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tee: amdtee: fix use-after-free vulnerability in amdtee_close_session

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commit f4384b3e54 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: 757cc3e9ff ("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>
This commit is contained in:
Rijo Thomas 2023-09-29 12:30:24 +05:30 committed by Greg Kroah-Hartman
parent b8ec40a90a
commit 1680c82929
1 changed files with 6 additions and 4 deletions
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10
drivers/tee/amdtee/core.c
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@ -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_context *ctx,
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_context *ctx,
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_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;
}