resource: fix integer overflow at reallocation

We've got a bug report indicating a kernel panic at booting on an x86-32
system, and it turned out to be the invalid PCI resource assigned after
reallocation.  __find_resource() first aligns the resource start address
and resets the end address with start+size-1 accordingly, then checks
whether it's contained.  Here the end address may overflow the integer,
although resource_contains() still returns true because the function
validates only start and end address.  So this ends up with returning an
invalid resource (start > end).

There was already an attempt to cover such a problem in the commit
47ea91b ("Resource: fix wrong resource window calculation"), but
this case is an overseen one.

This patch adds the validity check of the newly calculated resource for
avoiding the integer overflow problem.

Bugzilla: http://bugzilla.opensuse.org/show_bug.cgi?id=1086739
Link: http://lkml.kernel.org/r/[email protected]
Fixes: 23c570a ("resource: ability to resize an allocated resource")
Signed-off-by: Takashi Iwai <[email protected]>
Reported-by: Michael Henders <[email protected]>
Tested-by: Michael Henders <[email protected]>
Reviewed-by: Andrew Morton <[email protected]>
Cc: Ram Pai <[email protected]>
Cc: Bjorn Helgaas <[email protected]>
Cc: <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

kernel/resource.c

@@ -651,7 +651,8 @@ static int __find_resource(struct resource *root, struct resource *old,
 			alloc.start = constraint->alignf(constraint->alignf_data, &avail,
 					size, constraint->align);
 			alloc.end = alloc.start + size - 1;
-			if (resource_contains(&avail, &alloc)) {
+			if (alloc.start <= alloc.end &&
+			    resource_contains(&avail, &alloc)) {
 				new->start = alloc.start;
 				new->end = alloc.end;
 				return 0;