Den 31.12.2017 16.41, skrev Chris Wilson:
Quoting Noralf Trønnes (2017-12-31 13:58:40)
Clear the pointer so the buffer can be re-exported. Otherwise use after free happens in the next call to drm_gem_prime_handle_to_fd().
Signed-off-by: Noralf Trønnes noralf@tronnes.org
drivers/gpu/drm/drm_prime.c | 1 + 1 file changed, 1 insertion(+)
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c index 9a17725b0f7a..3214c0eb7466 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -343,6 +343,7 @@ void drm_gem_dmabuf_release(struct dma_buf *dma_buf)
/* drop the reference on the export fd holds */ drm_gem_object_put_unlocked(obj);
obj->dma_buf = NULL;obj->dma_buf holds a reference to the dma_buf, so to get to the dma_buf release we must have already called dma_buf_put(obj->dma_buf). See drm_gem_object_exported_dma_buf_free(). (Note you would do the obj->dma_buf = NULL before dropping the potentially last ref to obj.) A BUG_ON(obj->dma_buf) may help clarify the cache was already released.
Hmm, okay it was a shot in the dark. Maybe I can defer dumb_buffer and drm_framebuffer creation until fb_open and then free it all in fb_close. That would align fbdev emulation more with how DRM userspace operates. Let's see what assumptions the code has about drm_fb_helper->fb being set on probe...
Noralf.