6.10-stable review patch. If anyone has any objections, please let me know.
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From: Tobias Jakobi tjakobi@math.uni-bielefeld.de
commit e835d5144f5ef78e4f8828c63e2f0d61144f283a upstream.
dc_state_destruct() nulls the resource context of the DC state. The pipe context passed to dcn35_set_drr() is a member of this resource context.
If dc_state_destruct() is called parallel to the IRQ processing (which calls dcn35_set_drr() at some point), we can end up using already nulled function callback fields of struct stream_resource.
The logic in dcn35_set_drr() already tries to avoid this, by checking tg against NULL. But if the nulling happens exactly after the NULL check and before the next access, then we get a race.
Avoid this by copying tg first to a local variable, and then use this variable for all the operations. This should work, as long as nobody frees the resource pool where the timing generators live.
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3142 Fixes: 06ad7e164256 ("drm/amd/display: Destroy DC context while keeping DML and DML2") Signed-off-by: Tobias Jakobi tjakobi@math.uni-bielefeld.de Reviewed-by: Harry Wentland harry.wentland@amd.com Signed-off-by: Mario Limonciello mario.limonciello@amd.com Signed-off-by: Alex Deucher alexander.deucher@amd.com (cherry picked from commit 0607a50c004798a96e62c089a4c34c220179dcb5) Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/amd/display/dc/hwss/dcn35/dcn35_hwseq.c | 20 +++++++++------- 1 file changed, 12 insertions(+), 8 deletions(-)
--- a/drivers/gpu/drm/amd/display/dc/hwss/dcn35/dcn35_hwseq.c +++ b/drivers/gpu/drm/amd/display/dc/hwss/dcn35/dcn35_hwseq.c @@ -1371,7 +1371,13 @@ void dcn35_set_drr(struct pipe_ctx **pip params.vertical_total_mid_frame_num = adjust.v_total_mid_frame_num;
for (i = 0; i < num_pipes; i++) { - if ((pipe_ctx[i]->stream_res.tg != NULL) && pipe_ctx[i]->stream_res.tg->funcs) { + /* dc_state_destruct() might null the stream resources, so fetch tg + * here first to avoid a race condition. The lifetime of the pointee + * itself (the timing_generator object) is not a problem here. + */ + struct timing_generator *tg = pipe_ctx[i]->stream_res.tg; + + if ((tg != NULL) && tg->funcs) { struct dc_crtc_timing *timing = &pipe_ctx[i]->stream->timing; struct dc *dc = pipe_ctx[i]->stream->ctx->dc;
@@ -1384,14 +1390,12 @@ void dcn35_set_drr(struct pipe_ctx **pip num_frames = 2 * (frame_rate % 60); } } - if (pipe_ctx[i]->stream_res.tg->funcs->set_drr) - pipe_ctx[i]->stream_res.tg->funcs->set_drr( - pipe_ctx[i]->stream_res.tg, ¶ms); + if (tg->funcs->set_drr) + tg->funcs->set_drr(tg, ¶ms); if (adjust.v_total_max != 0 && adjust.v_total_min != 0) - if (pipe_ctx[i]->stream_res.tg->funcs->set_static_screen_control) - pipe_ctx[i]->stream_res.tg->funcs->set_static_screen_control( - pipe_ctx[i]->stream_res.tg, - event_triggers, num_frames); + if (tg->funcs->set_static_screen_control) + tg->funcs->set_static_screen_control( + tg, event_triggers, num_frames); } } }