Commit 95feabe8 authored by Nikita Kiryushin's avatar Nikita Kiryushin Committed by Yu Liao
Browse files

rcu: Fix buffer overflow in print_cpu_stall_info() 

stable inclusion
from stable-v6.6.33
commit afb39909bfb5c08111f99e21bf5be7505f59ff1c
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/IA6S9X
CVE: CVE-2024-38576

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=afb39909bfb5c08111f99e21bf5be7505f59ff1c



--------------------------------

[ Upstream commit 3758f7d9917bd7ef0482c4184c0ad673b4c4e069 ]

The rcuc-starvation output from print_cpu_stall_info() might overflow the
buffer if there is a huge difference in jiffies difference.  The situation
might seem improbable, but computers sometimes get very confused about
time, which can result in full-sized integers, and, in this case,
buffer overflow.

Also, the unsigned jiffies difference is printed using %ld, which is
normally for signed integers.  This is intentional for debugging purposes,
but it is not obvious from the code.

This commit therefore changes sprintf() to snprintf() and adds a
clarifying comment about intention of %ld format.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 245a6298 ("rcu: Dump rcuc kthread status for CPUs not reporting quiescent state")
Signed-off-by: default avatarNikita Kiryushin <kiryushin@ancud.ru>
Reviewed-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarUladzislau Rezki (Sony) <urezki@gmail.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
Signed-off-by: default avatarYu Liao <liaoyu15@huawei.com>
parent 307f7fa9

kernel/rcu/tree_stall.h

+2 −1
Original line number Diff line number Diff line
@@ -503,7 +503,8 @@ 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);

		// Print signed value, as negative values indicate a probable bug.

		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)],