blob: 2531308698036e2a34658054e5836a1c5a9e8b5f [file] [log] [blame]
From df6da205d22091c8a4bd228000ec963c4060c56f Mon Sep 17 00:00:00 2001
From: Valentin Schneider <>
Date: Wed, 15 Apr 2020 22:05:05 +0100
Subject: [PATCH] sched/debug: Make sd->flags sysctl read-only
commit 9818427c6270a9ce8c52c8621026fe9cebae0f92 upstream.
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
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
Signed-off-by: Valentin Schneider <>
Signed-off-by: Peter Zijlstra (Intel) <>
Signed-off-by: Paul Gortmaker <>
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 14c6a8716ba1..0650be5f5bc7 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -272,7 +272,7 @@ sd_alloc_ctl_domain_table(struct sched_domain *sd)
set_table_entry(&table[7] , "busy_factor", &sd->busy_factor, sizeof(int) , 0644, proc_dointvec_minmax, false);
set_table_entry(&table[8] , "imbalance_pct", &sd->imbalance_pct, sizeof(int) , 0644, proc_dointvec_minmax, false);
set_table_entry(&table[9] , "cache_nice_tries", &sd->cache_nice_tries, sizeof(int) , 0644, proc_dointvec_minmax, false);
- set_table_entry(&table[10], "flags", &sd->flags, sizeof(int) , 0644, proc_dointvec_minmax, false);
+ set_table_entry(&table[10], "flags", &sd->flags, sizeof(int) , 0444, proc_dointvec_minmax, false);
set_table_entry(&table[11], "max_newidle_lb_cost", &sd->max_newidle_lb_cost, sizeof(long), 0644, proc_doulongvec_minmax, false);
set_table_entry(&table[12], "name", sd->name, CORENAME_MAX_SIZE, 0444, proc_dostring, false);
/* &table[13] is terminator */