Messages in this thread Patch in this message | | | From | Valentin Schneider <> | Subject | [PATCH v2 2/9] sched/debug: Make sd->flags sysctl read-only | Date | Wed, 11 Mar 2020 18:15:54 +0000 |
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Writing to the sysctl of a sched_domain->flags directly updates the value of the field, and goes nowhere near update_top_cache_domain(). This means that the cached domain pointers can end up containing stale data (e.g. the domain pointed to doesn't have the relevant flag set anymore).
Explicit domain walks that check for flags will be affected by the write, but this won't be in sync with the cached pointers which will still point to the domains that were cached at the last sched_domain build.
In other words, writing to this interface is playing a dangerous game. It could be made to trigger an update of the cached sched_domain pointers when written to, but this does not seem to be worth the trouble. Make it read-only.
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> --- kernel/sched/debug.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 8331bc04aea2..d86f7c21feff 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -258,7 +258,7 @@ sd_alloc_ctl_domain_table(struct sched_domain *sd) set_table_entry(&table[2], "busy_factor", &sd->busy_factor, sizeof(int), 0644, proc_dointvec_minmax); set_table_entry(&table[3], "imbalance_pct", &sd->imbalance_pct, sizeof(int), 0644, proc_dointvec_minmax); set_table_entry(&table[4], "cache_nice_tries", &sd->cache_nice_tries, sizeof(int), 0644, proc_dointvec_minmax); - set_table_entry(&table[5], "flags", &sd->flags, sizeof(int), 0644, proc_dointvec_minmax); + set_table_entry(&table[5], "flags", &sd->flags, sizeof(int), 0444, proc_dointvec_minmax); set_table_entry(&table[6], "max_newidle_lb_cost", &sd->max_newidle_lb_cost, sizeof(long), 0644, proc_doulongvec_minmax); set_table_entry(&table[7], "name", sd->name, CORENAME_MAX_SIZE, 0444, proc_dostring); /* &table[8] is terminator */ -- 2.24.0
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