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tracing/user_events: Ensure write index cannot be negative

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[ Upstream commit cd98c93286a30cc4588dfd02453bec63c2f4acf4 ]

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: 7f5a08c79d ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Beau Belgrave 2023-04-25 15:51:04 -07:00 committed by Greg Kroah-Hartman
parent 6472a6d0c7
commit 0489c2b2c3
2 changed files with 8 additions and 0 deletions
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3
kernel/trace/trace_events_user.c
View File

@ -1398,6 +1398,9 @@ 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);

5
tools/testing/selftests/user_events/ftrace_test.c
View File

@ -294,6 +294,11 @@ 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) {