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Thu, 11 Nov 2021 18:35:32 -0800 (PST) Received: from localhost ([223.226.77.81]) by smtp.gmail.com with ESMTPSA id a8sm3347968pgh.84.2021.11.11.18.35.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 11 Nov 2021 18:35:31 -0800 (PST) Date: Fri, 12 Nov 2021 08:05:29 +0530 From: Viresh Kumar To: Vincent Whitchurch Cc: wsa@kernel.org, jie.deng@intel.com, conghui.chen@intel.com, mst@redhat.com, virtualization@lists.linux-foundation.org, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@axis.com Subject: Re: [PATCH v2 1/2] i2c: virtio: disable timeout handling Message-ID: <20211112023529.2nypmrnm6mufcpjt@vireshk-i7> References: <20211111160412.11980-1-vincent.whitchurch@axis.com> <20211111160412.11980-2-vincent.whitchurch@axis.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211111160412.11980-2-vincent.whitchurch@axis.com> User-Agent: NeoMutt/20180716-391-311a52 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11-11-21, 17:04, 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 > Signed-off-by: Vincent Whitchurch > --- > drivers/i2c/busses/i2c-virtio.c | 14 +++++--------- > 1 file changed, 5 insertions(+), 9 deletions(-) > > diff --git a/drivers/i2c/busses/i2c-virtio.c b/drivers/i2c/busses/i2c-virtio.c > index f10a603b13fb..7b2474e6876f 100644 > --- a/drivers/i2c/busses/i2c-virtio.c > +++ b/drivers/i2c/busses/i2c-virtio.c > @@ -106,11 +106,10 @@ static int virtio_i2c_prepare_reqs(struct virtqueue *vq, > > static int virtio_i2c_complete_reqs(struct virtqueue *vq, > struct virtio_i2c_req *reqs, > - struct i2c_msg *msgs, int num, > - bool timedout) > + struct i2c_msg *msgs, int num) > { > struct virtio_i2c_req *req; > - bool failed = timedout; > + bool failed = false; > unsigned int len; > int i, j = 0; > > @@ -132,7 +131,7 @@ static int virtio_i2c_complete_reqs(struct virtqueue *vq, > j++; > } > > - return timedout ? -ETIMEDOUT : j; > + return j; > } > > static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, > @@ -141,7 +140,6 @@ static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, > struct virtio_i2c *vi = i2c_get_adapdata(adap); > struct virtqueue *vq = vi->vq; > struct virtio_i2c_req *reqs; > - unsigned long time_left; > int count; > > reqs = kcalloc(num, sizeof(*reqs), GFP_KERNEL); > @@ -164,11 +162,9 @@ static int virtio_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, > reinit_completion(&vi->completion); > virtqueue_kick(vq); > > - time_left = wait_for_completion_timeout(&vi->completion, adap->timeout); > - if (!time_left) > - dev_err(&adap->dev, "virtio i2c backend timeout.\n"); > + wait_for_completion(&vi->completion); I thought we decided on making this in insanely high value instead ? -- viresh