bug in generic_access_phys (mm/memory.c) ?

Paolo Minazzi
2013-10-29T08:53:49Z

Hi to all,
I think the function "generic_access_phys" in mm/memory.c has got a
small bug.
THe ioremap_prot is called with the parameter size=PAGE_SIZE.
But it can happen that we need more than one page, and this will produce
a kernel fault.

int generic_access_phys(struct vm_area_struct *vma, unsigned long addr,
void *buf, int len, int write)
{
resource_size_t phys_addr;
unsigned long prot = 0;
void __iomem *maddr;
int offset = addr & (PAGE_SIZE-1);

if (follow_phys(vma, addr, write, &prot, &phys_addr))
return -EINVAL;

====> maddr = ioremap_prot(phys_addr, PAGE_SIZE);

if (write)
memcpy_toio(maddr + offset, buf, len);
else
memcpy_fromio(buf, maddr + offset, len);
iounmap(maddr);

return len;
}

I think that the ioremap_prot should be changed with

maddr = ioremap_prot(phys_addr, ((phys_addr + offset + len - 1) &
~(PAGE_SIZE-1)) -
phys_addr + PAGE_SIZE);

Thanks,
Paolo Minazzi