vhost: fix OOB access for invalid vhost ID

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
    Mellanox#1 0x1270f80 in rte_vhost_get_vhost_vring .../lib/vhost/vhost.c:951:8
    Mellanox#2 0x3ac95cb in eth_rxq_intr_disable
	.../drivers/net/vhost/rte_eth_vhost.c:647:8
    Mellanox#3 0x170e0bf in rte_eth_dev_rx_intr_disable
	.../lib/ethdev/rte_ethdev.c:5443:25
    Mellanox#4 0xf72ba7 in turn_on_off_intr .../examples/l3fwd-power/main.c:881:4
    Mellanox#5 0xf71045 in main_intr_loop .../examples/l3fwd-power/main.c:1061:6
    Mellanox#6 0x17f9292 in eal_thread_loop
	.../lib/eal/common/eal_common_thread.c:210:9
    Mellanox#7 0x18373f5 in eal_worker_thread_loop .../lib/eal/linux/eal.c:915:2
    Mellanox#8 0x7fddc16ae12c in start_thread (/lib64/libc.so.6+0x8b12c)
	(BuildId: 81daba31ee66dbd63efdc4252a872949d874d136)
    Mellanox#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)
    Mellanox#1 0x1836767 in eal_worker_thread_create .../lib/eal/linux/eal.c:952:6
    Mellanox#2 0x1834b83 in rte_eal_init .../lib/eal/linux/eal.c:1257:9
    Mellanox#3 0xf68902 in main .../examples/l3fwd-power/main.c:2496:8
    Mellanox#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.

Fixes: 4796ad6 ("examples/vhost: import userspace vhost application")
Cc: stable@dpdk.org

Signed-off-by: David Marchand <david.marchand@redhat.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

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 (likely(vid >= 0 && vid < RTE_MAX_VHOST_DEVICE))
+		dev = vhost_devices[vid];
 
 	if (unlikely(!dev)) {
 		VHOST_LOG_CONFIG("device", ERR, "(%d) device not found.\n", vid);