From: Herbert Xu <herbert@gondor.apana.org.au>
To: Greg Hackmann <ghackmann@google.com>
Cc: Steffen Klassert <steffen.klassert@secunet.com>,
"David S. Miller" <davem@davemloft.net>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 net] net: xfrm: use preempt-safe this_cpu_read() in ipcomp_alloc_tfms()
Date: Thu, 8 Mar 2018 16:23:12 +0800 [thread overview]
Message-ID: <20180308082312.GA8403@gondor.apana.org.au> (raw)
In-Reply-To: <20180307224253.152470-1-ghackmann@google.com>
On Wed, Mar 07, 2018 at 02:42:53PM -0800, Greg Hackmann wrote:
> f7c83bcbfaf5 ("net: xfrm: use __this_cpu_read per-cpu helper") added a
> __this_cpu_read() call inside ipcomp_alloc_tfms().
>
> At the time, __this_cpu_read() required the caller to either not care
> about races or to handle preemption/interrupt issues. 3.15 tightened
> the rules around some per-cpu operations, and now __this_cpu_read()
> should never be used in a preemptible context. On 3.15 and later, we
> need to use this_cpu_read() instead.
>
> syzkaller reported this leading to the following kernel BUG while
> fuzzing sendmsg:
Please explain why we can't revert f7c83bcbfaf5 instead.
Your patch contradicts the comment above the line that you're
changing.
Thanks,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
next prev parent reply other threads:[~2018-03-08 8:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-07 22:42 [PATCH v2 net] net: xfrm: use preempt-safe this_cpu_read() in ipcomp_alloc_tfms() Greg Hackmann
2018-03-08 8:23 ` Herbert Xu [this message]
2018-03-13 6:50 ` Steffen Klassert
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