Re: [PATCH v4 11/16] rpmsg: virtio: register the rpmsg_ctrl device

From: Dan Carpenter
Date: Thu Feb 18 2021 - 09:15:00 EST

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In reply to: Arnaud Pouliquen: "[PATCH v4 11/16] rpmsg: virtio: register the rpmsg_ctrl device"
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Hi Arnaud,

url: https://github.com/0day-ci/linux/commits/Arnaud-Pouliquen/introduce-a-generic-IOCTL-interface-for-RPMsg-channels-management/20210217-214044
base: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git f40ddce88593482919761f74910f42f4b84c004b
config: x86_64-randconfig-m001-20210215 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-15) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@xxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>

smatch warnings:
drivers/rpmsg/virtio_rpmsg_bus.c:977 rpmsg_probe() error: uninitialized symbol 'vch'.

vim +/vch +977 drivers/rpmsg/virtio_rpmsg_bus.c

bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 845 static int rpmsg_probe(struct virtio_device *vdev)
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 846 {
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 847 vq_callback_t *vq_cbs[] = { rpmsg_recv_done, rpmsg_xmit_done };
f7ad26ff952b3c Stefan Hajnoczi 2015-12-17 848 static const char * const names[] = { "input", "output" };
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 849 struct virtqueue *vqs[2];
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 850 struct virtproc_info *vrp;
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 851 struct virtio_rpmsg_channel *vch;
e3bba4363fe87b Arnaud Pouliquen 2021-02-17 852 struct rpmsg_device *rpdev_ns = NULL, *rpdev_ctrl = NULL;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 853 void *bufs_va;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 854 int err = 0, i;
b1b9891441fa33 Suman Anna 2014-09-16 855 size_t total_buf_space;
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 856 bool notify;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 857
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 858 vrp = kzalloc(sizeof(*vrp), GFP_KERNEL);

You might want to consider updating this stuff to devm_kzalloc() which
is trendy with the kids these days. It's cleaned up automatically when
the module is released.

bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 859 if (!vrp)
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 860 return -ENOMEM;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 861
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 862 vrp->vdev = vdev;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 863
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 864 idr_init(&vrp->endpoints);
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 865 mutex_init(&vrp->endpoints_lock);
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 866 mutex_init(&vrp->tx_lock);
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 867 init_waitqueue_head(&vrp->sendq);
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 868
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 869 /* We expect two virtqueues, rx and tx (and in this order) */
9b2bbdb2275884 Michael S. Tsirkin 2017-03-06 870 err = virtio_find_vqs(vdev, 2, vqs, vq_cbs, names, NULL);
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 871 if (err)
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 872 goto free_vrp;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 873
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 874 vrp->rvq = vqs[0];
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 875 vrp->svq = vqs[1];
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 876
b1b9891441fa33 Suman Anna 2014-09-16 877 /* we expect symmetric tx/rx vrings */
b1b9891441fa33 Suman Anna 2014-09-16 878 WARN_ON(virtqueue_get_vring_size(vrp->rvq) !=
b1b9891441fa33 Suman Anna 2014-09-16 879 virtqueue_get_vring_size(vrp->svq));
b1b9891441fa33 Suman Anna 2014-09-16 880
b1b9891441fa33 Suman Anna 2014-09-16 881 /* we need less buffers if vrings are small */
b1b9891441fa33 Suman Anna 2014-09-16 882 if (virtqueue_get_vring_size(vrp->rvq) < MAX_RPMSG_NUM_BUFS / 2)
b1b9891441fa33 Suman Anna 2014-09-16 883 vrp->num_bufs = virtqueue_get_vring_size(vrp->rvq) * 2;
b1b9891441fa33 Suman Anna 2014-09-16 884 else
b1b9891441fa33 Suman Anna 2014-09-16 885 vrp->num_bufs = MAX_RPMSG_NUM_BUFS;
b1b9891441fa33 Suman Anna 2014-09-16 886
f93848f9eeb0f8 Loic Pallardy 2017-03-28 887 vrp->buf_size = MAX_RPMSG_BUF_SIZE;
f93848f9eeb0f8 Loic Pallardy 2017-03-28 888
f93848f9eeb0f8 Loic Pallardy 2017-03-28 889 total_buf_space = vrp->num_bufs * vrp->buf_size;
b1b9891441fa33 Suman Anna 2014-09-16 890
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 891 /* allocate coherent memory for the buffers */
d999b622fcfb39 Loic Pallardy 2019-01-10 892 bufs_va = dma_alloc_coherent(vdev->dev.parent,
b1b9891441fa33 Suman Anna 2014-09-16 893 total_buf_space, &vrp->bufs_dma,
b1b9891441fa33 Suman Anna 2014-09-16 894 GFP_KERNEL);
3119b487e03650 Wei Yongjun 2013-04-29 895 if (!bufs_va) {
3119b487e03650 Wei Yongjun 2013-04-29 896 err = -ENOMEM;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 897 goto vqs_del;
3119b487e03650 Wei Yongjun 2013-04-29 898 }
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 899
de4064af76537f Suman Anna 2018-10-23 900 dev_dbg(&vdev->dev, "buffers: va %pK, dma %pad\n",
8d95b322ba34b1 Anna, Suman 2016-08-12 901 bufs_va, &vrp->bufs_dma);
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 902
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 903 /* half of the buffers is dedicated for RX */
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 904 vrp->rbufs = bufs_va;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 905
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 906 /* and half is dedicated for TX */
b1b9891441fa33 Suman Anna 2014-09-16 907 vrp->sbufs = bufs_va + total_buf_space / 2;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 908
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 909 /* set up the receive buffers */
b1b9891441fa33 Suman Anna 2014-09-16 910 for (i = 0; i < vrp->num_bufs / 2; i++) {
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 911 struct scatterlist sg;
f93848f9eeb0f8 Loic Pallardy 2017-03-28 912 void *cpu_addr = vrp->rbufs + i * vrp->buf_size;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 913
9dd87c2af651b0 Loic Pallardy 2017-03-28 914 rpmsg_sg_init(&sg, cpu_addr, vrp->buf_size);
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 915
cee51d69a45b6c Rusty Russell 2013-03-20 916 err = virtqueue_add_inbuf(vrp->rvq, &sg, 1, cpu_addr,
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 917 GFP_KERNEL);
57e1a37347d31c Rusty Russell 2012-10-16 918 WARN_ON(err); /* sanity check; this can't really happen */
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 919 }
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 920
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 921 /* suppress "tx-complete" interrupts */
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 922 virtqueue_disable_cb(vrp->svq);
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 923
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 924 vdev->priv = vrp;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 925
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 926 /* if supported by the remote processor, enable the name service */
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 927 if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_NS)) {
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 928 vch = kzalloc(sizeof(*vch), GFP_KERNEL);
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 929 if (!vch) {
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 930 err = -ENOMEM;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 931 goto free_coherent;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 932 }
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 933
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 934 /* Link the channel to our vrp */
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 935 vch->vrp = vrp;
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 936
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 937 /* Assign public information to the rpmsg_device */
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 938 rpdev_ns = &vch->rpdev;
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 939 rpdev_ns->ops = &virtio_rpmsg_ops;
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 940 rpdev_ns->little_endian = virtio_is_little_endian(vrp->vdev);
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 941
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 942 rpdev_ns->dev.parent = &vrp->vdev->dev;
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 943 rpdev_ns->dev.release = virtio_rpmsg_release_device;
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 944
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 945 err = rpmsg_ns_register_device(rpdev_ns);
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 946 if (err)
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 947 goto free_coherent;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 948 }

"vch" not initialized on else path. Also keep in mind that "rpdev_ctrl"
is NULL at this point.

bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 949
e3bba4363fe87b Arnaud Pouliquen 2021-02-17 950 rpdev_ctrl = rpmsg_virtio_add_char_dev(vdev);
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

e3bba4363fe87b Arnaud Pouliquen 2021-02-17 951 if (IS_ERR(rpdev_ctrl)) {
e3bba4363fe87b Arnaud Pouliquen 2021-02-17 952 err = PTR_ERR(rpdev_ctrl);
e3bba4363fe87b Arnaud Pouliquen 2021-02-17 953 goto free_coherent;

I should create a Smatch warning for this as well.

e3bba4363fe87b Arnaud Pouliquen 2021-02-17 954 }
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 955 /*
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 956 * Prepare to kick but don't notify yet - we can't do this before
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 957 * device is ready.
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 958 */
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 959 notify = virtqueue_kick_prepare(vrp->rvq);
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 960
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 961 /* From this point on, we can notify and get callbacks. */
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 962 virtio_device_ready(vdev);
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 963
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 964 /* tell the remote processor it can start sending messages */
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 965 /*
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 966 * this might be concurrent with callbacks, but we are only
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 967 * doing notify, not a full kick here, so that's ok.
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 968 */
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 969 if (notify)
71e4b8bf0482fc Michael S. Tsirkin 2015-03-12 970 virtqueue_notify(vrp->rvq);
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 971
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 972 dev_info(&vdev->dev, "rpmsg host is online\n");
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 973
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 974 return 0;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 975
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 976 free_coherent:
950a7388f02bf7 Arnaud Pouliquen 2020-11-20 @977 kfree(vch);
^^^^^^^^^^
Uninitalized.

e3bba4363fe87b Arnaud Pouliquen 2021-02-17 978 kfree(to_virtio_rpmsg_channel(rpdev_ctrl));

Now, let's say that "rpdev_ctrl" is NULL. That's fine because
to_virtio_rpmsg_channel() is a no-op so it becomes kfree(NULL) which
is a no-op. But why even have the to_virtio_rpmsg_channel() function
if we are going to rely on it being a no-op?

If "rpdev_ctrl" is an error pointer this will crash. The problem is we
are freeing stuff that was not allocated. The fix for this is:

1) Free the most recent successful allocation.
2) The unwind code should mirror the allocation code.
3) Choose label names which say what the goto does. If the most recent
allocation was "vch" the goto should be "goto free_vch;"
4) Every allocation function should have a matching free function. It's
a layering violation to have to know that the internals of
rpmsg_virtio_add_char_dev().

So create function:

void rpmsg_virtio_del_char_dev(struct rpmsg_device *rpdev_ctrl)
{
if (!rpdev_ctrl)
return;
kfree(to_virtio_rpmsg_channel(rpdev_ctrl));
}

The clean up code looks like this:

return 0;

free_vch:
if (virtio_has_feature(vdev, VIRTIO_RPMSG_F_NS))
kfree(vch);
free_ctrl:
rpmsg_virtio_del_char_dev(rpdev_ctrl);
free_coherent:
dma_free_coherent(vdev->dev.parent, total_buf_space,
bufs_va, vrp->bufs_dma);
vqs_del:
vdev->config->del_vqs(vrp->vdev);

Then just go through the function and as you read down the code keep
track of the most recent successful allocation and goto the correct
free label.

d999b622fcfb39 Loic Pallardy 2019-01-10 979 dma_free_coherent(vdev->dev.parent, total_buf_space,
eeb0074f36d1ab Fernando Guzman Lugo 2012-08-29 980 bufs_va, vrp->bufs_dma);
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 981 vqs_del:
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 982 vdev->config->del_vqs(vrp->vdev);
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 983 free_vrp:
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 984 kfree(vrp);
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 985 return err;
bcabbccabffe73 Ohad Ben-Cohen 2011-10-20 986 }

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@xxxxxxxxxxxx

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Next message: Lennert Buytenhek: "[PATCH v3 2/2] io_uring: add support for IORING_OP_GETDENTS"
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In reply to: Arnaud Pouliquen: "[PATCH v4 11/16] rpmsg: virtio: register the rpmsg_ctrl device"
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