linux-kernel - Re: [PATCH] net: xfrm: use preempt-safe this_cpu_read() in ipcomp_alloc

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Message-ID: <20180308073328.GA8111@gondor.apana.org.au>
Date:   Thu, 8 Mar 2018 15:33:28 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Greg Hackmann <ghackmann@...gle.com>
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] net: xfrm: use preempt-safe this_cpu_read() in
 ipcomp_alloc_tfms()

On Wed, Mar 07, 2018 at 11:24:16AM -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:

How about reverting f7c83bcbfaf5 instead?

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt