Re: [PATCH v2] thermal/core: fix a UAF bug in __thermal_cooling_device_register()

From: Rafael J. Wysocki
Date: Fri Oct 15 2021 - 08:25:17 EST


On Fri, Oct 15, 2021 at 4:46 AM Ziyang Xuan
<william.xuanziyang@xxxxxxxxxx> wrote:
>
> When device_register() return failed, program will goto out_kfree_type
> to release 'cdev->device' by put_device(). That will call thermal_release()
> to free 'cdev'. But the follow-up processes access 'cdev' continually.
> That trggers the UAF bug.
>
> ====================================================================
> BUG: KASAN: use-after-free in __thermal_cooling_device_register+0x75b/0xa90
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
> Call Trace:
> dump_stack_lvl+0xe2/0x152
> print_address_description.constprop.0+0x21/0x140
> ? __thermal_cooling_device_register+0x75b/0xa90
> kasan_report.cold+0x7f/0x11b
> ? __thermal_cooling_device_register+0x75b/0xa90
> __thermal_cooling_device_register+0x75b/0xa90
> ? memset+0x20/0x40
> ? __sanitizer_cov_trace_pc+0x1d/0x50
> ? __devres_alloc_node+0x130/0x180
> devm_thermal_of_cooling_device_register+0x67/0xf0
> max6650_probe.cold+0x557/0x6aa
> ......
>
> Freed by task 258:
> kasan_save_stack+0x1b/0x40
> kasan_set_track+0x1c/0x30
> kasan_set_free_info+0x20/0x30
> __kasan_slab_free+0x109/0x140
> kfree+0x117/0x4c0
> thermal_release+0xa0/0x110
> device_release+0xa7/0x240
> kobject_put+0x1ce/0x540
> put_device+0x20/0x30
> __thermal_cooling_device_register+0x731/0xa90
> devm_thermal_of_cooling_device_register+0x67/0xf0
> max6650_probe.cold+0x557/0x6aa [max6650]
>
> Do not use 'cdev' again after put_device() to fix the problem like doing
> in thermal_zone_device_register().
>
> Fixes: 584837618100 ("thermal/drivers/core: Use a char pointer for the cooling device name")
> Signed-off-by: Ziyang Xuan <william.xuanziyang@xxxxxxxxxx>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> Reported-by: kernel test robot <lkp@xxxxxxxxx>
> ---
> drivers/thermal/thermal_core.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c
> index 97ef9b040b84..d2c196b298c1 100644
> --- a/drivers/thermal/thermal_core.c
> +++ b/drivers/thermal/thermal_core.c
> @@ -888,7 +888,7 @@ __thermal_cooling_device_register(struct device_node *np,
> {
> struct thermal_cooling_device *cdev;
> struct thermal_zone_device *pos = NULL;
> - int ret;
> + int id, ret;
>
> if (!ops || !ops->get_max_state || !ops->get_cur_state ||
> !ops->set_cur_state)
> @@ -901,7 +901,7 @@ __thermal_cooling_device_register(struct device_node *np,
> ret = ida_simple_get(&thermal_cdev_ida, 0, 0, GFP_KERNEL);
> if (ret < 0)
> goto out_kfree_cdev;
> - cdev->id = ret;
> + cdev->id = id = ret;

I'd prefer this to be two statements, but I can fix it up.

Daniel, would there be any issues if I applied it?

>
> cdev->type = kstrdup(type ? type : "", GFP_KERNEL);
> if (!cdev->type) {
> @@ -942,8 +942,9 @@ __thermal_cooling_device_register(struct device_node *np,
> out_kfree_type:
> kfree(cdev->type);
> put_device(&cdev->device);
> + cdev = NULL;
> out_ida_remove:
> - ida_simple_remove(&thermal_cdev_ida, cdev->id);
> + ida_simple_remove(&thermal_cdev_ida, id);
> out_kfree_cdev:
> kfree(cdev);
> return ERR_PTR(ret);
> --
> 2.25.1
>