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    Subject[PATCH 5.15 233/247] vduse: Fix NULL pointer dereference on sysfs access
    Date
    From: Xie Yongji <xieyongji@bytedance.com>

    commit b27ee76c74dc831d6e092eaebc2dfc9c0beed1c9 upstream.

    The control device has no drvdata. So we will get a
    NULL pointer dereference when accessing control
    device's msg_timeout attribute via sysfs:

    [ 132.841881][ T3644] BUG: kernel NULL pointer dereference, address: 00000000000000f8
    [ 132.850619][ T3644] RIP: 0010:msg_timeout_show (drivers/vdpa/vdpa_user/vduse_dev.c:1271)
    [ 132.869447][ T3644] dev_attr_show (drivers/base/core.c:2094)
    [ 132.870215][ T3644] sysfs_kf_seq_show (fs/sysfs/file.c:59)
    [ 132.871164][ T3644] ? device_remove_bin_file (drivers/base/core.c:2088)
    [ 132.872082][ T3644] kernfs_seq_show (fs/kernfs/file.c:164)
    [ 132.872838][ T3644] seq_read_iter (fs/seq_file.c:230)
    [ 132.873578][ T3644] ? __vmalloc_area_node (mm/vmalloc.c:3041)
    [ 132.874532][ T3644] kernfs_fop_read_iter (fs/kernfs/file.c:238)
    [ 132.875513][ T3644] __kernel_read (fs/read_write.c:440 (discriminator 1))
    [ 132.876319][ T3644] kernel_read (fs/read_write.c:459)
    [ 132.877129][ T3644] kernel_read_file (fs/kernel_read_file.c:94)
    [ 132.877978][ T3644] kernel_read_file_from_fd (include/linux/file.h:45 fs/kernel_read_file.c:186)
    [ 132.879019][ T3644] __do_sys_finit_module (kernel/module.c:4207)
    [ 132.879930][ T3644] __ia32_sys_finit_module (kernel/module.c:4189)
    [ 132.880930][ T3644] do_int80_syscall_32 (arch/x86/entry/common.c:112 arch/x86/entry/common.c:132)
    [ 132.881847][ T3644] entry_INT80_compat (arch/x86/entry/entry_64_compat.S:419)

    To fix it, don't create the unneeded attribute for
    control device anymore.

    Fixes: c8a6153b6c59 ("vduse: Introduce VDUSE - vDPA Device in Userspace")
    Reported-by: kernel test robot <oliver.sang@intel.com>
    Cc: stable@vger.kernel.org
    Signed-off-by: Xie Yongji <xieyongji@bytedance.com>
    Message-Id: <20220426073656.229-1-xieyongji@bytedance.com>
    Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/vdpa/vdpa_user/vduse_dev.c | 7 +++----
    1 file changed, 3 insertions(+), 4 deletions(-)

    --- a/drivers/vdpa/vdpa_user/vduse_dev.c
    +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
    @@ -1336,9 +1336,9 @@ static int vduse_create_dev(struct vduse

    dev->minor = ret;
    dev->msg_timeout = VDUSE_MSG_DEFAULT_TIMEOUT;
    - dev->dev = device_create(vduse_class, NULL,
    - MKDEV(MAJOR(vduse_major), dev->minor),
    - dev, "%s", config->name);
    + dev->dev = device_create_with_groups(vduse_class, NULL,
    + MKDEV(MAJOR(vduse_major), dev->minor),
    + dev, vduse_dev_groups, "%s", config->name);
    if (IS_ERR(dev->dev)) {
    ret = PTR_ERR(dev->dev);
    goto err_dev;
    @@ -1585,7 +1585,6 @@ static int vduse_init(void)
    return PTR_ERR(vduse_class);

    vduse_class->devnode = vduse_devnode;
    - vduse_class->dev_groups = vduse_dev_groups;

    ret = alloc_chrdev_region(&vduse_major, 0, VDUSE_DEV_MAX, "vduse");
    if (ret)

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