linux-kernel - Re: [PATCH] net: caif: Fix a sleep-in-atomic bug in cfpkt_create

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Message-Id: <20170610.182129.1342772715077530967.davem@davemloft.net>
Date:   Sat, 10 Jun 2017 18:21:29 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     baijiaju1990@....com
Cc:     dmitry.tarnyagin@...kless.no, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: caif: Fix a sleep-in-atomic bug in
 cfpkt_create_pfx

From: Jia-Ju Bai <baijiaju1990@....com>
Date: Sat, 10 Jun 2017 16:49:39 +0800

> The kernel may sleep under a rcu read lock in cfpkt_create_pfx, and the
> function call path is:
> cfcnfg_linkup_rsp (acquire the lock by rcu_read_lock)
>   cfctrl_linkdown_req
>     cfpkt_create
>       cfpkt_create_pfx
>         alloc_skb(GFP_KERNEL) --> may sleep
> cfserl_receive (acquire the lock by rcu_read_lock)
>   cfpkt_split
>     cfpkt_create_pfx
>       alloc_skb(GFP_KERNEL) --> may sleep
> 
> There is "in_interrupt" in cfpkt_create_pfx to decide use "GFP_KERNEL" or
> "GFP_ATOMIC". In this situation, "GFP_KERNEL" is used because the function 
> is called under a rcu read lock, instead in interrupt.
> 
> To fix it, only "GFP_ATOMIC" is used in cfpkt_create_pfx.
> 
> Signed-off-by: Jia-Ju Bai <baijiaju1990@....com>

Applied and queued up for -stable.