Hi Grant, 2014-05-27 4:19 GMT-07:00 Grant Likely <grant.likely@xxxxxxxxxx>: > On Fri, 23 May 2014 12:43:11 -0700, Florian Fainelli <f.fainelli@xxxxxxxxx> wrote: >> Add an early check for the node argument in >> of_get_next_available_child() to avoid dereferencing a NULL node pointer >> a few lines after. >> >> CC: Daniel Mack <zonque@xxxxxxxxx> >> Signed-off-by: Florian Fainelli <f.fainelli@xxxxxxxxx> > > Is there a bug that exposed this path? Daniel sent a patch recently [1] which makes us call for_each_available_child_of_node() on a potentially NULL node argument. The reason for that is that the loop is supposed to iterate over child nodes (Ethernet PHY nodes) of a given MDIO bus node. There might be non-DT probed MDIO buses registered in the system (e.g: the fixed MDIO bus), which do not have a valid of_node pointer. Since then, Daniel updated his patch to also check for the MDIO bus device_node pointer to be non-NULL, but I feel like we should also but defensive here. Presumably this situation could happen with e.g: i2c busses, spi busses in a system that mixes both DT-probed and non-DT probed devices. > I'd like some more justification > before merging this patch, particularly considering of_get_next_child() > doesn't check for it either, but you're not modifying that function. Good catch, it should also be updated. [1]: http://patchwork.ozlabs.org/patch/347712/ > > g. > >> --- >> drivers/of/base.c | 3 +++ >> 1 file changed, 3 insertions(+) >> >> diff --git a/drivers/of/base.c b/drivers/of/base.c >> index e67b308819c9..9a71bfac78ae 100644 >> --- a/drivers/of/base.c >> +++ b/drivers/of/base.c >> @@ -746,6 +746,9 @@ struct device_node *of_get_next_available_child(const struct device_node *node, >> struct device_node *next; >> unsigned long flags; >> >> + if (!node) >> + return NULL; >> + >> raw_spin_lock_irqsave(&devtree_lock, flags); >> next = prev ? prev->sibling : node->child; >> for (; next; next = next->sibling) { >> -- >> 1.9.1 >> > -- Florian -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
