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 @@ -1344,9 +1344,9 @@ 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; @@ -1595,7 +1595,6 @@ 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)