Doubts about Patch "ipack/carriers/tpci200: Fix a double free in tpci200_pci_probe"

From: Dongliang Mu
Date: Tue Jul 20 2021 - 02:49:24 EST

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.

/* 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 *);
struct pci_dev;
static inline void pci_iounmap(struct pci_dev *dev, void __iomem *addr)
{ }

> 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