Messages in this thread | | | Date | Mon, 12 Jun 2023 15:21:58 +0200 | Subject | Re: [PATCH] accel/qaic: Fix dereferencing freed memory | From | Christian König <> |
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Am 12.06.23 um 15:03 schrieb Pranjal Ramajor Asha Kanojiya: > > > 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.
Then why don't you use drm_prime_gem_destroy() which is the cleanup helper for imports created by ->gem_prime_import() ?
That looks pretty much identical to what you do here manually.
Regards, Christian.
> >> >>> } else { >>> /* Private buffer allocation path */ >>> qaic_free_sgt(bo->sgt); >>
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