Re: [PATCH] irqchip/aspeed-i2c-ic: Fix irq domain name memory leak

From: Marc Zyngier <maz@kernel.org>
To: "Andrew Jeffery" <andrew@aj.id.au>
Cc: "Roy van Doormaal" <roy.van.doormaal@prodrive-technologies.com>,
	"Brendan Higgins" <brendanhiggins@google.com>,
	"Benjamin Herrenschmidt" <benh@kernel.crashing.org>,
	"Joel Stanley" <joel@jms.id.au>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Jason Cooper" <jason@lakedaemon.net>,
	linux-i2c@vger.kernel.org, openbmc@lists.ozlabs.org,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-aspeed@lists.ozlabs.org
Subject: Re: [PATCH] irqchip/aspeed-i2c-ic: Fix irq domain name memory leak
Date: Tue, 26 Nov 2019 04:45:33 +0000	[thread overview]
Message-ID: <20191126044533.20d84e37@why> (raw)
In-Reply-To: <ff44cecd-7e05-4e5d-b88f-2d6af6fd8b8b@www.fastmail.com>

On Tue, 26 Nov 2019 10:08:36 +1030
"Andrew Jeffery" <andrew@aj.id.au> wrote:

> On Tue, 26 Nov 2019, at 06:59, Roy van Doormaal wrote:
> > The aspeed irqchip driver overwrites the default irq domain name,
> > but doesn't free the existing domain name.
> > This patch frees the irq domain name before overwriting it.
> > 
> > kmemleak trace:
> > 
> > unreferenced object 0xb8004c40 (size 64):
> > comm "swapper", pid 0, jiffies 4294937303 (age 747.660s)
> > hex dump (first 32 bytes):
> > 3a 61 68 62 3a 61 70 62 3a 62 75 73 40 31 65 37 :ahb:apb:bus@1e7
> > 38 61 30 30 30 3a 69 6e 74 65 72 72 75 70 74 2d 8a000:interrupt-
> > backtrace:
> > [<086b59b8>] kmemleak_alloc+0xa8/0xc0
> > [<b5a3490c>] __kmalloc_track_caller+0x118/0x1a0
> > [<f59c7ced>] kvasprintf+0x5c/0xc0
> > [<49275eec>] kasprintf+0x30/0x50
> > [<5713064b>] __irq_domain_add+0x184/0x25c
> > [<53c594d0>] aspeed_i2c_ic_of_init+0x9c/0x128
> > [<d8d7017e>] of_irq_init+0x1ec/0x314
> > [<f8405bf1>] irqchip_init+0x1c/0x24
> > [<7ef974b3>] init_IRQ+0x30/0x90
> > [<87a1438f>] start_kernel+0x28c/0x458
> > [< (null)>] (null)
> > [<f0763fdf>] 0xffffffff
> > 
> > Signed-off-by: Roy van Doormaal <roy.van.doormaal@prodrive-technologies.com>
> > ---
> >  drivers/irqchip/irq-aspeed-i2c-ic.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/drivers/irqchip/irq-aspeed-i2c-ic.c 
> > b/drivers/irqchip/irq-aspeed-i2c-ic.c
> > index 8d591c179f81..8081b8483a79 100644
> > --- a/drivers/irqchip/irq-aspeed-i2c-ic.c
> > +++ b/drivers/irqchip/irq-aspeed-i2c-ic.c
> > @@ -92,6 +92,8 @@ static int __init aspeed_i2c_ic_of_init(struct 
> > device_node *node,
> >  		goto err_iounmap;
> >  	}
> >  
> > +	if (i2c_ic->irq_domain->flags & IRQ_DOMAIN_NAME_ALLOCATED)
> > +		kfree(i2c_ic->irq_domain->name);
> >  	i2c_ic->irq_domain->name = "aspeed-i2c-domain";  
> 
> Given that the name is no-longer allocated I think you need to clear the
> IRQ_DOMAIN_NAME_ALLOCATED bit from flags to avoid attempting to
> free the const string in irq_domain_remove():
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/irq/irqdomain.c?h=v5.4#n263
> 
> Or do a kstrdup().

Or even better, drop the whole domain name assignment, which is pretty
pointless and makes debugging pointlessly difficult (see how the name
is used to build the irq debugfs).

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...