Commit cd98c932 authored by Beau Belgrave's avatar Beau Belgrave Committed by Steven Rostedt (Google)
Browse files

tracing/user_events: Ensure write index cannot be negative 

The write index indicates which event the data is for and accesses a
per-file array. The index is passed by user processes during write()
calls as the first 4 bytes. Ensure that it cannot be negative by
returning -EINVAL to prevent out of bounds accesses.

Update ftrace self-test to ensure this occurs properly.

Link: https://lkml.kernel.org/r/20230425225107.8525-2-beaub@linux.microsoft.com



Fixes: 7f5a08c7 ("user_events: Add minimal support for trace_event into ftrace")
Reported-by: default avatarDoug Cook <dcook@linux.microsoft.com>
Signed-off-by: default avatarBeau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent 96928d90

kernel/trace/trace_events_user.c

+3 −0
Original line number Diff line number Diff line
@@ -1824,6 +1824,9 @@ static ssize_t user_events_write_core(struct file *file, struct iov_iter *i) 
	if (unlikely(copy_from_iter(&idx, sizeof(idx), i) != sizeof(idx)))

		return -EFAULT;



	if (idx < 0)

		return -EINVAL;



	rcu_read_lock_sched();



	refs = rcu_dereference_sched(info->refs);

tools/testing/selftests/user_events/ftrace_test.c

+5 −0
Original line number Diff line number Diff line
@@ -296,6 +296,11 @@ TEST_F(user, write_events) { 
	ASSERT_NE(-1, writev(self->data_fd, (const struct iovec *)io, 3));

	after = trace_bytes();

	ASSERT_GT(after, before);



	/* Negative index should fail with EINVAL */

	reg.write_index = -1;

	ASSERT_EQ(-1, writev(self->data_fd, (const struct iovec *)io, 3));

	ASSERT_EQ(EINVAL, errno);

}



TEST_F(user, write_fault) {