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perf inject: Fix itrace branch stack synthesis

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When using "perf inject --itrace=L" to synthesize branch stacks from
AUX data, several issues caused failures with the generated file:

1. The synthesized samples were delivered without the
   PERF_SAMPLE_BRANCH_STACK flag if it was not in the original event's
   sample_type. Fixed by using sample_type | evsel->synth_sample_type
   in intel_pt_do_synth_pebs_sample.

2. Modifying evsel->core.attr.sample_type early in __cmd_inject caused
   parse failures for subsequent records in the input file. Fixed by
   moving this modification to just before writing the header.

3. perf_event__repipe_sample was narrowed to only synthesize samples
   when branch stack injection was requested, and restored the use of
   perf_inject__cut_auxtrace_sample as a fallback to preserve
   functionality.

4. Potential Heap Overflow in perf_event__repipe_sample: Addressed by
   adding a check that prints an error and returns -EFAULT if the
   calculated event size exceeds PERF_SAMPLE_MAX_SIZE.

5. Header vs Payload Mismatch in __cmd_inject: Addressed by narrowing
   the condition so that HEADER_BRANCH_STACK is only set in the file
   header if add_last_branch was true.

6. NULL Pointer Dereference in intel-pt.c: When branch stack injection
   is requested (add_last_branch is true) but last_branch is false
   (e.g., perf inject --itrace=L), ptq->last_branch was not allocated.
   However, PEBS branch stack synthesis (via synth_sample_type) still
   forced LBR handling in do_synth_pebs_sample(), dereferencing the
   NULL ptq->last_branch pointer. Guarding the dereference is not
   sufficient because downstream sample size calculation and synthesis
   strictly require a non-NULL branch_stack when the bit is set.
   Fixed by ensuring ptq->last_branch is allocated in
   intel_pt_alloc_queue() when add_last_branch is requested.

7. Modifying event attributes in perf_event__repipe_attr in-place caused
   SIGSEGV on read-only mmap buffers in file mode and downstream parser
   breakage in pipe mode. Fixed by processing the unmodified attribute
   first, returning immediately in non-pipe mode, and correctly
   synthesizing a new attribute event for pipe output using
   perf_event__synthesize_attr. Also:
   - Added a size validation check and integer underflow protection when
     parsing n_ids.
   - Prevented Trailing ID memory corruption by zero-initializing the
     local attr copy and safely copying using min_t(size_t, sizeof(attr),
     event->attr.attr.size).
   - Resolved ID array parsing mismatch downstream by expanding attr.size
     to sizeof(struct perf_event_attr) before synthesis to guarantee
     perfect header/attribute size alignment.

8. Potential dangling pointer vulnerability in perf_event__repipe_sample:
   Addressed by restoring the original sample->branch_stack pointer
   before returning, including on early error return paths.

9. Off-by-one error in sample size check in perf_event__repipe_sample:
   Fixed by checking if sz >= PERF_SAMPLE_MAX_SIZE instead of >.

10. Unadvertised size field left in payload by cut_auxtrace_sample:
    Addressed by excluding the 8-byte size field from the copied
    payload to correctly match the cleared PERF_SAMPLE_AUX bit. Cut
    the AUX sample payload even if size is 0.

11. Inaccurate sample size calculation and uninitialized memory leaks in
    convert_sample_callchain: Fixed by replacing manual arithmetic with
    perf_event__sample_event_size and adding a bounds check against
    PERF_SAMPLE_MAX_SIZE.

12. Omission of branch_sample_type in file headers: Addressed by
    expanding older, smaller attributes to PERF_ATTR_SIZE_VER2 in
    __cmd_inject to ensure branch_sample_type is not silently omitted.

Fixes: 0f0aa5e069 ("perf inject: Add Instruction Tracing support")
Assisted-by: Gemini:gemini-3.1-pro-preview
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Dapeng Mi <dapeng1.mi@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Leo Yan <leo.yan@linux.dev>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Thomas Falcon <thomas.falcon@intel.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Ian Rogers 2026-05-18 15:43:25 -07:00 committed by Arnaldo Carvalho de Melo
parent 059e9100d8
commit daac18e7c4
2 changed files with 142 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

