Messages in this thread | | | Date | Mon, 12 Jun 2023 18:33:04 +0530 | Subject | Re: [PATCH] accel/qaic: Fix dereferencing freed memory | From | Pranjal Ramajor Asha Kanojiya <> |
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On 6/12/2023 4:52 PM, Christian König wrote: > > > Am 10.06.23 um 04:12 schrieb Sukrut Bellary: >> smatch warning: >> drivers/accel/qaic/qaic_data.c:620 qaic_free_object() error: >> dereferencing freed memory 'obj->import_attach' >> >> obj->import_attach is detached and freed using dma_buf_detach(). >> But used after free to decrease the dmabuf ref count using >> dma_buf_put(). >> >> Fixes: ff13be830333 ("accel/qaic: Add datapath") >> Signed-off-by: Sukrut Bellary <sukrut.bellary@linux.com> >> --- >> drivers/accel/qaic/qaic_data.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/accel/qaic/qaic_data.c >> b/drivers/accel/qaic/qaic_data.c >> index e42c1f9ffff8..7cba4d680ea8 100644 >> --- a/drivers/accel/qaic/qaic_data.c >> +++ b/drivers/accel/qaic/qaic_data.c >> @@ -613,11 +613,13 @@ static int qaic_gem_object_mmap(struct >> drm_gem_object *obj, struct vm_area_struc >> static void qaic_free_object(struct drm_gem_object *obj) >> { >> struct qaic_bo *bo = to_qaic_bo(obj); >> + struct dma_buf *dmabuf; > > Maybe move that variable into the if. > >> if (obj->import_attach) { >> /* DMABUF/PRIME Path */ >> + dmabuf = obj->import_attach->dmabuf; >> dma_buf_detach(obj->import_attach->dmabuf, obj->import_attach); >> - dma_buf_put(obj->import_attach->dmabuf); >> + dma_buf_put(dmabuf); > > I strongly assume you are not using the GEM prime helpers for this? > > Christian.
Driver uses drm_gem_prime_fd_to_handle() helper function but it also registers for ->gem_prime_import() which is internally called by drm_gem_prime_fd_to_handle(). All the operations done in gem_prime_import() are undone here.
> >> } else { >> /* Private buffer allocation path */ >> qaic_free_sgt(bo->sgt); >
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