Xen devel - Nov 2013 - [PATCH V3] xen: Check if the range is valid in init_domheap_pages

On ARM, when an initrd is given to xen by U-boot, it will reserve the memory in
the device tree.
In this case, when xen decides to free unused memory, dt_unreserved_regions
will call init_domheap_pages with the start and the end of range equals. But
the latter assumes that (start > end), if not Xen will hang because the
number of pages is equals to (unsigned)-1.

Signed-off-by: Julien Grall <julien.grall@linaro.org>
CC: Keir Fraser <keir@xen.org>
CC: Jan Beulich <jbeulich@suse.com>

---
    Changes in v3:
        - Invert the check

    Changes in v2:
        - Change commit title
        - Move the check in init_domheap_pages
---
 xen/common/page_alloc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 4c17fbd..0701333 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -1429,6 +1429,9 @@ void init_domheap_pages(paddr_t ps, paddr_t pe)
     smfn = round_pgup(ps) >> PAGE_SHIFT;
     emfn = round_pgdown(pe) >> PAGE_SHIFT;
 
+    if ( emfn <= smfn )
+        return;
+
     init_heap_pages(mfn_to_page(smfn), emfn - smfn);
 }
 
-- 
1.8.3.1

On 13/11/2013 13:37, "Julien Grall" <julien.grall@linaro.org>
wrote:
> On ARM, when an initrd is given to xen by U-boot, it will reserve the
memory
> in
> the device tree.
> In this case, when xen decides to free unused memory, dt_unreserved_regions
> will call init_domheap_pages with the start and the end of range equals.
But
> the latter assumes that (start > end), if not Xen will hang because the
> number of pages is equals to (unsigned)-1.
> 
> Signed-off-by: Julien Grall <julien.grall@linaro.org>
> CC: Keir Fraser <keir@xen.org>
> CC: Jan Beulich <jbeulich@suse.com>
I understand Jan''s reservations, but I think just being more liberal
here is
fine really.

Acked-by: Keir Fraser <keir@xen.org>

On 11/13/2013 01:37 PM, Julien Grall wrote:
> On ARM, when an initrd is given to xen by U-boot, it will reserve the
memory in
> the device tree.
> In this case, when xen decides to free unused memory, dt_unreserved_regions
> will call init_domheap_pages with the start and the end of range equals.
But
> the latter assumes that (start > end), if not Xen will hang because the
> number of pages is equals to (unsigned)-1.
> 
> Signed-off-by: Julien Grall <julien.grall@linaro.org>
> CC: Keir Fraser <keir@xen.org>
> CC: Jan Beulich <jbeulich@suse.com>
Ping ? Without this commit, the user is unable to pass initrd to dom0 on
ARM.

-- 
Julien Grall

On 20/11/2013 08:09, "Julien Grall" <julien.grall@citrix.com>
wrote:
> On 11/13/2013 01:37 PM, Julien Grall wrote:
>> On ARM, when an initrd is given to xen by U-boot, it will reserve the
memory
>> in
>> the device tree.
>> In this case, when xen decides to free unused memory,
dt_unreserved_regions
>> will call init_domheap_pages with the start and the end of range
equals. But
>> the latter assumes that (start > end), if not Xen will hang because
the
>> number of pages is equals to (unsigned)-1.
>> 
>> Signed-off-by: Julien Grall <julien.grall@linaro.org>
>> CC: Keir Fraser <keir@xen.org>
>> CC: Jan Beulich <jbeulich@suse.com>
> 
> Ping ? Without this commit, the user is unable to pass initrd to dom0 on
> ARM.
It was fine with me.

Acked-by: Keir Fraser <keir@xen.org>