6.1-stable review patch. If anyone has any objections, please let me know.
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From: Rijo Thomas Rijo-john.Thomas@amd.com
commit f4384b3e54ea813868bb81a861bf5b2406e15d8f upstream.
There is a potential race condition in amdtee_close_session that may cause use-after-free in amdtee_open_session. For instance, if a session has refcount == 1, and one thread tries to free this session via:
kref_put(&sess->refcount, destroy_session);
the reference count will get decremented, and the next step would be to call destroy_session(). However, if in another thread, amdtee_open_session() is called before destroy_session() has completed execution, alloc_session() may return 'sess' that will be freed up later in destroy_session() leading to use-after-free in amdtee_open_session.
To fix this issue, treat decrement of sess->refcount and removal of 'sess' from session list in destroy_session() as a critical section, so that it is executed atomically.
Fixes: 757cc3e9ff1d ("tee: add AMD-TEE driver") Cc: stable@vger.kernel.org Signed-off-by: Rijo Thomas Rijo-john.Thomas@amd.com Reviewed-by: Sumit Garg sumit.garg@linaro.org Signed-off-by: Jens Wiklander jens.wiklander@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/tee/amdtee/core.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)
--- a/drivers/tee/amdtee/core.c +++ b/drivers/tee/amdtee/core.c @@ -217,12 +217,12 @@ unlock: return rc; }
+/* mutex must be held by caller */ static void destroy_session(struct kref *ref) { struct amdtee_session *sess = container_of(ref, struct amdtee_session, refcount);
- mutex_lock(&session_list_mutex); list_del(&sess->list_node); mutex_unlock(&session_list_mutex); kfree(sess); @@ -272,7 +272,8 @@ int amdtee_open_session(struct tee_conte 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); + kref_put_mutex(&sess->refcount, destroy_session, + &session_list_mutex); goto out; }
@@ -290,7 +291,8 @@ int amdtee_open_session(struct tee_conte 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); + kref_put_mutex(&sess->refcount, destroy_session, + &session_list_mutex); rc = -ENOMEM; goto out; } @@ -331,7 +333,7 @@ int amdtee_close_session(struct tee_cont handle_close_session(ta_handle, session_info); handle_unload_ta(ta_handle);
- kref_put(&sess->refcount, destroy_session); + kref_put_mutex(&sess->refcount, destroy_session, &session_list_mutex);
return 0; }