linux-kernel - Re: [PATCH] x86/PCI: fix a memory leak bug

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Date:   Tue, 16 Apr 2019 08:37:27 -0500
From:   Wenwen Wang <wang6495@....edu>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
        "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" 
        <linux-kernel@...r.kernel.org>, Wenwen Wang <wang6495@....edu>
Subject: Re: [PATCH] x86/PCI: fix a memory leak bug

On Tue, Apr 16, 2019 at 2:23 AM Ingo Molnar <mingo@...nel.org> wrote:
>
>
> * Wenwen Wang <wang6495@....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@....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'?
>

Thanks for your comment! I will rework the patch.

Wenwen

> >       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@...nel.org>
>
> Thanks,
>
>         Ingo