x5555561d99f4 in object_property_set_bool qom/object.c:1188
>      #7 0x555555e50ae7 in qdev_device_add /root/smartx/qemu-el7/qemu-test/qdev-monitor.c:626

Maybe cut <--

>      #8 0x555555e51213 in qmp_device_add /root/smartx/qemu-el7/qemu-test/qdev-monitor.c:806
>      #9 0x555555e8ff40 in hmp_device_add /root/smartx/qemu-el7/qemu-test/hmp.c:1951
>      #10 0x555555be889a in handle_hmp_command /root/smartx/qemu-el7/qemu-test/monitor.c:3404
>      #11 0x555555beac8b in monitor_command_cb /root/smartx/qemu-el7/qemu-test/monitor.c:4296
>      #12 0x555556433eb7 in readline_handle_byte util/readline.c:393
>      #13 0x555555be89ec in monitor_read /root/smartx/qemu-el7/qemu-test/monitor.c:4279
>      #14 0x5555563285cc in tcp_chr_read chardev/char-socket.c:470
>      #15 0x7ffff670b968 in g_main_context_dispatch (/lib64/libglib-2.0.so.0+0x4a968)
>      #16 0x55555640727c in glib_pollfds_poll util/main-loop.c:215
>      #17 0x55555640727c in os_host_main_loop_wait util/main-loop.c:238
>      #18 0x55555640727c in main_loop_wait util/main-loop.c:497
>      #19 0x555555b2d0bf in main_loop /root/smartx/qemu-el7/qemu-test/vl.c:2013
>      #20 0x555555b2d0bf in main /root/smartx/qemu-el7/qemu-test/vl.c:4776
>      #21 0x7fffdd2eb444 in __libc_start_main (/lib64/libc.so.6+0x22444)
>      #22 0x555555b3767a  (/root/smartx/qemu-el7/qemu-test/x86_64-softmmu/qemu-system-x86_64+0x5e367a)

-->.

> 
> 0x604001020d18 is located 8 bytes inside of 40-byte region [0x604001020d10,0x604001020d38)
> freed by thread T0 here:
>      #0 0x7ffff6f00508 in __interceptor_free (/lib64/libasan.so.4+0xde508)
>      #1 0x7ffff671107d in g_free (/lib64/libglib-2.0.so.0+0x5007d)
> 
> previously allocated by thread T0 here:
>      #0 0x7ffff6f00a88 in __interceptor_calloc (/lib64/libasan.so.4+0xdea88)
>      #1 0x7ffff6710fc5 in g_malloc0 (/lib64/libglib-2.0.so.0+0x4ffc5)
> 
> SUMMARY: AddressSanitizer: heap-use-after-free /root/smartx/qemu-el7/qemu-test/hw/virtio/vhost.c:1473 in vhost_dev_free_inflight
> Shadow bytes around the buggy address:
>    0x0c08801fc150: fa fa 00 00 00 00 04 fa fa fa fd fd fd fd fd fa
>    0x0c08801fc160: fa fa fd fd fd fd fd fd fa fa 00 00 00 00 04 fa
>    0x0c08801fc170: fa fa 00 00 00 00 00 01 fa fa 00 00 00 00 04 fa
>    0x0c08801fc180: fa fa 00 00 00 00 00 01 fa fa 00 00 00 00 00 01
>    0x0c08801fc190: fa fa 00 00 00 00 00 fa fa fa 00 00 00 00 04 fa
> =>0x0c08801fc1a0: fa fa fd[fd]fd fd fd fa fa fa fd fd fd fd fd fa
>    0x0c08801fc1b0: fa fa fd fd fd fd fd fa fa fa fd fd fd fd fd fa
>    0x0c08801fc1c0: fa fa 00 00 00 00 00 fa fa fa fd fd fd fd fd fd
>    0x0c08801fc1d0: fa fa 00 00 00 00 00 01 fa fa fd fd fd fd fd fa
>    0x0c08801fc1e0: fa fa fd fd fd fd fd fa fa fa fd fd fd fd fd fd
>    0x0c08801fc1f0: fa fa 00 00 00 00 00 01 fa fa fd fd fd fd fd fa
> Shadow byte legend (one shadow byte represents 8 application bytes):
>    Addressable:           00
>    Partially addressable: 01 02 03 04 05 06 07
>    Heap left redzone:       fa
>    Freed heap region:       fd

cut <--

>    Stack left redzone:      f1
>    Stack mid redzone:       f2
>    Stack right redzone:     f3
>    Stack after return:      f5
>    Stack use after scope:   f8
>    Global redzone:          f9
>    Global init order:       f6
>    Poisoned by user:        f7
>    Container overflow:      fc
>    Array cookie:            ac
>    Intra object redzone:    bb
>    ASan internal:           fe
>    Left alloca redzone:     ca
>    Right alloca redzone:    cb

-->

> ==7309==ABORTING
> 
> Signed-off-by: Li Feng <fengli@smartx.com>

What did you change since your previous version Raphael Norwitz already 
reviewed? The patch looks the same...
https://www.mail-archive.com/qemu-devel@nongnu.org/msg696385.html

> ---
>   hw/block/vhost-user-blk.c | 4 ++++
>   hw/virtio/vhost.c         | 2 +-
>   2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
> index 776b9af3eb..19e79b96e4 100644
> --- a/hw/block/vhost-user-blk.c
> +++ b/hw/block/vhost-user-blk.c
> @@ -463,7 +463,9 @@ reconnect:
>   
>   virtio_err:
>       g_free(s->vhost_vqs);
> +    s->vhost_vqs = NULL;
>       g_free(s->inflight);
> +    s->inflight = NULL;
>       for (i = 0; i < s->num_queues; i++) {
>           virtio_delete_queue(s->virtqs[i]);
>       }
> @@ -484,7 +486,9 @@ static void vhost_user_blk_device_unrealize(DeviceState *dev, Error **errp)
>       vhost_dev_cleanup(&s->dev);
>       vhost_dev_free_inflight(s->inflight);
>       g_free(s->vhost_vqs);
> +    s->vhost_vqs = NULL;
>       g_free(s->inflight);
> +    s->inflight = NULL;
>   
>       for (i = 0; i < s->num_queues; i++) {
>           virtio_delete_queue(s->virtqs[i]);
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 01ebe12f28..aff98a0ede 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -1514,7 +1514,7 @@ void vhost_dev_set_config_notifier(struct vhost_dev *hdev,
>   
>   void vhost_dev_free_inflight(struct vhost_inflight *inflight)
>   {
> -    if (inflight->addr) {
> +    if (inflight && inflight->addr) {
>           qemu_memfd_free(inflight->addr, inflight->size, inflight->fd);
>           inflight->addr = NULL;
>           inflight->fd = -1;
>