linux-kernel - Re: linuxnext-2019127 edac warns (was Re: edac KASAN warning in experimental arm64 allmodconfig boot)

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Date:   Thu, 28 Nov 2019 21:12:47 +0000
From:   Robert Richter <rrichter@...vell.com>
To:     John Garry <john.garry@...wei.com>
CC:     Borislav Petkov <bp@...en8.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        James Morse <james.morse@....com>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        wanghuiqiang <wanghuiqiang@...wei.com>,
        Xiaofei Tan <tanxiaofei@...wei.com>,
        Linuxarm <linuxarm@...wei.com>,
        "Huangming (Mark)" <huangming23@...wei.com>
Subject: Re: linuxnext-2019127 edac warns (was Re: edac KASAN warning in
 experimental arm64 allmodconfig boot)

On 27.11.19 17:07:33, John Garry wrote:
> [   22.104498] BUG: KASAN: use-after-free in
> edac_remove_sysfs_mci_device+0x148/0x180

It is triggered in edac_remove_sysfs_mci_device().

device_unregister(&dimm->dev) not only removes the sysfs entry, it
also frees the dimm struct in dimm_attr_release(). When incrementing
the loop in mci_for_each_dimm(), the dimm struct is accessed again
which causes the use-after-free. But, the dimm struct shouln'd be
released here already.

edac_remove_sysfs_mci_device() should not release the devices at this
point. We need clean release functions for mci and dimm_info and
refcounts to protect pdev/dev mappings. And mci_for_each_dimm() must
be checked how it handles device removals and if it is safe.

Let's see how this can be fixed.

Thanks for reporting the issue.

-Robert