[PATCH v5 4/9] resources: handle overflow when aligning start of available area

Bjorn Helgaas
2010-10-26T21:41:32Z

If tmp.start is near ~0, ALIGN(tmp.start) may overflow, which would
make us think there's more available space than there really is. We
would likely return something that conflicts with a previous resource,
which would cause a failure when allocate_resource() requests the newly-
allocated region.

Reference: https://bugzilla.redhat.com/show_bug.cgi?id=646027
Reported-by: Fabrice Bellet <fabrice@bellet.info>
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
---

kernel/resource.c | 21 +++++++++++++--------
1 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/kernel/resource.c b/kernel/resource.c
index 89d5041..e15b922 100644
--- a/kernel/resource.c
+++ b/kernel/resource.c
@@ -392,7 +392,7 @@ static int find_resource(struct resource *root, struct resource *new,
void *alignf_data)
{
struct resource *this = root->child;
- struct resource tmp = *new, alloc;
+ struct resource tmp = *new, avail, alloc;

tmp.start = root->start;
/*
@@ -410,14 +410,19 @@ static int find_resource(struct resource *root, struct resource *new,
tmp.end = root->end;

resource_clip(&tmp, min, max);
- tmp.start = ALIGN(tmp.start, align);

- alloc.start = alignf(alignf_data, &tmp, size, align);
- alloc.end = alloc.start + size - 1;
- if (resource_contains(&tmp, &alloc)) {
- new->start = alloc.start;
- new->end = alloc.end;
- return 0;
+ /* Check for overflow after ALIGN() */
+ avail = *new;
+ avail.start = ALIGN(tmp.start, align);
+ avail.end = tmp.end;
+ if (avail.start >= tmp.start) {
+ alloc.start = alignf(alignf_data, &avail, size, align);
+ alloc.end = alloc.start + size - 1;
+ if (resource_contains(&avail, &alloc)) {
+ new->start = alloc.start;
+ new->end = alloc.end;
+ return 0;
+ }
}
if (!this)
break;