Re: bug in generic_access_phys (mm/memory.c) ?

Paolo Minazzi
2013-10-29T10:47:00Z

Il 29/10/2013 9.44, Paolo Minazzi ha scritto:
> 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

This is a more simple patch in the usual diff format:

diff -r 6321bc9c43db linux-2.6.31.8/mm/memory.c
--- a/linux-2.6.31.8/mm/memory.c Tue Oct 22 13:35:14 2013 +0200
+++ b/linux-2.6.31.8/mm/memory.c Tue Oct 29 11:44:51 2013 +0100
@@ -3264,1 +3264,1 @@
- maddr = ioremap_prot(phys_addr, PAGE_SIZE);
+ maddr = ioremap_prot(phys_addr, ((offset + len - 1) &
~(PAGE_SIZE-1)) + PAGE_SIZE );

Regards,
Paolo Minazzi