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Subject: Re: [BUG] net: xfrm: Two possible sleep-in-atomic-context bugs
To:     Steffen Klassert <steffen.klassert@secunet.com>
Cc:     herbert@gondor.apana.org.au, davem@davemloft.net,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
References: <b74ebf58-16c0-4a51-a004-7ce9e6abde7a@gmail.com>
 <20180810053604.uopy5ziikf736p5o@gauss3.secunet.de>
From:   Jia-Ju Bai <baijiaju1990@gmail.com>
Message-ID: <b996cef6-530d-635a-2e28-eabca3387e2f@gmail.com>
Date:   Fri, 10 Aug 2018 15:30:40 +0800
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Thanks for your reply :)


On 2018/8/10 13:36, Steffen Klassert wrote:
> On Fri, Aug 10, 2018 at 10:02:42AM +0800, bai wrote:
>> The code may sleep in interrupt handler.
>> xfrm_trans_reinject() is an interrupt handler set in tasklet_init().
>> The function call paths (from bottom to top) in Linux-4.16 are:
>>
>> [FUNC] schedule_timeout
>> net/core/sock.c, 2044: schedule_timeout in sock_wait_for_wmem
>> net/core/sock.c, 2083: sock_wait_for_wmem in sock_alloc_send_pskb
>> net/core/sock.c, 2102: sock_alloc_send_pskb in sock_alloc_send_skb
>> net/ipv6/mcast.c, 1989: sock_alloc_send_skb in igmp6_send
> igmp6_send calls sock_alloc_send_skb with 'noblock = 1',
> this means that sock_wait_for_wmem is not executed in
> sock_alloc_send_pskb.
>
>> net/ipv6/mcast.c, 2391: igmp6_send in igmp6_join_group
>> net/ipv6/mcast.c, 670: igmp6_join_group in igmp6_group_added
>> net/ipv6/mcast.c, 914: igmp6_group_added in ipv6_dev_mc_inc
>> net/ipv6/ndisc.c, 379: ipv6_dev_mc_inc in pndisc_constructor
>> net/core/neighbour.c, 640: [FUNC_PTR]pndisc_constructor in pneigh_lookup
>> net/ipv6/ip6_output.c, 483: pneigh_lookup in ip6_forward
>> ./include/net/dst.h, 449: [FUNC_PTR]ip6_forward in dst_input
>> net/ipv6/ip6_input.c, 71: dst_input in ip6_rcv_finish
>> net/xfrm/xfrm_input.c, 511: [FUNC_PTR]ip6_rcv_finish in xfrm_trans_reinject
>>
>> [FUNC] kmalloc(GFP_KERNEL)
>> net/core/neighbour.c, 630: kmalloc in pneigh_lookup
>> net/ipv6/ip6_output.c, 483: pneigh_lookup in ip6_forward
> ip6_forward calls pneigh_lookup with 'creat = 0',
> this means that pneigh_lookup does not do the kmalloc.
>
>> ./include/net/dst.h, 449: [FUNC_PTR]ip6_forward in dst_input
>> net/ipv6/ip6_input.c, 71: dst_input in ip6_rcv_finish
>> net/xfrm/xfrm_input.c, 511: [FUNC_PTR]ip6_rcv_finish in xfrm_trans_reinject
>>
>> Note that [FUNC_PTR] means a function pointer call is used.
>>
>> I do not find a good way to fix them, so I only report.
>> These possible bugs are found by my static analysis tool (DSAC) and checked
>> by my code review.
> Both codepaths are ok, maybe you should fix your tool ;-)

It seems that the path condition checking in my tool needs to be improved.
I will do it, thanks :)


Best wishes,
Jia-Ju Bai