Re: [PATCH v2 1/2] i2c: virtio: disable timeout handling

Viresh Kumar
2021-11-23T09:54:42Z

On 23-11-21, 10:52, Wolfram Sang wrote:
> On Thu, Nov 11, 2021 at 05:04:11PM +0100, Vincent Whitchurch wrote:
> > If a timeout is hit, it can result is incorrect data on the I2C bus
> > and/or memory corruptions in the guest since the device can still be
> > operating on the buffers it was given while the guest has freed them.
> >
> > Here is, for example, the start of a slub_debug splat which was
> > triggered on the next transfer after one transfer was forced to timeout
> > by setting a breakpoint in the backend (rust-vmm/vhost-device):
> >
> > BUG kmalloc-1k (Not tainted): Poison overwritten
> > First byte 0x1 instead of 0x6b
> > Allocated in virtio_i2c_xfer+0x65/0x35c age=350 cpu=0 pid=29
> > __kmalloc+0xc2/0x1c9
> > virtio_i2c_xfer+0x65/0x35c
> > __i2c_transfer+0x429/0x57d
> > i2c_transfer+0x115/0x134
> > i2cdev_ioctl_rdwr+0x16a/0x1de
> > i2cdev_ioctl+0x247/0x2ed
> > vfs_ioctl+0x21/0x30
> > sys_ioctl+0xb18/0xb41
> > Freed in virtio_i2c_xfer+0x32e/0x35c age=244 cpu=0 pid=29
> > kfree+0x1bd/0x1cc
> > virtio_i2c_xfer+0x32e/0x35c
> > __i2c_transfer+0x429/0x57d
> > i2c_transfer+0x115/0x134
> > i2cdev_ioctl_rdwr+0x16a/0x1de
> > i2cdev_ioctl+0x247/0x2ed
> > vfs_ioctl+0x21/0x30
> > sys_ioctl+0xb18/0xb41
> >
> > There is no simple fix for this (the driver would have to always create
> > bounce buffers and hold on to them until the device eventually returns
> > the buffers), so just disable the timeout support for now.
> >
> > Fixes: 3cfc88380413d20f ("i2c: virtio: add a virtio i2c frontend driver")
> > Acked-by: Jie Deng <jie.deng@intel.com>
> > Signed-off-by: Vincent Whitchurch <vincent.whitchurch@axis.com>
>
> Applied to for-current, thanks!
>

Thanks, I completely forgot replying to the last email from Vincent.

FWIW,

Reviewed-by: Viresh Kumar <viresh.kumar@linaro.org>

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viresh