linux-kernel - Re: [PATCH RESEND] net/cisco: Fix a sleep-in-atomic-context bug in enic_init_affinity

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Message-ID: <f12f40fe-7c9a-6ba8-f2ff-daf315030258@loongson.cn>
Date:   Wed, 24 Jun 2020 10:07:16 +0800
From:   Kaige Li <likaige@...ngson.cn>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Christian Benvenuti <benve@...co.com>,
        Govindarajulu Varadarajan <_govind@....com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Xuefeng Li <lixuefeng@...ngson.cn>,
        Tiezhu Yang <yangtiezhu@...ngson.cn>
Subject: Re: [PATCH RESEND] net/cisco: Fix a sleep-in-atomic-context bug in
 enic_init_affinity_hint()


On 06/24/2020 04:50 AM, Jakub Kicinski wrote:
> On Tue, 23 Jun 2020 16:13:09 +0800 Kaige Li wrote:
>> The kernel module may sleep with holding a spinlock.
>>
>> The function call paths (from bottom to top) are:
>>
>> [FUNC] zalloc_cpumask_var(GFP_KERNEL)
>> drivers/net/ethernet/cisco/enic/enic_main.c, 125: zalloc_cpumask_var in enic_init_affinity_hint
>> drivers/net/ethernet/cisco/enic/enic_main.c, 1918: enic_init_affinity_hint in enic_open
>> drivers/net/ethernet/cisco/enic/enic_main.c, 2348: enic_open in enic_reset
>> drivers/net/ethernet/cisco/enic/enic_main.c, 2341: spin_lock in enic_reset
>>
>> To fix this bug, GFP_KERNEL is replaced with GFP_ATOMIC.
>>
>> Signed-off-by: Kaige Li <likaige@...ngson.cn>
> I don't think this is sufficient. Calling open with a spin lock held
> seems like a very bad idea. At a quick look the driver also calls
> request_irq() from open - request_irq() can sleep.

You are right. Should I do spin_unlock before the enic_open, or remove
spin_lock in enic_reset?

Thank you.