[for-next,05/11] tracing/user_events: Ensure write index cannot be negative
Commit Message
From: Beau Belgrave <beaub@linux.microsoft.com>
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: 7f5a08c79df3 ("user_events: Add minimal support for trace_event into ftrace")
Reported-by: Doug Cook <dcook@linux.microsoft.com>
Signed-off-by: Beau Belgrave <beaub@linux.microsoft.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
kernel/trace/trace_events_user.c | 3 +++
tools/testing/selftests/user_events/ftrace_test.c | 5 +++++
2 files changed, 8 insertions(+)
@@ -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);
@@ -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) {