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SubjectRe: [PATCH] drm/i915/gvt: don't dereference 'workload' before null checking it
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On Wed, 2018-03-21 at 19:06 +0000, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
>
> The pointer workload is dereferenced before it is null checked, hence
> there is a potential for a null pointer dereference on workload. Fix
> this by only dereferencing workload after it is null checked.
>
> Detected by CoverityScan, CID#1466017 ("Dereference before null check")

Maybe true, but is it possible for workload to be null?
Maybe the null test should be removed instead.

> Fixes: fa3dd623e559 ("drm/i915/gvt: keep oa config in shadow ctx")
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
> drivers/gpu/drm/i915/gvt/scheduler.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gvt/scheduler.c b/drivers/gpu/drm/i915/gvt/scheduler.c
> index 068126404151..f3010e365a48 100644
> --- a/drivers/gpu/drm/i915/gvt/scheduler.c
> +++ b/drivers/gpu/drm/i915/gvt/scheduler.c
> @@ -60,9 +60,9 @@ static void set_context_pdp_root_pointer(
> static void sr_oa_regs(struct intel_vgpu_workload *workload,
> u32 *reg_state, bool save)
> {
> - struct drm_i915_private *dev_priv = workload->vgpu->gvt->dev_priv;
> - u32 ctx_oactxctrl = dev_priv->perf.oa.ctx_oactxctrl_offset;
> - u32 ctx_flexeu0 = dev_priv->perf.oa.ctx_flexeu0_offset;
> + struct drm_i915_private *dev_priv;
> + u32 ctx_oactxctrl;
> + u32 ctx_flexeu0;
> int i = 0;
> u32 flex_mmio[] = {
> i915_mmio_reg_offset(EU_PERF_CNTL0),
> @@ -77,6 +77,10 @@ static void sr_oa_regs(struct intel_vgpu_workload *workload,
> if (!workload || !reg_state || workload->ring_id != RCS)
> return;
>
> + dev_priv = workload->vgpu->gvt->dev_priv;
> + ctx_oactxctrl = dev_priv->perf.oa.ctx_oactxctrl_offset;
> + ctx_flexeu0 = dev_priv->perf.oa.ctx_flexeu0_offset;
> +
> if (save) {
> workload->oactxctrl = reg_state[ctx_oactxctrl + 1];
>

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