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Date: Thu, 14 Mar 2019 05:58:03 -0700 From: Eric Dumazet <eric.dumazet@...il.com> To: Sabrina Dubroca <sd@...asysnail.net>, netdev@...r.kernel.org Cc: Eric Dumazet <eric.dumazet@...il.com>, Jianlin Shi <jishi@...hat.com>, Stefano Brivio <sbrivio@...hat.com> Subject: Re: [PATCH net] net: enforce xmit_recursion for devices with a queue On 03/14/2019 03:15 AM, Sabrina Dubroca wrote: > Commit 745e20f1b626 ("net: add a recursion limit in xmit path") > introduced a recursion limit, but it only applies to devices without a > queue. Virtual devices with a queue (either because they don't have > the IFF_NO_QUEUE flag, or because the administrator added one) can > still cause an unbounded recursion, via __dev_queue_xmit -> > __dev_xmit_skb -> qdisc_run -> __qdisc_run -> qdisc_restart -> > sch_direct_xmit -> dev_hard_start_xmit . Jianlin reported this in a > setup with 16 gretap devices stacked on top of one another. > > This patch prevents the stack overflow by incrementing xmit_recursion in > code paths that can call dev_hard_start_xmit() (like commit 745e20f1b626 > did). If the recursion limit is exceeded, the packet is enqueued and the > qdisc is scheduled. > > Reported-by: Jianlin Shi <jishi@...hat.com> > Signed-off-by: Sabrina Dubroca <sd@...asysnail.net> > Reviewed-by: Stefano Brivio <sbrivio@...hat.com> Hi Sabrina, thanks for the patch. Can't we detect this in the control path instead ? Surely this makes no sense in real world to stack 16 devices like that.
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