Re: [PATCH] thermal/core: fix a UAF bug in __thermal_cooling_device_register()
From: "Rafael J. Wysocki" <rafael@kernel.org>
Date: 2021-10-14 11:08:39
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On Thu, Oct 14, 2021 at 10:47 AM Ziyang Xuan [off-list ref] wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- drivers/thermal/thermal_core.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)diff --git a/drivers/thermal/thermal_core.c b/drivers/thermal/thermal_core.c index 97ef9b040b84..ee7453944ccb 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)@@ -898,10 +898,10 @@ __thermal_cooling_device_register(struct device_node *np, if (!cdev) return ERR_PTR(-ENOMEM); - ret = ida_simple_get(&thermal_cdev_ida, 0, 0, GFP_KERNEL); - if (ret < 0) + id = ida_simple_get(&thermal_cdev_ida, 0, 0, GFP_KERNEL); + if (id < 0)
ret = id; is missing here.
goto out_kfree_cdev;
However, IMO it would be better to leave the code as is above and do id = ret; here.
quoted hunk ↗ jump to hunk
- cdev->id = ret; + cdev->id = id; 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); --