linux-kernel - Re: [PATCH] opp: fix a missing check on list iterator

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Message-Id: <20220328091339.27021-1-xiam0nd.tong@gmail.com>
Date:   Mon, 28 Mar 2022 17:13:39 +0800
From:   Xiaomeng Tong <xiam0nd.tong@...il.com>
To:     viresh.kumar@...aro.org
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org, nm@...com,
        rafael.j.wysocki@...el.com, sboyd@...nel.org,
        stable@...r.kernel.org, vireshk@...nel.org, xiam0nd.tong@...il.com
Subject: Re: [PATCH] opp: fix a missing check on list iterator

On Mon, 28 Mar 2022 14:20:57 +0530, Viresh Kumar wrote:
> On 28-03-22, 15:43, Xiaomeng Tong wrote:
> > No. the conditon to call opp_migrate_dentry(opp_dev, opp_table); is:
> > if (!list_is_singular(&opp_table->dev_list)), 
> > 
> > while list_is_singlular is: !list_empty(head) && (head->next == head->prev);
> > 
> > so the condition is: list_empty(head) || (head->next != head->prev)
> > 
> > if the list is empty, the bug can be triggered.
> 
> List can't be empty here by design. It will be a huge bug in that
> case, which should lead to crash somewhere.
> 

There is anther condition to trigger this bug: the list is not empty and
no element found (if (iter != opp_dev)).

--
Xiaomeng Tong