CVE-2022-50553 — tracing/hist: Fix out-of-bound write on 'action_data.var_ref_idx'

Affected: Linux

In the Linux kernel, the following vulnerability has been resolved:

tracing/hist: Fix out-of-bound write on 'action_data.var_ref_idx'

When generate a synthetic event with many params and then create a trace action for it [1], kernel panic happened [2].

It is because that in trace_action_create() 'data->n_params' is up to SYNTH_FIELDS_MAX (current value is 64), and array 'data->var_ref_idx' keeps indices into array 'hist_data->var_refs' for each synthetic event param, but the length of 'data->var_ref_idx' is TRACING_MAP_VARS_MAX (current value is 16), so out-of-bound write happened when 'data->n_params' more than 16. In this case, 'data->match_data.event' is overwritten and eventually cause the panic.

To solve the issue, adjust the length of 'data->var_ref_idx' to be SYNTH_FIELDS_MAX and add sanity checks to avoid out-of-bound write.

[1] # cd /sys/kernel/tracing/ # echo "my_synth_event int v1; int v2; int v3; int v4; int v5; int v6;\ int v7; int v8; int v9; int v10; int v11; int v12; int v13; int v14;\ int v15; int v16; int v17; int v18; int v19; int v20; int v21; int v22;\ int v23; int v24; int v25; int v26; int v27; int v28; int v29; int v30;\ int v31; int v32; int v33; int v34; int v35; int v36; int v37; int v38;\ int v39; int v40; int v41; int v42; int v43; int v44; int v45; int v46;\ int v47; int v48; int v49; int v50; int v51; int v52; int v53; int v54;\ int v55; int v56; int v57; int v58; int v59; int v60; int v61; int v62;\ int v63" >> synthetic_events # echo…

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CVE-2022-50553 — tracing/hist: Fix out-of-bound write on 'action_data.var_ref_idx'