lkml.org 
[lkml]   [2014]   [Oct]   [14]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] xen/setup: add paranoid index check and warning
On 14/10/14 02:19, Martin Kelly wrote:
> In a call to set_phys_range_identity, i-1 is used without checking that
> i is non-zero. Although unlikely, a bug in the code before it could
> cause the value to be 0, leading to erroneous behavior. This patch adds
> a check against 0 value and a corresponding warning.

This can only happen if the toolstack supplies a memory map with zero
entries. I could see justification for adding a panic at the top of
this function in this case, but I can't see the usefulness of this warning.

> --- a/arch/x86/xen/setup.c
> +++ b/arch/x86/xen/setup.c
> @@ -671,7 +671,10 @@ char * __init xen_memory_setup(void)
> * PFNs above MAX_P2M_PFN are considered identity mapped as
> * well.
> */
> - set_phys_range_identity(map[i-1].addr / PAGE_SIZE, ~0ul);
> + if (i > 0)
> + set_phys_range_identity(map[i-1].addr / PAGE_SIZE, ~0ul);
> + else
> + WARN(1, "Something went wrong clamping memory to a factor of EXTRA_MEM_RATIO!");
>
> /*
> * In domU, the ISA region is normal, usable memory, but we
>



\
 
 \ /
  Last update: 2014-10-14 12:01    [W:0.421 / U:0.028 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site