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SubjectRe: [PATCH] resource: make sure requested range intersects root range
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On Wed, Jul 11, 2012 at 5:54 PM, Ram Pai <linuxram@us.ibm.com> wrote:
> On Wed, Jul 11, 2012 at 02:06:10PM +0300, Purdila, Octavian wrote:
>> On Wed, Jul 11, 2012 at 5:09 AM, Ram Pai <linuxram@us.ibm.com> wrote:
>>
>> >
>> > Wait.. I am not sure this will fix the problem entirely. The above check
>> > will handle the case where the range requested is entirey out of the
>> > root's range. But if the requested range overlapps that of the root
>> > range, we will still call __reserve_region_with_split() and end up with
>> > a recursion if there is a overflow. Wont we?
>> >
>>
>> Good catch. I will fix this as well as address Andrew's and Joe's
>> comments in a new patch. The only question is how to handle the
>> overlap case:
>>
>> (a) abort the whole request or
>>
>> (b) try to reserve the part that overlaps (and adjust the request to
>> avoid the overflow)
>>
>> I think (b) is more in line with the current implementation for reservations.
>
>
> I prefer (b). following patch should handle that.
>
> diff --git a/kernel/resource.c b/kernel/resource.c
> index e1d2b8e..dd87fde 100644
> --- a/kernel/resource.c
> +++ b/kernel/resource.c
> @@ -780,6 +780,10 @@ static void __init __reserve_region_with_split(struct resource *root,
>
> if (conflict->start > start)
> __reserve_region_with_split(root, start, conflict->start-1, name);
> +
> + if (conflict->end == parent->end )
> + return;
> +
> if (conflict->end < end)
> __reserve_region_with_split(root, conflict->end+1, end, name);
> }
>

I don't think this covers all cases, e.g. if root range starts
somewhere above 0 and the request is below the root start point.

What about something like below? It is maybe too verbose, but it
should make it easier to find the offender.

diff --git a/kernel/resource.c b/kernel/resource.c
index e1d2b8e..0d71983 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -788,8 +788,29 @@ void __init reserve_region_with_split(struct
resource *root,
resource_size_t start, resource_size_t end,
const char *name)
{
+ int abort = 0;
+
write_lock(&resource_lock);
- __reserve_region_with_split(root, start, end, name);
+ if (!(root->start >= start && root->end >= end)) {
+ pr_err("Requested range (0x%llx-0x%llx) not in root %pr\n",
+ (unsigned long long)start, (unsigned long long)end,
+ root);
+ if (start > root->end || end < root->start) {
+ abort = 1;
+ pr_err("Unable to fix request, aborting\n");
+ } else {
+ if (end > root->end)
+ end = root->end;
+ else if (start < root->start)
+ start = root->start;
+ pr_err("Request trimmed to (0x%llx-0x%llx)\n",
+ (unsigned long long)start,
+ (unsigned long long)end);
+ }
+ dump_stack();
+ }
+ if (!abort)
+ __reserve_region_with_split(root, start, end, name);
write_unlock(&resource_lock);
}

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