linux-kernel - Re: [PATCH] PCI: mvebu: Fix uninitialized variable in mvebu_get_tgt

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Date:	Fri, 05 Sep 2014 19:51:27 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	linux-pci@...r.kernel.org, Jason Cooper <jason@...edaemon.net>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: mvebu: Fix uninitialized variable in mvebu_get_tgt_attr()

On Friday 05 September 2014 11:41:22 Bjorn Helgaas wrote:
> On Fri, Aug 08, 2014 at 05:34:05PM +0200, Geert Uytterhoeven wrote:
> > drivers/pci/host/pci-mvebu.c: In function 'mvebu_get_tgt_attr':
> > drivers/pci/host/pci-mvebu.c:887:39: warning: 'rtype' may be used uninitialized in this function [-Wmaybe-uninitialized]
> >    if (slot == PCI_SLOT(devfn) && type == rtype) {
> >                                        ^
> > 
> > If there's ever gonna be a configuration space or 64-bit memory space
> > entry in DT, rtype will be uninitialized, and the wrong entry may be
> > returned.
> > 
> > Initialize rtype to 0 (which is an unused IORESOURCE_* type) to fix this.
> > 
> > Introduced in commit 11be65472a427dcf7a11ab6e3e3628f1c6768b5b ("PCI:
> > mvebu: Adapt to the new device tree layout").
> > 
> > Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
> > ---
> > Alternatively, should the "else if (DT_FLAGS_TO_TYPE(flags) ==
> > DT_TYPE_MEM32)" just be changed to "else", assuming there can never be
> > other entries than for I/O or 32-bit memory space?
> > ---
> >  drivers/pci/host/pci-mvebu.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/host/pci-mvebu.c b/drivers/pci/host/pci-mvebu.c
> > index ce23e0f076b6..9515f0d13fd4 100644
> > --- a/drivers/pci/host/pci-mvebu.c
> > +++ b/drivers/pci/host/pci-mvebu.c
> > @@ -877,7 +877,7 @@ static int mvebu_get_tgt_attr(struct device_node *np, int devfn,
> >  		u32 flags = of_read_number(range, 1);
> >  		u32 slot = of_read_number(range + 1, 1);
> >  		u64 cpuaddr = of_read_number(range + na, pna);
> > -		unsigned long rtype;
> > +		unsigned long rtype = 0;
> >  
> >  		if (DT_FLAGS_TO_TYPE(flags) == DT_TYPE_IO)
> >  			rtype = IORESOURCE_IO;
> 
> This fix looks right to me.  I added a stable tag as follows.  Thomas
> and/or Jason, and you ack this?


I had a local fix for this, which I haven't gotten around to
send a proper changelog for, but it seems like a more appropriate
fix, avoiding the spurious initialization.

The other fix looks technically correct as well though.

	Arnd

diff --git a/drivers/pci/host/pci-mvebu.c b/drivers/pci/host/pci-mvebu.c
index a8c6f1a92e0f..678849836649 100644
--- a/drivers/pci/host/pci-mvebu.c
+++ b/drivers/pci/host/pci-mvebu.c
@@ -883,6 +883,8 @@ static int mvebu_get_tgt_attr(struct device_node *np, int devfn,
 			rtype = IORESOURCE_IO;
 		else if (DT_FLAGS_TO_TYPE(flags) == DT_TYPE_MEM32)
 			rtype = IORESOURCE_MEM;
+		else
+			rtype = -1;
 
 		if (slot == PCI_SLOT(devfn) && type == rtype) {
 			*tgt = DT_CPUADDR_TO_TARGET(cpuaddr);

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