linux-kernel - [PATCH v2] resource: Fix integer overflow at reallocation

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Message-Id: <20180408072026.27365-1-tiwai@suse.de>
Date:   Sun,  8 Apr 2018 09:20:26 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Ram Pai <linuxram@...ibm.com>, Bjorn Helgaas <bhelgaas@...gle.com>,
        Michael Henders <hendersm@...w.ca>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] 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 resource assigned
after PCI resource 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 in resource_contains() to see
whether the given resource has a valid range for avoiding the integer
overflow problem.

Bugzilla: http://bugzilla.opensuse.org/show_bug.cgi?id=1086739
Fixes: 23c570a67448 ("resource: ability to resize an allocated resource")
Reported-and-tested-by: Michael Henders <hendersm@...w.ca>
Reviewed-by: Ram Pai <linuxram@...ibm.com>
Cc: <stable@...r.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
---

Andrew, could you pick this? It's still in a wild west...
Thanks!

v1->v2: check in resource_contains() instead of in __find_resource()

 include/linux/ioport.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/include/linux/ioport.h b/include/linux/ioport.h
index da0ebaec25f0..466d7be046eb 100644
--- a/include/linux/ioport.h
+++ b/include/linux/ioport.h
@@ -212,6 +212,9 @@ static inline bool resource_contains(struct resource *r1, struct resource *r2)
 		return false;
 	if (r1->flags & IORESOURCE_UNSET || r2->flags & IORESOURCE_UNSET)
 		return false;
+	/* sanity check whether it's a valid resource range */
+	if (r2->end < r2->start)
+		return false;
 	return r1->start <= r2->start && r1->end >= r2->end;
 }

-- 
2.16.3