From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
Courtney Cavin <courtney.cavin@sonymobile.com>
Subject: Re: Preemptible idr_alloc() in QRTR code
Date: Tue, 26 Jan 2021 11:00:05 -0600 [thread overview]
Message-ID: <YBBKla3I2TxMFIvZ@builder.lan> (raw)
In-Reply-To: <20210126162154.GD80448@C02TD0UTHF1T.local>
On Tue 26 Jan 10:21 CST 2021, Mark Rutland wrote:
> On Tue, Jan 26, 2021 at 02:58:33PM +0000, Matthew Wilcox wrote:
> > On Tue, Jan 26, 2021 at 10:47:34AM +0000, Mark Rutland wrote:
> > > Hi,
> > >
> > > When fuzzing arm64 with Syzkaller, I'm seeing some splats where
> > > this_cpu_ptr() is used in the bowels of idr_alloc(), by way of
> > > radix_tree_node_alloc(), in a preemptible context:
> >
> > I sent a patch to fix this last June. The maintainer seems to be
> > under the impression that I care an awful lot more about their
> > code than I do.
> >
> > https://lore.kernel.org/netdev/20200605120037.17427-1-willy@infradead.org/
>
> Ah; I hadn't spotted the (glaringly obvious) GFP_ATOMIC abuse, thanks
> for the pointer, and sorry for the noise.
>
I'm afraid this isn't as obvious to me as it is to you. Are you saying
that one must not use GFP_ATOMIC in non-atomic contexts?
That said, glancing at the code I'm puzzled to why it would use
GFP_ATOMIC.
> It looks like Eric was after a fix that trivially backported to v4.7
> (and hence couldn't rely on xarray) but instead it just got left broken
> for months. :/
>
> Bjorn, is this something you care about? You seem to have the most
> commits to the file, and otherwise the official maintainer is Dave
> Miller per get_maintainer.pl.
>
I certainly care about qrtr working and remember glancing at Matthew's
patch, but seems like I never found time to properly review it.
> It is very tempting to make the config option depend on BROKEN...
>
I hear you and that would be bad, so I'll make sure to take a proper
look at this and Matthew's patch.
Thanks,
Bjorn
next prev parent reply other threads:[~2021-01-27 0:20 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-26 10:47 Preemptible idr_alloc() in QRTR code Mark Rutland
2021-01-26 14:58 ` Matthew Wilcox
2021-01-26 16:21 ` Mark Rutland
2021-01-26 17:00 ` Bjorn Andersson [this message]
2021-01-26 18:36 ` Mark Rutland
2021-01-27 0:41 ` Matthew Wilcox
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