Commit f8502fba authored by Rijo Thomas's avatar Rijo Thomas Committed by Jens Wiklander
Browse files

tee: amdtee: fix race condition in amdtee_open_session 



There is a potential race condition in amdtee_open_session that may
lead to use-after-free. For instance, in amdtee_open_session() after
sess->sess_mask is set, and before setting:

    sess->session_info[i] = session_info;

if amdtee_close_session() closes this same session, then 'sess' data
structure will be released, causing kernel panic when 'sess' is
accessed within amdtee_open_session().

The solution is to set the bit sess->sess_mask as the last step in
amdtee_open_session().

Fixes: 757cc3e9 ("tee: add AMD-TEE driver")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarRijo Thomas <Rijo-john.Thomas@amd.com>
Acked-by: default avatarSumit Garg <sumit.garg@linaro.org>
Signed-off-by: default avatarJens Wiklander <jens.wiklander@linaro.org>
parent c9c3395d

drivers/tee/amdtee/core.c

+14 −15
Original line number Diff line number Diff line
@@ -267,35 +267,34 @@ int amdtee_open_session(struct tee_context *ctx, 
		goto out;

	}



	/* Open session with loaded TA */

	handle_open_session(arg, &session_info, param);

	if (arg->ret != TEEC_SUCCESS) {

		pr_err("open_session failed %d\n", arg->ret);

		handle_unload_ta(ta_handle);

		kref_put(&sess->refcount, destroy_session);

		goto out;

	}



	/* Find an empty session index for the given TA */

	spin_lock(&sess->lock);

	i = find_first_zero_bit(sess->sess_mask, TEE_NUM_SESSIONS);

	if (i < TEE_NUM_SESSIONS)

	if (i < TEE_NUM_SESSIONS) {

		sess->session_info[i] = session_info;

		set_session_id(ta_handle, i, &arg->session);

		set_bit(i, sess->sess_mask);

	}

	spin_unlock(&sess->lock);



	if (i >= TEE_NUM_SESSIONS) {

		pr_err("reached maximum session count %d\n", TEE_NUM_SESSIONS);

		handle_close_session(ta_handle, session_info);

		handle_unload_ta(ta_handle);

		kref_put(&sess->refcount, destroy_session);

		rc = -ENOMEM;

		goto out;

	}



	/* Open session with loaded TA */

	handle_open_session(arg, &session_info, param);

	if (arg->ret != TEEC_SUCCESS) {

		pr_err("open_session failed %d\n", arg->ret);

		spin_lock(&sess->lock);

		clear_bit(i, sess->sess_mask);

		spin_unlock(&sess->lock);

		handle_unload_ta(ta_handle);

		kref_put(&sess->refcount, destroy_session);

		goto out;

	}



	sess->session_info[i] = session_info;

	set_session_id(ta_handle, i, &arg->session);

out:

	free_pages((u64)ta, get_order(ta_size));

	return rc;