From: Borislav Petkov <bp@alien8.de>
To: James Morse <james.morse@arm.com>
Cc: linux-edac@vger.kernel.org,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Tony Luck <tony.luck@intel.com>,
Robert Richter <rrichter@marvell.com>,
John Garry <john.garry@huawei.com>
Subject: Re: [PATCH 0/2] EDAC, ghes: Fix use after free and add reference
Date: Tue, 15 Oct 2019 15:25:49 +0200 [thread overview]
Message-ID: <20191015132549.GC596@zn.tnic> (raw)
In-Reply-To: <20191014171919.85044-1-james.morse@arm.com>
On Mon, Oct 14, 2019 at 06:19:17PM +0100, James Morse wrote:
> Hello,
>
> ghes_edac can only be registered once, later attempts will silently
> do nothing as the driver is already setup. The unregister path also
> only expects to be called once, but doesn't check.
>
> This leads to KASAN splats if multiple GHES entries are unregistered,
> as the free()d memory is dereferenced, and if we're lucky, free()d
> a second time.
>
> Link: lore.kernel.org/r/304df85b-8b56-b77e-1a11-aa23769f2e7c@huawei.com
>
> Patch 1 is the minimum needed to prevent the dereference and double
> free, but this does expose the lack of symmetry. If we unregister
> one GHES entry, subsequent notifications will be lost.
> Unregistering is unsafe if another CPU is using the free()d memory in
> ghes_edac_report_mem_error().
>
> To fix this, Patch 2 uses ghes_init as a reference count.
>
> We can now unbind all the GHES entries, causing ghes_edac to be
> unregistered, and start rebinding them again.
>
>
> Thanks,
>
> James Morse (2):
> EDAC, ghes: Fix Use after free in ghes_edac remove path
> EDAC, ghes: Reference count GHES users of ghes_edac
>
> drivers/edac/ghes_edac.c | 4 ++++
> 1 file changed, 4 insertions(+)
Patches squashed and queued here:
https://git.kernel.org/pub/scm/linux/kernel/git/ras/ras.git/log/?h=edac-urgent
Will send it to Linus soonish as it is stable material, I guess.
In the meantime, we can iron the whole deal out and improve it.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
prev parent reply other threads:[~2019-10-15 13:25 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-14 17:19 [PATCH 0/2] EDAC, ghes: Fix use after free and add reference James Morse
2019-10-14 17:19 ` [PATCH 1/2] EDAC, ghes: Fix Use after free in ghes_edac remove path James Morse
2019-10-14 17:19 ` [PATCH 2/2] EDAC, ghes: Reference count GHES users of ghes_edac James Morse
2019-10-14 17:30 ` [PATCH 0/2] EDAC, ghes: Fix use after free and add reference Borislav Petkov
2019-10-14 17:40 ` James Morse
2019-10-14 17:53 ` Borislav Petkov
2019-10-16 15:17 ` Borislav Petkov
2019-10-16 15:30 ` James Morse
2019-10-16 18:50 ` Borislav Petkov
2019-10-21 7:37 ` Borislav Petkov
2019-10-21 10:52 ` Robert Richter
2019-10-22 13:25 ` Robert Richter
2019-10-15 13:25 ` Borislav Petkov [this message]
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