Re: [PATCH v2 08/14] virtio-net: Fix duplex=... and speed=... error handling

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Apr 22, 2020 at 03:07:13PM +0200, Markus Armbruster wrote:
> virtio_net_device_realize() rejects invalid duplex and speed values.
> The error handling is broken:
> 
>     $ ../qemu/bld-sani/x86_64-softmmu/qemu-system-x86_64 -S -display none -monitor stdio
>     QEMU 4.2.93 monitor - type 'help' for more information
>     (qemu) device_add virtio-net,duplex=x
>     Error: 'duplex' must be 'half' or 'full'
>     (qemu) c
>     =================================================================
>     ==15654==ERROR: AddressSanitizer: heap-use-after-free on address 0x62e000014590 at pc 0x560b75c8dc13 bp 0x7fffdf1a6950 sp 0x7fffdf1a6940
>     READ of size 8 at 0x62e000014590 thread T0
> 	#0 0x560b75c8dc12 in object_dynamic_cast_assert /work/armbru/qemu/qom/object.c:826
> 	#1 0x560b74c38ac0 in virtio_vmstate_change /work/armbru/qemu/hw/virtio/virtio.c:3210
> 	#2 0x560b74d9765e in vm_state_notify /work/armbru/qemu/softmmu/vl.c:1271
> 	#3 0x560b7494ba72 in vm_prepare_start /work/armbru/qemu/cpus.c:2156
> 	#4 0x560b7494bacd in vm_start /work/armbru/qemu/cpus.c:2162
> 	#5 0x560b75a7d890 in qmp_cont /work/armbru/qemu/monitor/qmp-cmds.c:160
> 	#6 0x560b75a8d70a in hmp_cont /work/armbru/qemu/monitor/hmp-cmds.c:1043
> 	#7 0x560b75a799f2 in handle_hmp_command /work/armbru/qemu/monitor/hmp.c:1082
>     [...]
> 
>     0x62e000014590 is located 33168 bytes inside of 42288-byte region [0x62e00000c400,0x62e000016930)
>     freed by thread T1 here:
> 	#0 0x7feadd39491f in __interceptor_free (/lib64/libasan.so.5+0x10d91f)
> 	#1 0x7feadcebcd7c in g_free (/lib64/libglib-2.0.so.0+0x55d7c)
> 	#2 0x560b75c8fd40 in object_unref /work/armbru/qemu/qom/object.c:1128
> 	#3 0x560b7498a625 in memory_region_unref /work/armbru/qemu/memory.c:1762
> 	#4 0x560b74999fa4 in do_address_space_destroy /work/armbru/qemu/memory.c:2788
> 	#5 0x560b762362fc in call_rcu_thread /work/armbru/qemu/util/rcu.c:283
> 	#6 0x560b761c8884 in qemu_thread_start /work/armbru/qemu/util/qemu-thread-posix.c:519
> 	#7 0x7fead9be34bf in start_thread (/lib64/libpthread.so.0+0x84bf)
> 
>     previously allocated by thread T0 here:
> 	#0 0x7feadd394d18 in __interceptor_malloc (/lib64/libasan.so.5+0x10dd18)
> 	#1 0x7feadcebcc88 in g_malloc (/lib64/libglib-2.0.so.0+0x55c88)
> 	#2 0x560b75c8cf8a in object_new /work/armbru/qemu/qom/object.c:699
> 	#3 0x560b75010ad9 in qdev_device_add /work/armbru/qemu/qdev-monitor.c:654
> 	#4 0x560b750120c2 in qmp_device_add /work/armbru/qemu/qdev-monitor.c:805
> 	#5 0x560b75012c1b in hmp_device_add /work/armbru/qemu/qdev-monitor.c:905
>     [...]
>     ==15654==ABORTING
> 
> Cause: virtio_net_device_realize() neglects to bail out after setting
> the error.  Fix that.
> 
> Fixes: 9473939ed7addcaaeb8fde5c093918fb7fa0919c
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

Acked-by: Michael S. Tsirkin <mst@redhat.com>

Feel free to merge with the rest of the patchset.

> ---
>  hw/net/virtio-net.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
> index a46e3b37a7..b52ff4ab63 100644
> --- a/hw/net/virtio-net.c
> +++ b/hw/net/virtio-net.c
> @@ -2947,6 +2947,7 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
>              n->net_conf.duplex = DUPLEX_FULL;
>          } else {
>              error_setg(errp, "'duplex' must be 'half' or 'full'");
> +            return;
>          }
>          n->host_features |= (1ULL << VIRTIO_NET_F_SPEED_DUPLEX);
>      } else {
> @@ -2955,7 +2956,9 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
>  
>      if (n->net_conf.speed < SPEED_UNKNOWN) {
>          error_setg(errp, "'speed' must be between 0 and INT_MAX");
> -    } else if (n->net_conf.speed >= 0) {
> +        return;
> +    }
> +    if (n->net_conf.speed >= 0) {
>          n->host_features |= (1ULL << VIRTIO_NET_F_SPEED_DUPLEX);
>      }
>  
> -- 
> 2.21.1