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
47ea91b4052d ("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/s5hpo37d5l8.wl-tiwai@suse.de
Fixes: 23c570a67448 ("resource: ability to resize an allocated resource")
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reported-by: Michael Henders <hendersm@shaw.ca>
Tested-by: Michael Henders <hendersm@shaw.ca>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Ram Pai <linuxram@us.ibm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/resource.c b/kernel/resource.c
index e270b50..2af6c03 100644 (file)
--- a/kernel/resource.c
+++ b/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;