Re: [PATCH v4 06/14] of: property: Avoiding using uninitialized variable @imaplen in parse_interrupt_map()

[Krzysztof Kozlowski]

On Sat, Jan 11, 2025 at 06:34:21AM +0800, Zijun Hu wrote:
> On 2025/1/11 04:26, Rob Herring wrote:
> > On Thu, Jan 09, 2025 at 09:26:57PM +0800, Zijun Hu wrote:
> >> From: Zijun Hu <quic_zijuhu@xxxxxxxxxxx>
> >>
> >> parse_interrupt_map() will use uninitialized variable @imaplen if fails
> >> to get property 'interrupt-map'.
> >>
> >> Fix by using the variable after successfully getting the property.
> >>
> >> Fixes: e7985f43609c ("of: property: Fix fw_devlink handling of interrupt-map")
> >> Signed-off-by: Zijun Hu <quic_zijuhu@xxxxxxxxxxx>
> >> ---
> >>  drivers/of/property.c | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/drivers/of/property.c b/drivers/of/property.c
> >> index dca1a3ebccae1093b2b11f51e8e692bca854d0e3..6245cbff3527d762c16e7f4b7b7b3d4f2e9ddbe6 100644
> >> --- a/drivers/of/property.c
> >> +++ b/drivers/of/property.c
> >> @@ -1391,9 +1391,9 @@ static struct device_node *parse_interrupt_map(struct device_node *np,
> >>  	addrcells = of_bus_n_addr_cells(np);
> >>  
> >>  	imap = of_get_property(np, "interrupt-map", &imaplen);
> >> -	imaplen /= sizeof(*imap);
> >>  	if (!imap)
> >>  		return NULL;
> >> +	imaplen /= sizeof(*imap);
> > 
> > sizeof() is a compile time constant, there's not an actual dereference 
> > here.
> > 
> 
> the uninitialized variable is @imaplen, and not sizeof(*imap).

Correct. I think error is harmless, because whatever stack/random value
of imaplen we use in 'imaplen / =sizeof', we immediately return.

Anyway, for code correctness and silencing whatever warnings there are
(if there are you should actually paste them in commit msg):

Reviewed-by: Krzysztof Kozlowski <krzk@xxxxxxxxxx>

Best regards,
Krzysztof