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Pavel Skripkin authored
My local syzbot instance hit GPF in ttm_bo_release(). Unfortunately, syzbot didn't produce a reproducer for this, but I found out possible scenario: drm_gem_vram_create() <-- drm_gem_vram_object kzalloced (bo embedded in this object) ttm_bo_init() ttm_bo_init_reserved() ttm_resource_alloc() man->func->alloc() <-- allocation failure ttm_bo_put() ttm_bo_release() ttm_mem_io_free() <-- bo->resource == NULL passed as second argument *GPF* Added NULL check inside ttm_mem_io_free() to prevent reported GPF and make this function NULL save in future. Same problem was in ttm_bo_move_to_lru_tail() as Christian reported. ttm_bo_move_to_lru_tail() is called in ttm_bo_release() and mem pointer can be NULL as well as in ttm_mem_io_free(). Fail log: KASAN: null-ptr-deref in range [0x0000000000000020-0x0000000000000027] ... RIP: 0010:ttm_mem_io_free+0x28/0x170 drivers/gpu/drm/ttm/ttm_bo_util.c:66 .. Call Trace: ttm_bo_release+0xd94/0x10a0 drivers/gpu/drm/ttm/ttm_bo.c:422 kref_put include/linux/kref.h:65 [inline] ttm_bo_put drivers/gpu/drm/ttm/ttm_bo.c:470 [inline] ttm_bo_init_reserved+0x7cb/0x960 drivers/gpu/drm/ttm/ttm_bo.c:1050 ttm_bo_init+0x105/0x270 drivers/gpu/drm/ttm/ttm_bo.c:1074 drm_gem_vram_create+0x332/0x4c0 drivers/gpu/drm/drm_gem_vram_helper.c:228 Fixes: d3116756 ("drm/ttm: rename bo->mem and make it a pointer") Signed-off-by: Pavel Skripkin <paskripkin@gmail.com> Reviewed-by: Christian König <christian.koenig@amd.com> Signed-off-by: Christian König <christian.koenig@amd.com> Link: https://patchwork.freedesktop.org/patch/msgid/20210708112518.17271-1-paskripkin@gmail.com
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