Messages in this thread | | | Date | Mon, 9 Jan 2023 01:30:29 +0200 | Subject | Re: [PATCH v2 4/8] drm/msm/dpu: Disallow unallocated resources to be returned | From | Dmitry Baryshkov <> |
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On 09/01/2023 01:28, Dmitry Baryshkov wrote: > On 22/12/2022 01:19, Marijn Suijten wrote: >> In the event that the topology requests resources that have not been >> created by the system (because they are typically not represented in >> dpu_mdss_cfg ^1), the resource(s) in global_state (in this case DSC >> blocks) remain NULL but will still be returned out of >> dpu_rm_get_assigned_resources, where the caller expects to get an array >> containing num_blks valid pointers (but instead gets these NULLs). >> >> To prevent this from happening, where null-pointer dereferences >> typically result in a hard-to-debug platform lockup, num_blks shouldn't >> increase past NULL blocks and will print an error and break instead. >> After all, max_blks represents the static size of the maximum number of >> blocks whereas the actual amount varies per platform. >> >> ^1: which can happen after a git rebase ended up moving additions to >> _dpu_cfg to a different struct which has the same patch context. >> >> Fixes: bb00a452d6f7 ("drm/msm/dpu: Refactor resource manager") >> Signed-off-by: Marijn Suijten <marijn.suijten@somainline.org> >> --- >> drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 5 +++++ >> 1 file changed, 5 insertions(+) > > I think the patch is not fully correct. Please check resource > availability during allocation. I wouldn't expect an error from > get_assigned_resources because of resource exhaustion. >
Another option, since allocation functions (except DSC) already have these safety checks: check error message to mention internal inconstency: allocated resource doesn't exist.
-- With best wishes Dmitry
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