Re: [PATCH] vhost: fix OOB access for invalid vid

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 2/27/23 11:59, David Marchand wrote:
> The net/vhost pmd currently provides a -1 vid when disabling interrupt
> after a virtio port got disconnected.
> 
> This can be caught when running with ASan.
> 
> First, start dpdk-l3fwd-power in interrupt mode with a net/vhost port.
> 
> $ ./build-clang/examples/dpdk-l3fwd-power -l0,1 --in-memory \
> 	-a 0000:00:00.0 \
> 	--vdev net_vhost0,iface=plop.sock,client=1\
> 	-- \
> 	-p 0x1 \
> 	--interrupt-only \
> 	--config '(0,0,1)' \
> 	--parse-ptype 0
> 
> Then start testpmd with virtio-user.
> 
> $ ./build-clang/app/dpdk-testpmd -l0,2 --single-file-segment --in-memory \
> 	-a 0000:00:00.0 \
> 	--vdev net_virtio_user0,path=plop.sock,server=1 \
> 	-- \
> 	-i
> 
> Finally stop testpmd.
> ASan then splats in dpdk-l3fwd-power:
> 
> =================================================================
> ==3641005==ERROR: AddressSanitizer: global-buffer-overflow on address
> 	0x000005ed0778 at pc 0x000001270f81 bp 0x7fddbd2eee20
> 	sp 0x7fddbd2eee18
> READ of size 8 at 0x000005ed0778 thread T2
>      #0 0x1270f80 in get_device .../lib/vhost/vhost.h:801:27
>      #1 0x1270f80 in rte_vhost_get_vhost_vring .../lib/vhost/vhost.c:951:8
>      #2 0x3ac95cb in eth_rxq_intr_disable
> 	.../drivers/net/vhost/rte_eth_vhost.c:647:8
>      #3 0x170e0bf in rte_eth_dev_rx_intr_disable
> 	.../lib/ethdev/rte_ethdev.c:5443:25
>      #4 0xf72ba7 in turn_on_off_intr .../examples/l3fwd-power/main.c:881:4
>      #5 0xf71045 in main_intr_loop .../examples/l3fwd-power/main.c:1061:6
>      #6 0x17f9292 in eal_thread_loop
> 	.../lib/eal/common/eal_common_thread.c:210:9
>      #7 0x18373f5 in eal_worker_thread_loop .../lib/eal/linux/eal.c:915:2
>      #8 0x7fddc16ae12c in start_thread (/lib64/libc.so.6+0x8b12c)
> 	(BuildId: 81daba31ee66dbd63efdc4252a872949d874d136)
>      #9 0x7fddc172fbbf in __GI___clone3 (/lib64/libc.so.6+0x10cbbf)
> 	(BuildId: 81daba31ee66dbd63efdc4252a872949d874d136)
> 
> 0x000005ed0778 is located 8 bytes to the left of global variable
> 	'vhost_devices' defined in '.../lib/vhost/vhost.c:24'
> 	(0x5ed0780) of size 8192
> 0x000005ed0778 is located 20 bytes to the right of global variable
> 	'vhost_config_log_level' defined in '.../lib/vhost/vhost.c:2174'
> 	(0x5ed0760) of size 4
> SUMMARY: AddressSanitizer: global-buffer-overflow
> 	.../lib/vhost/vhost.h:801:27 in get_device
> Shadow bytes around the buggy address:
>    0x000080bd2090: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
>    0x000080bd20a0: f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9 f9
>    0x000080bd20b0: f9 f9 f9 f9 00 f9 f9 f9 00 f9 f9 f9 00 f9 f9 f9
>    0x000080bd20c0: 00 00 00 00 00 00 00 f9 f9 f9 f9 f9 04 f9 f9 f9
>    0x000080bd20d0: 00 00 00 00 00 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
> =>0x000080bd20e0: 00 f9 f9 f9 f9 f9 f9 f9 04 f9 f9 f9 04 f9 f9[f9]
>    0x000080bd20f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>    0x000080bd2100: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>    0x000080bd2110: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>    0x000080bd2120: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>    0x000080bd2130: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 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
>    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
> Thread T2 created by T0 here:
>      #0 0xe98996 in __interceptor_pthread_create
> 	(.examples/dpdk-l3fwd-power+0xe98996)
> 	(BuildId: d0b984a3b0287b9e0f301b73426fa921aeecca3a)
>      #1 0x1836767 in eal_worker_thread_create .../lib/eal/linux/eal.c:952:6
>      #2 0x1834b83 in rte_eal_init .../lib/eal/linux/eal.c:1257:9
>      #3 0xf68902 in main .../examples/l3fwd-power/main.c:2496:8
>      #4 0x7fddc164a50f in __libc_start_call_main (/lib64/libc.so.6+0x2750f)
> 	(BuildId: 81daba31ee66dbd63efdc4252a872949d874d136)
> 
> ==3641005==ABORTING
> 
> More generally, any application passing an incorrect vid would trigger
> such an OOB access.
> 
> Cc: stable@dpdk.org
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>
> ---
> Note: even after this patch, reconnecting the virtio-user port with
> dpdk-l3fwd-power in interrupt mode still seems broken, as the net/vhost
> pmd keeps complaining about an issue with rx interrupt fds.
> 
> ---
>   lib/vhost/vhost.h | 5 ++++-
>   1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/vhost/vhost.h b/lib/vhost/vhost.h
> index 5750f0c005..d9e97280fa 100644
> --- a/lib/vhost/vhost.h
> +++ b/lib/vhost/vhost.h
> @@ -798,7 +798,10 @@ hva_to_gpa(struct virtio_net *dev, uint64_t vva, uint64_t len)
>   static __rte_always_inline struct virtio_net *
>   get_device(int vid)
>   {
> -	struct virtio_net *dev = vhost_devices[vid];
> +	struct virtio_net *dev = NULL;
> +
> +	if (vid >= 0 && vid < RTE_MAX_VHOST_DEVICE)

Maybe use likely() to help the compiler?

> +		dev = vhost_devices[vid];
>   
>   	if (unlikely(!dev)) {
>   		VHOST_LOG_CONFIG("device", ERR, "(%d) device not found.\n", vid);