Xen devel - May 2007 - [PATCH][HVM] HVM guest creation crashing with 1 MB of guest memory

Hi,

When an HVM guest is started and assigned exactly one Megabyte of RAM, 
XEN will crash due to a overflow in building the E820 map in line 90 of 
tools/libxc/xc_hvm_build.c:
e820entry[nr_map].size = mem_size - 0x100000 - PAGE_SIZE * 3;
If memsize is one MB, the result will be negative (and the member is 
unsigned). As I don''t think this is worth fixing here, I simply 
increased the minimal required memory for guest from zero to one 
Megabyte. Could someone check the effect on paravirtualized guests?

Regards,
Andre.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>

--
Andre Przywara
AMD-Operating System Research Center (OSRC), Dresden, Germany

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vertretungsberechtigter Komplementär: AMD Saxony LLC (Sitz Wilmington, 
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On 4/5/07 14:47, "Andre Przywara" <andre.przywara@amd.com>
wrote:
> When an HVM guest is started and assigned exactly one Megabyte of RAM,
> XEN will crash due to a overflow in building the E820 map in line 90 of
> tools/libxc/xc_hvm_build.c:
> e820entry[nr_map].size = mem_size - 0x100000 - PAGE_SIZE * 3;
> If memsize is one MB, the result will be negative (and the member is
> unsigned). As I don''t think this is worth fixing here, I simply
> increased the minimal required memory for guest from zero to one
> Megabyte. Could someone check the effect on paravirtualized guests?
Better to check and reject the memory size in xc_hvm_build() itself.
I''ll
make a patch to do this.

 -- Keir



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