153
tools/perf/builtin-inject.c
View File

@ -216,12 +216,23 @@ static int perf_event__repipe_op4_synth(const struct perf_tool *tool,
return perf_event__repipe_synth(tool, event);
}
static int perf_event__repipe_synth_cb(const struct perf_tool *tool,
union perf_event *event,
struct perf_sample *sample __maybe_unused,
struct machine *machine __maybe_unused)
{
return perf_event__repipe_synth(tool, event);
}
static int perf_event__repipe_attr(const struct perf_tool *tool,
union perf_event *event,
struct evlist **pevlist)
{
struct perf_inject *inject = container_of(tool, struct perf_inject,
tool);
struct perf_event_attr attr;
size_t n_ids;
u64 *ids;
int ret;
ret = perf_event__process_attr(tool, event, pevlist);
@ -232,7 +243,37 @@ static int perf_event__repipe_attr(const struct perf_tool *tool,
if (!inject->output.is_pipe)
return 0;
return perf_event__repipe_synth(tool, event);
if (!inject->itrace_synth_opts.set)
return perf_event__repipe_synth(tool, event);
if (event->header.size < sizeof(struct perf_event_header) + sizeof(u64)) {
pr_err("Attribute event size %u is too small\n", event->header.size);
return -EINVAL;
}
if (event->header.size - sizeof(event->header) < event->attr.attr.size) {
pr_err("Attribute event size %u is too small for attr.size %u\n",
event->header.size, event->attr.attr.size);
return -EINVAL;
}
memset(&attr, 0, sizeof(attr));
memcpy(&attr, &event->attr.attr,
min_t(size_t, sizeof(attr), (size_t)event->attr.attr.size));
n_ids = event->header.size - sizeof(event->header) - event->attr.attr.size;
n_ids /= sizeof(u64);
ids = perf_record_header_attr_id(event);
attr.size = sizeof(struct perf_event_attr);
attr.sample_type &= ~PERF_SAMPLE_AUX;
if (inject->itrace_synth_opts.add_last_branch) {
attr.sample_type |= PERF_SAMPLE_BRANCH_STACK;
attr.branch_sample_type |= PERF_SAMPLE_BRANCH_HW_INDEX;
}
return perf_event__synthesize_attr(tool, &attr, (u32)n_ids, ids,
perf_event__repipe_synth_cb);
}
static int perf_event__repipe_event_update(const struct perf_tool *tool,
@ -331,8 +372,8 @@ perf_inject__cut_auxtrace_sample(struct perf_inject *inject,
union perf_event *event,
struct perf_sample *sample)
{
size_t sz1 = sample->aux_sample.data - (void *)event;
size_t sz2 = event->header.size - sample->aux_sample.size - sz1;
size_t sz1 = sample->aux_sample.data - (void *)event - sizeof(u64);
size_t sz2 = event->header.size - sample->aux_sample.size - (sz1 + sizeof(u64));
union perf_event *ev;
if (inject->event_copy == NULL) {
@ -343,13 +384,12 @@ perf_inject__cut_auxtrace_sample(struct perf_inject *inject,
ev = (union perf_event *)inject->event_copy;
if (sz1 > event->header.size || sz2 > event->header.size ||
sz1 + sz2 > event->header.size ||
sz1 < sizeof(struct perf_event_header) + sizeof(u64))
sz1 < sizeof(struct perf_event_header))
return event;
memcpy(ev, event, sz1);
memcpy((void *)ev + sz1, (void *)event + event->header.size - sz2, sz2);
ev->header.size = sz1 + sz2;
((u64 *)((void *)ev + sz1))[-1] = 0;
return ev;
}
@ -369,14 +409,77 @@ static int perf_event__repipe_sample(const struct perf_tool *tool,
struct perf_inject *inject = container_of(tool, struct perf_inject,
tool);
if (evsel && evsel->handler) {
if (evsel == NULL)
return perf_event__repipe_synth(tool, event);
if (evsel->handler) {
inject_handler f = evsel->handler;
return f(tool, event, sample, evsel, machine);
}
build_id__mark_dso_hit(tool, event, sample, evsel, machine);
if (inject->itrace_synth_opts.set && sample->aux_sample.size) {
if (inject->itrace_synth_opts.set &&
(inject->itrace_synth_opts.last_branch ||
inject->itrace_synth_opts.add_last_branch)) {
union perf_event *event_copy = (void *)inject->event_copy;
struct branch_stack dummy_bs = { .nr = 0, .hw_idx = 0 };
int err;
size_t sz;
u64 orig_type = evsel->core.attr.sample_type;
u64 orig_branch_type = evsel->core.attr.branch_sample_type;
struct branch_stack *orig_bs = sample->branch_stack;
if (event_copy == NULL) {
inject->event_copy = malloc(PERF_SAMPLE_MAX_SIZE);
if (!inject->event_copy)
return -ENOMEM;
event_copy = (void *)inject->event_copy;
}
if (!sample->branch_stack)
sample->branch_stack = &dummy_bs;
if (inject->itrace_synth_opts.add_last_branch) {
/* Temporarily add in type bits for synthesis. */
evsel->core.attr.sample_type |= PERF_SAMPLE_BRANCH_STACK;
evsel->core.attr.branch_sample_type |= PERF_SAMPLE_BRANCH_HW_INDEX;
}
evsel->core.attr.sample_type &= ~PERF_SAMPLE_AUX;
sz = perf_event__sample_event_size(sample, evsel->core.attr.sample_type,
evsel->core.attr.read_format,
evsel->core.attr.branch_sample_type);
if (sz >= PERF_SAMPLE_MAX_SIZE) {
pr_err("Sample size %zu exceeds max size %d\n", sz, PERF_SAMPLE_MAX_SIZE);
evsel->core.attr.sample_type = orig_type;
evsel->core.attr.branch_sample_type = orig_branch_type;
sample->branch_stack = orig_bs;
return -EFAULT;
}
event_copy->header.type = PERF_RECORD_SAMPLE;
event_copy->header.misc = event->header.misc;
event_copy->header.size = sz;
err = perf_event__synthesize_sample(event_copy, evsel->core.attr.sample_type,
evsel->core.attr.read_format,
evsel->core.attr.branch_sample_type, sample);
evsel->core.attr.sample_type = orig_type;
evsel->core.attr.branch_sample_type = orig_branch_type;
sample->branch_stack = orig_bs;
if (err) {
pr_err("Failed to synthesize sample\n");
return err;
}
event = event_copy;
} else if (inject->itrace_synth_opts.set &&
(evsel->core.attr.sample_type & PERF_SAMPLE_AUX)) {
event = perf_inject__cut_auxtrace_sample(inject, event, sample);
if (IS_ERR(event))
return PTR_ERR(event);
@ -397,7 +500,7 @@ static int perf_event__convert_sample_callchain(const struct perf_tool *tool,
struct callchain_cursor_node *node;
struct thread *thread;
u64 sample_type = evsel->core.attr.sample_type;
u32 sample_size = event->header.size;
size_t sz;
u64 i, k;
int ret;
@ -456,15 +559,18 @@ static int perf_event__convert_sample_callchain(const struct perf_tool *tool,
out:
memcpy(event_copy, event, sizeof(event->header));
/* adjust sample size for stack and regs */
sample_size -= sample->user_stack.size;
sample_size -= (hweight64(evsel->core.attr.sample_regs_user) + 1) * sizeof(u64);
sample_size += (sample->callchain->nr + 1) * sizeof(u64);
event_copy->header.size = sample_size;
/* remove sample_type {STACK,REGS}_USER for synthesize */
sample_type &= ~(PERF_SAMPLE_STACK_USER | PERF_SAMPLE_REGS_USER);
sz = perf_event__sample_event_size(sample, sample_type,
evsel->core.attr.read_format,
evsel->core.attr.branch_sample_type);
if (sz >= PERF_SAMPLE_MAX_SIZE) {
pr_err("Sample size %zu exceeds max size %d\n", sz, PERF_SAMPLE_MAX_SIZE);
return -EFAULT;
}
event_copy->header.size = sz;
ret = perf_event__synthesize_sample(event_copy, sample_type,
evsel->core.attr.read_format,
evsel->core.attr.branch_sample_type, sample);
@ -2442,12 +2548,27 @@ static int __cmd_inject(struct perf_inject *inject)
* synthesized hardware events, so clear the feature flag.
*/
if (inject->itrace_synth_opts.set) {
struct evsel *evsel;
perf_header__clear_feat(&session->header,
HEADER_AUXTRACE);
if (inject->itrace_synth_opts.last_branch ||
inject->itrace_synth_opts.add_last_branch)
evlist__for_each_entry(session->evlist, evsel) {
evsel->core.attr.sample_type &= ~PERF_SAMPLE_AUX;
}
if (inject->itrace_synth_opts.add_last_branch) {
perf_header__set_feat(&session->header,
HEADER_BRANCH_STACK);
evlist__for_each_entry(session->evlist, evsel) {
evsel->core.attr.sample_type |= PERF_SAMPLE_BRANCH_STACK;
if (evsel->core.attr.size < PERF_ATTR_SIZE_VER2)
evsel->core.attr.size = PERF_ATTR_SIZE_VER2;
evsel->core.attr.branch_sample_type |=
PERF_SAMPLE_BRANCH_HW_INDEX;
}
}
}
/*

