From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Hackmann Subject: Re: [PATCH] net: xfrm: use preempt-safe this_cpu_read() in ipcomp_alloc_tfms() Date: Wed, 7 Mar 2018 12:50:00 -0800 Message-ID: References: <20180307192416.233202-1-ghackmann@google.com> <1520454081.109662.54.camel@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Eric Dumazet , Steffen Klassert , Herbert Xu , "David S. Miller" Return-path: In-Reply-To: <1520454081.109662.54.camel@gmail.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 03/07/2018 12:21 PM, Eric Dumazet wrote: > On Wed, 2018-03-07 at 11:24 -0800, Greg Hackmann wrote: >> f7c83bcbfaf5 ("net: xfrm: use __this_cpu_read per-cpu helper") added >> a >> __this_cpu_read() call inside ipcomp_alloc_tfms().  Since this call >> was >> introduced, the rules around per-cpu accessors have been tightened >> and >> __this_cpu_read() cannot be used in a preemptible context. >> >> syzkaller reported this leading to the following kernel BUG while >> fuzzing sendmsg: >> >> >> Cc: stable@vger.kernel.org > > Hi Greg, thanks for this patch. > > 1) Please read Documentation/networking/netdev-FAQ.txt > around line 133 > > 2) If you believe this needs to be backported, you must provide > a Fixes: tag to clearly identify commit that changed the behavior. > > Otherwise dozens of stable teams will have to figure out by themselves, > wasting precious time. > > Thanks. > Apologies, I forgot that netdev has its own stable rules. I'll double-check which kernels are impacted and resend with an updated commit log.