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

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Message-ID: <20200623135007.3105d067@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Tue, 23 Jun 2020 13:50:07 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Kaige Li <likaige@...ngson.cn>
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 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.