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Date:   Tue, 16 Apr 2019 09:23:27 +0200
From:   Ingo Molnar <mingo@kernel.org>
To:     Wenwen Wang <wang6495@umn.edu>
Cc:     Bjorn Helgaas <bhelgaas@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@kernel.org>,
        "open list:PCI SUBSYSTEM" <linux-pci@vger.kernel.org>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86/PCI: fix a memory leak bug
Message-ID: <20190416072327.GA127769@gmail.com>
References: <1555340058-3065-1-git-send-email-wang6495@umn.edu>
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* Wenwen Wang <wang6495@umn.edu> wrote:

> In pcibios_irq_init(), the PCI IRQ routing table 'pirq_table' is firstly
> found through pirq_find_routing_table(). If the table is not found and
> 'CONFIG_PCI_BIOS' is defined, the table is then allocated in
> pcibios_get_irq_routing_table() using kmalloc(). In the following
> execution, if the I/O APIC is used, this table is actually not used.
> However, in that case, the allocated table is not freed, which can lead to
> a memory leak bug.
> 
> To fix this issue, this patch frees the allocated table if it is not used.
> 
> Signed-off-by: Wenwen Wang <wang6495@umn.edu>
> ---
>  arch/x86/pci/irq.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/pci/irq.c b/arch/x86/pci/irq.c
> index 52e5510..d9bcb96 100644
> --- a/arch/x86/pci/irq.c
> +++ b/arch/x86/pci/irq.c
> @@ -1119,6 +1119,8 @@ static const struct dmi_system_id pciirq_dmi_table[] __initconst = {
>  
>  void __init pcibios_irq_init(void)
>  {
> +	struct irq_routing_table *itable = NULL;
> +

Minor style nit: the canonical name of irq_routing_table local variables 
is usually 'rtable' or 'rt' - let's not add a third naming variant with 
'itable'?

>  	DBG(KERN_DEBUG "PCI: IRQ init\n");
>  
>  	if (raw_pci_ops == NULL)
> @@ -1129,8 +1131,10 @@ void __init pcibios_irq_init(void)
>  	pirq_table = pirq_find_routing_table();
>  
>  #ifdef CONFIG_PCI_BIOS
> -	if (!pirq_table && (pci_probe & PCI_BIOS_IRQ_SCAN))
> +	if (!pirq_table && (pci_probe & PCI_BIOS_IRQ_SCAN)) {
>  		pirq_table = pcibios_get_irq_routing_table();
> +		itable = pirq_table;
> +	}
>  #endif
>  	if (pirq_table) {
>  		pirq_peer_trick();
> @@ -1145,8 +1149,10 @@ void __init pcibios_irq_init(void)
>  		 * If we're using the I/O APIC, avoid using the PCI IRQ
>  		 * routing table
>  		 */
> -		if (io_apic_assign_pci_irqs)
> +		if (io_apic_assign_pci_irqs) {
> +			kfree(itable);
>  			pirq_table = NULL;
> +		}

Reviewed-by: Ingo Molnar <mingo@kernel.org>

Thanks,

	Ingo