linux-kernel - Re: net: sctp: possible dereference after freeing

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Date:	Sat, 19 Oct 2013 08:49:10 -0300
From:	Geyslan Gregório Bem <geyslan@...il.com>
To:	Vlad Yasevich <vyasevich@...il.com>
Cc:	Neil Horman <nhorman@...driver.com>,
	"David S. Miller" <davem@...emloft.net>,
	linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: net: sctp: possible dereference after freeing

2013/10/19 Geyslan Gregório Bem <geyslan@...il.com>:
> Hi maintainers,
>
> I would like to know if these are catches:
>
> /net/sctp/endpointola.c (281)
> static void sctp_endpoint_destroy(struct sctp_endpoint *ep)
> {
>     struct sock *sk;
> ...
>     kfree(ep);
>     SCTP_DBG_OBJCNT_DEC(ep);
> }
>
> The 'ep' object counter is being decremented?! Is the kfree to be there indeed?
> Let me know what was intended here.
>
> Same here:
> /net/sctp/endpointola.c (165)
> static void sctp_transport_destroy_rcu(struct rcu_head *head)
> {
>     struct sctp_transport *transport;
> ...
>     kfree(transport);
>     SCTP_DBG_OBJCNT_DEC(transport);
> }
>
> Regards,
>
> Geyslan Gregório Bem
> hackingbits.com

Oops. I got it. ;)

extern atomic_t sctp_dbg_objcnt_ep;
http://lxr.free-electrons.com/source/include/net/sctp/sctp.h#L269
extern atomic_t sctp_dbg_objcnt_transport;
http://lxr.free-electrons.com/source/arch/x86/include/asm/atomic.h#L105

Cheers.
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