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SubjectRe: Oops (request_key_auth_describe) while running cve-2016-7042 from LTP
Date
Hillf Danton <hdanton@sina.com> wrote:

> - struct request_key_auth *rka = dereference_key_rcu(key);
> + struct request_key_auth *rka;
> +
> + rcu_read_lock();
> + rka = dereference_key_rcu(key);

This shouldn't help as the caller, proc_keys_show(), is holding the RCU read
lock across the call. The end of the function reads:

if (key->type->describe)
key->type->describe(key, m);
seq_putc(m, '\n');

rcu_read_unlock();
return 0;
}

and the documentation says "This method will be called with the RCU read lock
held".

I suspect the actual bugfix is this bit:

> + if (!rka)
> + goto out;

David

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