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From:   Dongliang Mu <mudongliangabcd@gmail.com>
Date:   Tue, 20 Jul 2021 14:47:23 +0800
Message-ID: <CAD-N9QVFnhKGfRYDDjWb0o_ty57AbjfzEnFPHZxEC5NOKL1ecg@mail.gmail.com>
Subject: Doubts about Patch "ipack/carriers/tpci200: Fix a double free in tpci200_pci_probe"
To:     lyl2019@mail.ustc.edu.cn, siglesias@igalia.com,
        jens.taprogge@taprogge.org, Greg KH <gregkh@linuxfoundation.org>
Cc:     industrypack-devel@lists.sourceforge.net,
        linux-kernel <linux-kernel@vger.kernel.org>
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Hi all,

I have some doubts about the patch - "ipack/carriers/tpci200: Fix a
double free in tpci200_pci_probe".

> In the out_err_bus_register error branch of tpci200_pci_probe,
> tpci200->info->cfg_regs is freed by tpci200_uninstall()->
> tpci200_unregister()->pci_iounmap(..,tpci200->info->cfg_regs)
> in the first time.

From my code review, although pci_iounmap takes
"tpci200->info->cfg_regs" as its 2nd parameter, the implementation of
pci_iounmap may not use this parameter.

 Depending on if CONFIG_PCI defines, the "tpci200->info->cfg_regs" may
not be freed.

#ifdef CONFIG_PCI
/* Destroy a virtual mapping cookie for a PCI BAR (memory or IO) */
struct pci_dev;
extern void pci_iounmap(struct pci_dev *dev, void __iomem *);
#elif defined(CONFIG_GENERIC_IOMAP)
struct pci_dev;
static inline void pci_iounmap(struct pci_dev *dev, void __iomem *addr)
{ }
#endif

> But later, iounmap() is called to free tpci200->info->cfg_regs again.

Even if CONFIG_PCI is undefined, it is possible that
tpci200->info->cfg_regs is not freed at all. Therefore, this patch
would cause memory leak. Take a look at the following code:

void pci_iounmap(struct pci_dev *dev, void __iomem * addr)
{
        IO_COND(addr, /* nothing */, iounmap(addr));
}

#define IO_COND(addr, is_pio, is_mmio) do {                     \
        unsigned long port = (unsigned long __force)addr;       \
        if (port >= PIO_RESERVED) {                             \
                is_mmio;                                        \
        } else if (port > PIO_OFFSET) {                         \
                port &= PIO_MASK;                               \
                is_pio;                                         \
        } else                                                  \
                bad_io_access(port, #is_pio );                  \
} while (0)

If I make any mistakes, please let me know.

--
My best regards to you.

     No System Is Safe!
     Dongliang Mu