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

[Paolo Bonzini]

On 15/11/18 12:45, Marc-André Lureau wrote:
> 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
>>
>>
> 
> 

Queued, thanks.

Paolo