[PATCH v1 1/6] virtio console: Harden multiport against invalid host input

Alexander Shishkin
2023-01-20T04:36:34Z

From: Andi Kleen <ak@linux.intel.com>

It's possible for the host to set the multiport flag, but pass in
0 multiports, which results in:

BUG: KASAN: slab-out-of-bounds in init_vqs+0x244/0x6c0 drivers/char/virtio_console.c:1878
Write of size 8 at addr ffff888001cc24a0 by task swapper/1

CPU: 0 PID: 1 Comm: swapper Not tainted 5.15.0-rc1-140273-gaab0bb9fbaa1-dirty #588
Call Trace:
init_vqs+0x244/0x6c0 drivers/char/virtio_console.c:1878
virtcons_probe+0x1a3/0x5b0 drivers/char/virtio_console.c:2042
virtio_dev_probe+0x2b9/0x500 drivers/virtio/virtio.c:263
call_driver_probe drivers/base/dd.c:515
really_probe+0x1c9/0x5b0 drivers/base/dd.c:601
really_probe_debug drivers/base/dd.c:694
__driver_probe_device+0x10d/0x1f0 drivers/base/dd.c:754
driver_probe_device+0x68/0x150 drivers/base/dd.c:786
__driver_attach+0xca/0x200 drivers/base/dd.c:1145
bus_for_each_dev+0x108/0x190 drivers/base/bus.c:301
driver_attach+0x30/0x40 drivers/base/dd.c:1162
bus_add_driver+0x325/0x3c0 drivers/base/bus.c:618
driver_register+0xf3/0x1d0 drivers/base/driver.c:171
...

Add a suitable sanity check.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Amit Shah <amit@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/char/virtio_console.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index 6a821118d553..f4fd5fe7cd3a 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -1843,6 +1843,9 @@ static int init_vqs(struct ports_device *portdev)
int err;

nr_ports = portdev->max_nr_ports;
+ if (use_multiport(portdev) && nr_ports < 1)
+ return -EINVAL;
+
nr_queues = use_multiport(portdev) ? (nr_ports + 1) * 2 : 2;

vqs = kmalloc_array(nr_queues, sizeof(struct virtqueue *), GFP_KERNEL);
--
2.39.0