| Message ID | 20230810162442.9863-4-yury.norov@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | sched fixes | expand |
Hi Yury, On 2023/8/11 0:24, Yury Norov wrote: > When the node provided by user is CPU-less, corresponding record in > sched_domains_numa_masks is not set. Trying to dereference it in the > following code leads to kernel crash. > > To avoid it, start searching from the nearest node with CPUs. > > Fixes: cd7f55359c90 ("sched: add sched_numa_find_nth_cpu()") > Reported-by: Yicong Yang <yangyicong@hisilicon.com> > Closes: https://lore.kernel.org/lkml/CAAH8bW8C5humYnfpW3y5ypwx0E-09A3QxFE1JFzR66v+mO4XfA@mail.gmail.com/T/ > Reported-by: Guenter Roeck <linux@roeck-us.net> > Closes: https://lore.kernel.org/lkml/ZMHSNQfv39HN068m@yury-ThinkPad/T/#mf6431cb0b7f6f05193c41adeee444bc95bf2b1c4 > Signed-off-by: Yury Norov <yury.norov@gmail.com> > --- > > This has been discovered and fixed by Yicong Yang: > > https://lore.kernel.org/lkml/CAAH8bW8C5humYnfpW3y5ypwx0E-09A3QxFE1JFzR66v+mO4XfA@mail.gmail.com/T/ > > When discovering Guenter's failure report for sparc64, I found it's due to > the same problem. And while fixing, I found an opportunity to generalize > nearest NUMA node search and avoid code duplication. > > Yicong, if you like this approach, please feel free to add your co-developed-by > or any appropriate tags. > Looks fine to me. One nit below. Reviewed-by: Yicong Yang <yangyicong@hisilicon.com> > kernel/sched/topology.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > index d3a3b2646ec4..66b387172b6f 100644 > --- a/kernel/sched/topology.c > +++ b/kernel/sched/topology.c > @@ -2113,10 +2113,14 @@ static int hop_cmp(const void *a, const void *b) > */ > int sched_numa_find_nth_cpu(const struct cpumask *cpus, int cpu, int node) > { > - struct __cmp_key k = { .cpus = cpus, .node = node, .cpu = cpu }; > + struct __cmp_key k = { .cpus = cpus, .cpu = cpu }; > struct cpumask ***hop_masks; > int hop, ret = nr_cpu_ids; > > + /* CPU-less node entries are uninitialized in sched_domains_numa_masks */ > + node = numa_nearest_node(node, N_CPU); > + k.node = node; > + We may also have problem if node == NUMA_NO_NODE, is it better to mention this in the function comment or check it before we going on? Currently this function is only used in cpumask_local_spread() and the caller has already checked it, but considering this is an export function so somebody may use it directly. I wondering whether we should put this block within the protection of rcu_read_lock() for some issues like hotplug or not. Is it possible if @node become CPU-less subsequently? > rcu_read_lock(); > > k.masks = rcu_dereference(sched_domains_numa_masks); >
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index d3a3b2646ec4..66b387172b6f 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -2113,10 +2113,14 @@ static int hop_cmp(const void *a, const void *b) */ int sched_numa_find_nth_cpu(const struct cpumask *cpus, int cpu, int node) { - struct __cmp_key k = { .cpus = cpus, .node = node, .cpu = cpu }; + struct __cmp_key k = { .cpus = cpus, .cpu = cpu }; struct cpumask ***hop_masks; int hop, ret = nr_cpu_ids; + /* CPU-less node entries are uninitialized in sched_domains_numa_masks */ + node = numa_nearest_node(node, N_CPU); + k.node = node; + rcu_read_lock(); k.masks = rcu_dereference(sched_domains_numa_masks);
When the node provided by user is CPU-less, corresponding record in sched_domains_numa_masks is not set. Trying to dereference it in the following code leads to kernel crash. To avoid it, start searching from the nearest node with CPUs. Fixes: cd7f55359c90 ("sched: add sched_numa_find_nth_cpu()") Reported-by: Yicong Yang <yangyicong@hisilicon.com> Closes: https://lore.kernel.org/lkml/CAAH8bW8C5humYnfpW3y5ypwx0E-09A3QxFE1JFzR66v+mO4XfA@mail.gmail.com/T/ Reported-by: Guenter Roeck <linux@roeck-us.net> Closes: https://lore.kernel.org/lkml/ZMHSNQfv39HN068m@yury-ThinkPad/T/#mf6431cb0b7f6f05193c41adeee444bc95bf2b1c4 Signed-off-by: Yury Norov <yury.norov@gmail.com> --- This has been discovered and fixed by Yicong Yang: https://lore.kernel.org/lkml/CAAH8bW8C5humYnfpW3y5ypwx0E-09A3QxFE1JFzR66v+mO4XfA@mail.gmail.com/T/ When discovering Guenter's failure report for sparc64, I found it's due to the same problem. And while fixing, I found an opportunity to generalize nearest NUMA node search and avoid code duplication. Yicong, if you like this approach, please feel free to add your co-developed-by or any appropriate tags. kernel/sched/topology.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)