On Tue, Jan 18, 2022 at 10:56:12AM -0800, Bjorn Andersson wrote: > Occasionally during boot the Qualcomm cpufreq driver was able to cause > an invalid memory access in topology_update_thermal_pressure() on the > line: > > if (max_freq <= capped_freq) > > It turns out that this was caused by a race, which resulted in the > cpumask passed to the function being empty, in which case > cpumask_first() will return a cpu beyond the number of valid cpus, which > when used to access the per_cpu max_freq would return invalid pointer. > > The bug in the Qualcomm cpufreq driver is being fixed, but having a > sanity check of the arguments would have saved quite a bit of time and > it's not unlikely that others will run into the same issue. > > Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx> > --- > drivers/base/arch_topology.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c > index 976154140f0b..6560a0c3b969 100644 > --- a/drivers/base/arch_topology.c > +++ b/drivers/base/arch_topology.c > @@ -177,6 +177,9 @@ void topology_update_thermal_pressure(const struct cpumask *cpus, > u32 max_freq; > int cpu; > > + if (WARN_ON(cpumask_empty(cpus))) > + return; > + Why can't the caller check and call this only when cpus is not empty ? IIUC there are many such APIs that use cpumask and could result in similar issues if called with empty cpus. Probably we could add a note that cpus must not be empty if that helps the callers ? -- Regards, Sudeep
