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

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Message-Id: <ff44cecd-7e05-4e5d-b88f-2d6af6fd8b8b@www.fastmail.com>
Date:   Tue, 26 Nov 2019 10:08:36 +1030
From:   "Andrew Jeffery" <andrew@...id.au>
To:     "Roy van Doormaal" <roy.van.doormaal@...drive-technologies.com>,
        "Brendan Higgins" <brendanhiggins@...gle.com>,
        "Benjamin Herrenschmidt" <benh@...nel.crashing.org>,
        "Joel Stanley" <joel@....id.au>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Jason Cooper" <jason@...edaemon.net>,
        "Marc Zyngier" <maz@...nel.org>, linux-i2c@...r.kernel.org,
        openbmc@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-aspeed@...ts.ozlabs.org
Subject: Re: [PATCH] irqchip/aspeed-i2c-ic: Fix irq domain name memory leak



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@...drive-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().

Andrew