| Message ID | 20230109231556.344977-1-marijn.suijten@somainline.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v3] drm/msm/dpu: Disallow unallocated resources to be returned | expand |
On 10/01/2023 01:15, 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, until their allocation/assignment is being sanity-checked in > "drm/msm/dpu: Reject topologies for which no DSC blocks are available") > 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> > --- > > Changes since v2: > - Dropped all 7 other patches that were queued for -next; > - Reworded error message to clarify that the requested resource should > have already been allocated, rather than sounding like > dpu_rm_get_assigned_resources is (re)allocating/(re)assigning > resources here; > - This patch is now (implicitly!) based after "drm/msm/dpu: Reject > topologies for which no DSC blocks are available", which should make > it impossible to reach this condition, making it more of a safeguard > in case of future code changes and/or hidden issues: and is more > clearly conveyed in the patch message as well. > > v2: https://lore.kernel.org/linux-arm-msm/20221221231943.1961117-5-marijn.suijten@somainline.org/ > > drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 5 +++++ > 1 file changed, 5 insertions(+) Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
On Tue, 10 Jan 2023 00:15:55 +0100, 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, until their allocation/assignment is being sanity-checked in > "drm/msm/dpu: Reject topologies for which no DSC blocks are available") > 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). > > [...] Applied, thanks! [1/1] drm/msm/dpu: Disallow unallocated resources to be returned https://gitlab.freedesktop.org/lumag/msm/-/commit/abc40122d9a6 Best regards,
diff --git a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c index 73b3442e7467..7ada957adbbb 100644 --- a/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c +++ b/drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c @@ -660,6 +660,11 @@ int dpu_rm_get_assigned_resources(struct dpu_rm *rm, blks_size, enc_id); break; } + if (!hw_blks[i]) { + DPU_ERROR("Allocated resource %d unavailable to assign to enc %d\n", + type, enc_id); + break; + } blks[num_blks++] = hw_blks[i]; }
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, until their allocation/assignment is being sanity-checked in "drm/msm/dpu: Reject topologies for which no DSC blocks are available") 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> --- Changes since v2: - Dropped all 7 other patches that were queued for -next; - Reworded error message to clarify that the requested resource should have already been allocated, rather than sounding like dpu_rm_get_assigned_resources is (re)allocating/(re)assigning resources here; - This patch is now (implicitly!) based after "drm/msm/dpu: Reject topologies for which no DSC blocks are available", which should make it impossible to reach this condition, making it more of a safeguard in case of future code changes and/or hidden issues: and is more clearly conveyed in the patch message as well. v2: https://lore.kernel.org/linux-arm-msm/20221221231943.1961117-5-marijn.suijten@somainline.org/ drivers/gpu/drm/msm/disp/dpu1/dpu_rm.c | 5 +++++ 1 file changed, 5 insertions(+)