Just nitpicks:
On Wed, Apr 10, 2013 at 04:32:52PM -0700, Dave Hansen wrote:
>
> I was auding the /dev/mem code for more questionable uses of
auditing
> __pa(), and ran across this.
>
> My assumption is that if you use /dev/kmem, you expect to be
> able to read the kernel virtual mappings. However, those
> mappings _stop_ as soon as we hit high memory. The
> pfn_valid() check in here is good for memory holes, but since
> highmem pages are still valid, it does no good for those.
>
> Also, since we are now checking that __pa() is being done on
> valid virtual addresses, this might have tripped the new
> check. Even with the new check, this code would have been
> broken with the NUMA remapping code had we not ripped it
> out:
>
> https://patchwork.kernel.org/patch/2075911/
This is an upstream commit so you probably might want to state the
commit id here instead of some website which may or may not exist in the
future.
> Signed-off-by: Dave Hansen <d...@linux.vnet.ibm.com>
> Signed-off-by: Dave Hansen <dave.han...@linux.intel.com>
> ---
>
> linux.git-davehans/drivers/char/mem.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff -puN drivers/char/mem.c~make-kmem-return-error-for-highmem
> drivers/char/mem.c
> --- linux.git/drivers/char/mem.c~make-kmem-return-error-for-highmem
> 2013-04-10 16:23:45.151087081 -0700
> +++ linux.git-davehans/drivers/char/mem.c 2013-04-10 16:23:45.154087084
> -0700
> @@ -336,10 +336,19 @@ static int mmap_mem(struct file *file, s
> #ifdef CONFIG_DEVKMEM
> static int mmap_kmem(struct file *file, struct vm_area_struct *vma)
> {
> + unsigned long kernel_vaddr;
> unsigned long pfn;
>
> + kernel_vaddr = (u64)vma->vm_pgoff << PAGE_SHIFT;
> + /*
> + * pfn_valid() (below) does not trip for highmem addresses. This
> + * essentially means that we will be mapping gibberish in for them
> + * instead of what the _kernel_ has mapped at the requested address.
> + */
> + if (kernel_vaddr >= high_memory)
> + return -EIO;
drivers/char/mem.c: In function ‘mmap_kmem’:
drivers/char/mem.c:348:19: warning: comparison between pointer and integer
[enabled by default]
> /* Turn a kernel-virtual address into a physical page frame */
> - pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;
> + pfn = __pa(kernel_vaddr) >> PAGE_SHIFT;
>
> /*
> * RED-PEN: on some architectures there is more mapped memory than
> _
>
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
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