rcuc info output in print_cpu_stall_info() contains
possible buffer overflow in the case of huge jiffies
difference. The situation seems improbable, but, buffer
overflow, still.
Also, unsigned jiffies difference printed as (signed)
%ld. This is intentional for debugging purposes, but
it is not obvious from the code.
Change sprintf to snprintf and add clarifying comment
about intention of %ld format.
Found by Linux Verification Center (linuxtesting.org) with SVACE.
Fixes: 245a62982502 ("rcu: Dump rcuc kthread status for CPUs not reporting quiescent state")
Signed-off-by: Nikita Kiryushin <kiryushin@xxxxxxxx>
---
v2: Remove signed to unsigned print format change as
Paul E. McKenney <paulmck@xxxxxxxxxx> suggested, add format
intention clarification comment
kernel/rcu/tree_stall.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
index 5d666428546b..b972fe9f07a6 100644
--- a/kernel/rcu/tree_stall.h
+++ b/kernel/rcu/tree_stall.h
@@ -504,7 +504,8 @@ static void print_cpu_stall_info(int cpu)
rcu_dynticks_in_eqs(rcu_dynticks_snap(cpu));
rcuc_starved = rcu_is_rcuc_kthread_starving(rdp, &j);
if (rcuc_starved)
- sprintf(buf, " rcuc=%ld jiffies(starved)", j);
+ /* %ld is intentional, for easier bug detection */
+ snprintf(buf, sizeof(buf), " rcuc=%ld jiffies(starved)", j);
pr_err("\t%d-%c%c%c%c: (%lu %s) idle=%04x/%ld/%#lx softirq=%u/%u fqs=%ld%s%s\n",
cpu,
"O."[!!cpu_online(cpu)],
--
2.34.1
