Re: [Qemu-devel] [PATCH] vhost-user-bridge: fix recvmsg iovlen

[Marc-André Lureau]

On Fri, Nov 9, 2018 at 9:39 PM Marc-André Lureau
<address@hidden> wrote:
>
> After iov_discard_front(), the iov may be smaller than its initial
> size. Fixes the heap-buffer-overflow spotted by ASAN:
>
> ==9036==ERROR: AddressSanitizer: heap-buffer-overflow on address 
> 0x6060000001e0 at pc 0x7fe632eca3f0 bp 0x7ffddc4a05a0 sp 0x7ffddc49fd48
> WRITE of size 32 at 0x6060000001e0 thread T0
>     #0 0x7fe632eca3ef  (/lib64/libasan.so.5+0x773ef)
>     #1 0x7fe632ecad23 in __interceptor_recvmsg (/lib64/libasan.so.5+0x77d23)
>     #2 0x561e7491936b in vubr_backend_recv_cb 
> /home/elmarco/src/qemu/tests/vhost-user-bridge.c:333
>     #3 0x561e74917711 in dispatcher_wait 
> /home/elmarco/src/qemu/tests/vhost-user-bridge.c:160
>     #4 0x561e7491c3b5 in vubr_run 
> /home/elmarco/src/qemu/tests/vhost-user-bridge.c:725
>     #5 0x561e7491c85c in main 
> /home/elmarco/src/qemu/tests/vhost-user-bridge.c:806
>     #6 0x7fe631a6c412 in __libc_start_main (/lib64/libc.so.6+0x24412)
>     #7 0x561e7491667d in _start 
> (/home/elmarco/src/qemu/build/tests/vhost-user-bridge+0x3967d)
>
> 0x6060000001e0 is located 0 bytes to the right of 64-byte region 
> [0x6060000001a0,0x6060000001e0)
> allocated by thread T0 here:
>     #0 0x7fe632f42848 in __interceptor_malloc (/lib64/libasan.so.5+0xef848)
>     #1 0x561e7493acd8 in virtqueue_alloc_element 
> /home/elmarco/src/qemu/contrib/libvhost-user/libvhost-user.c:1848
>     #2 0x561e7493c2a8 in vu_queue_pop 
> /home/elmarco/src/qemu/contrib/libvhost-user/libvhost-user.c:1954
>     #3 0x561e749189bf in vubr_backend_recv_cb 
> /home/elmarco/src/qemu/tests/vhost-user-bridge.c:297
>     #4 0x561e74917711 in dispatcher_wait 
> /home/elmarco/src/qemu/tests/vhost-user-bridge.c:160
>     #5 0x561e7491c3b5 in vubr_run 
> /home/elmarco/src/qemu/tests/vhost-user-bridge.c:725
>     #6 0x561e7491c85c in main 
> /home/elmarco/src/qemu/tests/vhost-user-bridge.c:806
>     #7 0x7fe631a6c412 in __libc_start_main (/lib64/libc.so.6+0x24412)
>
> SUMMARY: AddressSanitizer: heap-buffer-overflow (/lib64/libasan.so.5+0x773ef)
> Shadow bytes around the buggy address:
>   0x0c0c7fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>   0x0c0c7fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>   0x0c0c7fff8000: fa fa fa fa 00 00 00 00 00 00 05 fa fa fa fa fa
>   0x0c0c7fff8010: 00 00 00 00 00 00 00 00 fa fa fa fa fd fd fd fd
>   0x0c0c7fff8020: fd fd fd fd fa fa fa fa fd fd fd fd fd fd fd fd
> =>0x0c0c7fff8030: fa fa fa fa 00 00 00 00 00 00 00 00[fa]fa fa fa
>   0x0c0c7fff8040: fd fd fd fd fd fd fd fd fa fa fa fa fd fd fd fd
>   0x0c0c7fff8050: fd fd fd fd fa fa fa fa fd fd fd fd fd fd fd fd
>   0x0c0c7fff8060: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
>   0x0c0c7fff8070: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
>   0x0c0c7fff8080: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
>
> Signed-off-by: Marc-André Lureau <address@hidden>

ping

> ---
>  tests/vhost-user-bridge.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/tests/vhost-user-bridge.c b/tests/vhost-user-bridge.c
> index a07ce0f917..0033b61f2e 100644
> --- a/tests/vhost-user-bridge.c
> +++ b/tests/vhost-user-bridge.c
> @@ -323,7 +323,7 @@ vubr_backend_recv_cb(int sock, void *ctx)
>              .msg_name = (struct sockaddr *) &vubr->backend_udp_dest,
>              .msg_namelen = sizeof(struct sockaddr_in),
>              .msg_iov = sg,
> -            .msg_iovlen = elem->in_num,
> +            .msg_iovlen = num,
>              .msg_flags = MSG_DONTWAIT,
>          };
>          do {
> --
> 2.19.1.708.g4ede3d42df
>
>


-- 
Marc-André Lureau