From: Rijo Thomas Rijo-john.Thomas@amd.com

stable inclusion from stable-v5.10.199 commit da7ce52a2f6c468946195b116615297d3d113a27 category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I9AWJ5

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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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 Signed-off-by: sanglipeng sanglipeng1@jd.com --- drivers/tee/amdtee/core.c | 10 ++++++---- 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/tee/amdtee/core.c b/drivers/tee/amdtee/core.c index 297dc62bca29..a890eeabe065 100644 --- a/drivers/tee/amdtee/core.c +++ b/drivers/tee/amdtee/core.c @@ -217,12 +217,12 @@ static int copy_ta_binary(struct tee_context *ctx, void *ptr, void **ta, 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); @@ -277,7 +277,8 @@ int amdtee_open_session(struct tee_context *ctx, if (i >= TEE_NUM_SESSIONS) { pr_err("reached maximum session count %d\n", TEE_NUM_SESSIONS); 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; } @@ -290,7 +291,8 @@ int amdtee_open_session(struct tee_context *ctx, clear_bit(i, sess->sess_mask); spin_unlock(&sess->lock); handle_unload_ta(ta_handle); - kref_put(&sess->refcount, destroy_session); + kref_put_mutex(&sess->refcount, destroy_session, + &session_list_mutex); goto out; }

@@ -332,7 +334,7 @@ int amdtee_close_session(struct tee_context *ctx, u32 session) 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; }