linux-kernel - Re: [PATCH v3] wifi: ath9k: fix printk specifier

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Date:   Wed, 19 Jul 2023 09:25:03 +0800
From:   Dongliang Mu <dzm91@...t.edu.cn>
To:     Toke Høiland-Jørgensen <toke@...e.dk>,
        Jonas Gorski <jonas.gorski@...il.com>
Cc:     Kalle Valo <kvalo@...nel.org>, linux-wireless@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] wifi: ath9k: fix printk specifier


On 2023/7/7 21:44, Toke Høiland-Jørgensen wrote:
> Jonas Gorski <jonas.gorski@...il.com> writes:
>
>> On Thu, 6 Jul 2023 at 13:39, Toke Høiland-Jørgensen <toke@...e.dk> wrote:
>>> Dongliang Mu <dzm91@...t.edu.cn> writes:
>>>
>>>> Smatch reports:
>>>>
>>>> ath_pci_probe() warn: argument 4 to %lx specifier is cast from pointer
>>>> ath_ahb_probe() warn: argument 4 to %lx specifier is cast from pointer
>>>>
>>>> Fix it by modifying %lx to %p in printk.
>>>>
>>>> Signed-off-by: Dongliang Mu <dzm91@...t.edu.cn>
>>> Third time is the charm! :)
>>>
>>> Acked-by: Toke Høiland-Jørgensen <toke@...e.dk>
>> But do we *want* to replace %lx with %p? Because this now causes a
>> change in behavior, as the kernel will omit the pointer's address,
>> while before it printed the actual memory address. Using %px would
>> have kept the original behavior.
> So this is basically an informational log message, which really
> shouldn't be leaking kernel pointer addresses. So I think %p is the
> right choice here, and if someone wants to see the real address for
> debugging they should be booting with no_hash_pointers.
>
>> So if the change is desired, it should be noted in the commit message.
> That is a fair point, documenting this in the commit message would be
> good...

Hi Toke,

What's the next? Patch v4 with a note at the end, like the following,

"Note that %p would by default print a hashed value without leaking the 
kernel pointer to user space."


> -Toke