From: Borislav Petkov <bp@alien8.de>
To: Robert Richter <rrichter@marvell.com>
Cc: "john.garry@huawei.com" <john.garry@huawei.com>,
Mauro Carvalho Chehab <mchehab@kernel.org>,
Tony Luck <tony.luck@intel.com>,
"huangming23@huawei.com" <huangming23@huawei.com>,
"james.morse@arm.com" <james.morse@arm.com>,
"linux-edac@vger.kernel.org" <linux-edac@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linuxarm@huawei.com" <linuxarm@huawei.com>,
"tanxiaofei@huawei.com" <tanxiaofei@huawei.com>,
"wanghuiqiang@huawei.com" <wanghuiqiang@huawei.com>
Subject: Re: [PATCH] EDAC/ghes: Do not warn when incrementing refcount on 0
Date: Fri, 22 Nov 2019 10:01:23 +0100 [thread overview]
Message-ID: <20191122090123.GB6289@zn.tnic> (raw)
In-Reply-To: <20191121213628.21244-1-rrichter@marvell.com>
On Thu, Nov 21, 2019 at 09:36:57PM +0000, Robert Richter wrote:
> Following warning from the refcount framework is seen during ghes
> initialization:
>
> EDAC MC0: Giving out device to module ghes_edac.c controller ghes_edac: DEV ghes (INTERRUPT)
> ------------[ cut here ]------------
> refcount_t: increment on 0; use-after-free.
> WARNING: CPU: 36 PID: 1 at lib/refcount.c:156 refcount_inc_checked+0x44/0x50
> [...]
> Call trace:
> refcount_inc_checked+0x44/0x50
> ghes_edac_register+0x258/0x388
> ghes_probe+0x28c/0x5f0
>
> It warns if the refcount is incremented from zero. This warning is
> reasonable as a kernel object is typically created with a refcount of
> one and freed once the refcount is zero. Afterwards the object would
> be "used-after-free".
>
> For ghes the refcount is initialized with zero, and that is why this
> message is seen when initializing the first instance. However,
> whenever the refcount is zero, the device will be allocated and
> registered. Since the ghes_reg_mutex protects the refcount and
> serializes allocation and freeing of ghes devices, a use-after-free
> cannot happen here.
>
> Instead of using refcount_inc() for the first instance, use
> refcount_set(). This can be used here because the refcount is zero at
> this point and can not change due to its protection by the mutex.
>
> Reported-by: John Garry <john.garry@huawei.com>
> Tested-by: John Garry <john.garry@huawei.com>
> Signed-off-by: Robert Richter <rrichter@marvell.com>
> ---
> drivers/edac/ghes_edac.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
Queued, thanks.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2019-11-22 9:01 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-14 15:18 edac KASAN warning in experimental arm64 allmodconfig boot John Garry
2019-10-14 16:09 ` Borislav Petkov
2019-10-14 16:44 ` John Garry
2019-10-14 16:15 ` James Morse
2019-10-14 16:56 ` John Garry
2019-10-14 16:57 ` Borislav Petkov
2019-11-21 12:34 ` linuxnext-2019119 edac warns (was Re: edac KASAN warning in experimental arm64 allmodconfig boot) John Garry
2019-11-21 14:23 ` Robert Richter
2019-11-21 15:23 ` John Garry
2019-11-21 21:36 ` [PATCH] EDAC/ghes: Do not warn when incrementing refcount on 0 Robert Richter
2019-11-22 9:01 ` Borislav Petkov [this message]
2019-11-26 9:57 ` John Garry
2019-11-22 11:28 ` linuxnext-2019119 edac warns (was Re: edac KASAN warning in experimental arm64 allmodconfig boot) Robert Richter
2019-11-26 9:59 ` John Garry
2019-11-27 17:07 ` linuxnext-2019127 " John Garry
2019-11-27 20:54 ` Robert Richter
2019-11-28 11:02 ` linuxnext-20191127 " John Garry
2019-11-28 16:44 ` Borislav Petkov
2019-11-28 21:12 ` linuxnext-2019127 " Robert Richter
2019-12-02 10:23 ` John Garry
2019-12-02 11:46 ` Robert Richter
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