From: Ram Pai <firstname.lastname@example.org> To: Andrew Morton <email@example.com> Cc: Takashi Iwai <firstname.lastname@example.org>, Bjorn Helgaas <email@example.com>, Michael Henders <firstname.lastname@example.org>, email@example.com Subject: Re: [PATCH v2] resource: Fix integer overflow at reallocation Date: Tue, 10 Apr 2018 17:37:44 -0700 [thread overview] Message-ID: <20180411003744.GC15890@ram.oc3035372033.ibm.com> (raw) In-Reply-To: <firstname.lastname@example.org> On Tue, Apr 10, 2018 at 01:42:39PM -0700, Andrew Morton wrote: > On Tue, 10 Apr 2018 06:54:11 +0200 Takashi Iwai <email@example.com> wrote: > > > On Tue, 10 Apr 2018 02:23:26 +0200, > > Andrew Morton wrote: > > > > > > On Sun, 8 Apr 2018 09:20:26 +0200 Takashi Iwai <firstname.lastname@example.org> wrote: > > > > > > > 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. > > > > > > > > ... > > > > > > > > --- 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; > > > > } > > > > > > This doesn't look like the correct place to handle this? Clearly .end > > > < .start is an invalid state for a resource and we should never have > > > constructed such a thing in the first place? So adding a check at the > > > place where this resource was initially created seems to be the correct > > > fix? > > > > Yes, that was also my first thought and actually the v1 patch was like > > that. > > Yes, I do prefer. > > > The v2 one was by Ram's suggestion so that we can cover > > potential bugs by all other callers as well. > > That could be done as a separate thing? the first approach will fix overflows in just that particular case. The second approach will catch and error-out overflows anywhere. There is a short-term down side to the second approach; it might cause a slew of error reports but will eventually help clean up all bad behavior. RP
next prev parent reply other threads:[~2018-04-11 0:37 UTC|newest] Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top 2018-04-08 7:20 Takashi Iwai 2018-04-10 0:23 ` Andrew Morton 2018-04-10 4:54 ` Takashi Iwai 2018-04-10 20:42 ` Andrew Morton 2018-04-11 0:37 ` Ram Pai [this message] 2018-04-11 6:16 ` Takashi Iwai 2018-04-11 14:08 ` Ram Pai
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