resources: handle overflow when aligning start of available area

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>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

1 files changed, 13 insertions, 8 deletions

diff --git a/kernel/resource.c b/kernel/resource.c
index 89d50412508c..e15b922d4ba4 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;