Re: [RFC PATCH] drm/sched: Fix a UAF on drm_sched_fence::sched

[kernel test robot <lkp@intel.com>]

Hi Boris,

[This is a private test report for your RFC patch.]
kernel test robot noticed the following build errors:

[auto build test ERROR on drm/drm-next]
[also build test ERROR on drm-misc/drm-misc-next linus/master v6.11-rc6 next-20240830]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Boris-Brezillon/drm-sched-Fix-a-UAF-on-drm_sched_fence-sched/20240830-012038
base:   git://anongit.freedesktop.org/drm/drm drm-next
patch link:    https://lore.kernel.org/r/20240829171238.609481-1-boris.brezillon%40collabora.com
patch subject: [RFC PATCH] drm/sched: Fix a UAF on drm_sched_fence::sched
config: i386-allmodconfig (https://download.01.org/0day-ci/archive/20240902/202409021023.EWUGtkoV-lkp@intel.com/config)
compiler: gcc-12 (Debian 12.2.0-14) 12.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240902/202409021023.EWUGtkoV-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202409021023.EWUGtkoV-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from drivers/gpu/drm/amd/amdgpu/amdgpu_ring.h:28,
                    from drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.h:29,
                    from drivers/gpu/drm/amd/amdgpu/amdgpu.h:43,
                    from drivers/gpu/drm/amd/amdgpu/amdgpu_doorbell_mgr.c:25:
   include/drm/gpu_scheduler.h: In function 'drm_sched_fence_timeline_release':
>> include/drm/gpu_scheduler.h:290:9: error: implicit declaration of function 'kfree' [-Werror=implicit-function-declaration]
     290 |         kfree(tl->name);
         |         ^~~~~
   In file included from include/linux/resource_ext.h:11,
                    from include/linux/pci.h:40,
                    from drivers/gpu/drm/amd/amdgpu/amdgpu.h:52:
   include/linux/slab.h: At top level:
   include/linux/slab.h:278:6: warning: conflicting types for 'kfree'; have 'void(const void *)'
     278 | void kfree(const void *objp);
         |      ^~~~~
   include/drm/gpu_scheduler.h:290:9: note: previous implicit declaration of 'kfree' with type 'void(const void *)'
     290 |         kfree(tl->name);
         |         ^~~~~
   cc1: some warnings being treated as errors


vim +/kfree +290 include/drm/gpu_scheduler.h

   283	
   284	static inline void
   285	drm_sched_fence_timeline_release(struct kref *kref)
   286	{
   287		struct drm_sched_fence_timeline *tl =
   288			container_of(kref, struct drm_sched_fence_timeline, kref);
   289	
 > 290		kfree(tl->name);
   291		kfree(tl);
   292	}
   293	

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