8
tools/perf/util/intel-pt.c
View File

@ -1307,7 +1307,8 @@ static struct intel_pt_queue *intel_pt_alloc_queue(struct intel_pt *pt,
goto out_free;
}
if (pt->synth_opts.last_branch || pt->synth_opts.other_events) {
if (pt->synth_opts.last_branch || pt->synth_opts.add_last_branch ||
pt->synth_opts.other_events) {
unsigned int entry_cnt = max(LBRS_MAX, pt->br_stack_sz);
ptq->last_branch = intel_pt_alloc_br_stack(entry_cnt);
@ -2505,7 +2506,7 @@ static int intel_pt_do_synth_pebs_sample(struct intel_pt_queue *ptq, struct evse
intel_pt_add_xmm(intr_regs, pos, items, regs_mask);
}
if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
if ((sample_type | evsel->synth_sample_type) & PERF_SAMPLE_BRANCH_STACK) {
if (items->mask[INTEL_PT_LBR_0_POS] ||
items->mask[INTEL_PT_LBR_1_POS] ||
items->mask[INTEL_PT_LBR_2_POS]) {
@ -2576,7 +2577,8 @@ static int intel_pt_do_synth_pebs_sample(struct intel_pt_queue *ptq, struct evse
sample.transaction = txn;
}
ret = intel_pt_deliver_synth_event(pt, event, &sample, sample_type);
ret = intel_pt_deliver_synth_event(pt, event, &sample,
sample_type | evsel->synth_sample_type);
perf_sample__exit(&sample);
return ret;
}