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A self-targeted, disabled event with exclude_kernel=1 can therefore reach the filter compiler even at perf_event_paranoid=2. The .function suffix accepts any field of sizeof(long) and resolves its operand through kallsyms_lookup_name() and kallsyms_lookup_size_offset(). The success or failure of a numeric filter discloses whether an address belongs to a known kernel symbol range. On x86-64 this can be used to recover the randomized kernel image base. A named filter also exposes the resolved symbol range through the counter when the tracepoint field is controlled by the caller, as with a syscall argument. Pass the filter's perf origin to the predicate parser and require perf_allow_tracepoint() before resolving a .function operand. This uses the same sysctl, initial-namespace capability and LSM policy as raw tracepoint access, and closes both the numeric and named-symbol oracles. Do not change ordinary perf counting filters or filters created through the separately controlled tracefs interfaces. Fixes: e6745a4da964 ("tracing: Add a way to filter function addresses to function names") Cc: stable@vger.kernel.org Assisted-by: Codex:gpt-6-astra Signed-off-by: Kyle Zeng --- kernel/trace/trace_events_filter.c | 39 ++++++++++++++++++++++-------- 1 file changed, 29 insertions(+), 10 deletions(-) diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c index 2b46ca536045..0f8c2054f4a7 100644 --- a/kernel/trace/trace_events_filter.c +++ b/kernel/trace/trace_events_filter.c @@ -1625,12 +1625,18 @@ static int filter_pred_fn_call(struct filter_pred *pred, void *event) } } +struct filter_parse_data { + struct trace_event_call *call; + bool is_perf; +}; + /* Called when a predicate is encountered by predicate_parse() */ static int parse_pred(const char *str, void *data, int pos, struct filter_parse_error *pe, struct filter_pred **pred_ptr) { - struct trace_event_call *call = data; + struct filter_parse_data *pdata = data; + struct trace_event_call *call = pdata->call; struct ftrace_event_field *field; struct filter_pred *pred = NULL; unsigned long offset; @@ -1683,6 +1689,14 @@ static int parse_pred(const char *str, void *data, /* See if the field is a kernel function name */ if ((len = str_has_prefix(str + i, ".function"))) { + /* Even counting filters can disclose kernel addresses. */ + if (pdata->is_perf) { + ret = perf_allow_tracepoint(); + if (ret) { + parse_error(pe, ret, pos + i); + return ret; + } + } function = true; i += len; } @@ -2205,8 +2219,12 @@ static int calc_stack(const char *str, int *parens, int *preds, int *err) static int process_preds(struct trace_event_call *call, const char *filter_string, struct event_filter *filter, - struct filter_parse_error *pe) + struct filter_parse_error *pe, bool is_perf) { + struct filter_parse_data data = { + .call = call, + .is_perf = is_perf, + }; struct prog_entry *prog; int nr_parens; int nr_preds; @@ -2232,7 +2250,7 @@ static int process_preds(struct trace_event_call *call, return -EINVAL; prog = predicate_parse(filter_string, nr_parens, nr_preds, - parse_pred, call, pe); + parse_pred, &data, pe); if (IS_ERR(prog)) return PTR_ERR(prog); @@ -2281,7 +2299,7 @@ static int process_system_preds(struct trace_subsystem_dir *dir, if (!filter->filter_string) goto fail_mem; - err = process_preds(file->event_call, filter_string, filter, pe); + err = process_preds(file->event_call, filter_string, filter, pe, false); if (err) { filter_disable(file); parse_error(pe, FILT_ERR_BAD_SUBSYS_FILTER, 0); @@ -2377,6 +2395,7 @@ static void create_filter_finish(struct filter_parse_error *pe) * @call: trace_event_call to create a filter for * @filter_string: filter string * @set_str: remember @filter_str and enable detailed error in filter + * @is_perf: filter is being created for a perf event * @filterp: out param for created filter (always updated on return) * Must be a pointer that references a NULL pointer. * @@ -2391,7 +2410,7 @@ static void create_filter_finish(struct filter_parse_error *pe) */ static int create_filter(struct trace_array *tr, struct trace_event_call *call, - char *filter_string, bool set_str, + char *filter_string, bool set_str, bool is_perf, struct event_filter **filterp) { struct filter_parse_error *pe = NULL; @@ -2405,7 +2424,7 @@ static int create_filter(struct trace_array *tr, if (err) return err; - err = process_preds(call, filter_string, *filterp, pe); + err = process_preds(call, filter_string, *filterp, pe, is_perf); if (err && set_str) append_filter_err(tr, pe, *filterp); create_filter_finish(pe); @@ -2418,7 +2437,7 @@ int create_event_filter(struct trace_array *tr, char *filter_str, bool set_str, struct event_filter **filterp) { - return create_filter(tr, call, filter_str, set_str, filterp); + return create_filter(tr, call, filter_str, set_str, false, filterp); } /** @@ -2476,7 +2495,7 @@ int apply_event_filter(struct trace_event_file *file, char *filter_string) return 0; } - err = create_filter(file->tr, call, filter_string, true, &filter); + err = create_filter(file->tr, call, filter_string, true, false, &filter); /* * Always swap the call filter with the new filter @@ -2721,7 +2740,7 @@ int ftrace_profile_set_filter(struct perf_event *event, int event_id, if (event->filter) return -EEXIST; - err = create_filter(NULL, call, filter_str, false, &filter); + err = create_filter(NULL, call, filter_str, false, true, &filter); if (err) goto free_filter; @@ -2868,7 +2887,7 @@ static __init int ftrace_test_event_filter(void) int err; err = create_filter(NULL, &event_ftrace_test_filter, - d->filter, false, &filter); + d->filter, false, false, &filter); if (err) { printk(KERN_INFO "Failed to get filter for '%s', err %d\n", base-commit: fd179f8a05be3ccae366b9b96e176b51fbe54aab