Commit 3c25fc97 authored by Marco Elver's avatar Marco Elver Committed by Peter Zijlstra
Browse files

perf: Copy perf_event_attr::sig_data on modification 



The intent has always been that perf_event_attr::sig_data should also be
modifiable along with PERF_EVENT_IOC_MODIFY_ATTRIBUTES, because it is
observable by user space if SIGTRAP on events is requested.

Currently only PERF_TYPE_BREAKPOINT is modifiable, and explicitly copies
relevant breakpoint-related attributes in hw_breakpoint_copy_attr().
This misses copying perf_event_attr::sig_data.

Since sig_data is not specific to PERF_TYPE_BREAKPOINT, introduce a
helper to copy generic event-type-independent attributes on
modification.

Fixes: 97ba62b2 ("perf: Add support for SIGTRAP on perf events")
Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Signed-off-by: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarDmitry Vyukov <dvyukov@google.com>
Link: https://lore.kernel.org/r/20220131103407.1971678-1-elver@google.com
parent a01994f5

kernel/events/core.c

+16 −0
Original line number Diff line number Diff line
@@ -3238,6 +3238,15 @@ static int perf_event_modify_breakpoint(struct perf_event *bp, 
	return err;

}



/*

 * Copy event-type-independent attributes that may be modified.

 */

static void perf_event_modify_copy_attr(struct perf_event_attr *to,

					const struct perf_event_attr *from)

{

	to->sig_data = from->sig_data;

}



static int perf_event_modify_attr(struct perf_event *event,

				  struct perf_event_attr *attr)

{
@@ -3260,10 +3269,17 @@ static int perf_event_modify_attr(struct perf_event *event, 
	WARN_ON_ONCE(event->ctx->parent_ctx);



	mutex_lock(&event->child_mutex);

	/*

	 * Event-type-independent attributes must be copied before event-type

	 * modification, which will validate that final attributes match the

	 * source attributes after all relevant attributes have been copied.

	 */

	perf_event_modify_copy_attr(&event->attr, attr);

	err = func(event, attr);

	if (err)

		goto out;

	list_for_each_entry(child, &event->child_list, child_list) {

		perf_event_modify_copy_attr(&child->attr, attr);

		err = func(child, attr);

		if (err)

			goto out;