Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider: - [High] tracing: check_synth_field regression for __bitmask and stacktraces - [High] tracing: arbitrary memory read via scalar to string synthetic field mapping --
commit 4813d717e995df13871068dd6fd996711ca8965d Author: Lee Jones <[email protected]> tracing/histograms: Reject non-stacktrace fields for synthetic stacktrace fields In check_synth_field(), when a synthetic event field is a stacktrace and the histogram field is not a "long[" stacktrace array, validation falls through to the generic size and signedness comparison. This allows any 8-byte signed scalar histogram field to pass the fallback check and be dereferenced as a kernel stacktrace pointer. This commit attempts to reject these mismatches by enforcing that field->is_stack matches the "long[" type. > diff --git a/kernel/trace/trace_events_hist.c > b/kernel/trace/trace_events_hist.c > index 8af97fd4ee2d5..b09f5043e1543 100644 > --- a/kernel/trace/trace_events_hist.c > +++ b/kernel/trace/trace_events_hist.c > @@ -3946,7 +3946,10 @@ static int check_synth_field(struct synth_event *event, > && field->is_dynamic) > return 0; > > - if (strstr(hist_field->type, "long[") && field->is_stack) > + if (!!strstr(hist_field->type, "long[") != field->is_stack) > + return -EINVAL; [Severity: High] Does this heuristic falsely match the long[ substring in __data_loc unsigned long[] from __bitmask and __cpumask fields? If is_stack == false, this logic seems to falsely reject valid mappings. If is_stack == true, this appears to bypass validation and allow a 32-bit __data_loc integer to be passed as the field value. Could this 32-bit integer then be cast to a pointer and dereferenced in trace_events_synth.c:get_field_size() and trace_stack(), potentially causing a kernel panic? > + > + if (field->is_stack) > return 0; > > if (strcmp(field->type, hist_field->type) != 0) { > if (field->size != hist_field->size || > (!field->is_string && field->is_signed != > hist_field->is_signed)) > return -EINVAL; > } [Severity: High] It looks like this fallback logic fails to reject a scalar-to-string mapping. When creating a dynamic string synthetic field, its size is set to sizeof(u64) and is_string is true. Because field->size equals hist_field->size (8 bytes) and !field->is_string short-circuits the type/signedness check, will an 8-byte scalar successfully map to a dynamic string? If an attacker-controlled scalar is passed, can it be cast to a kernel pointer in trace_events_synth.c:trace_string() and used with fetch_store_strlen() to arbitrarily read kernel memory? -- Sashiko AI review ยท https://sashiko.dev/#/patchset/[email protected]?part=1
