From: Nikita Kiryushin kiryushin@ancud.ru

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=...

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[ 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: 245a62982502 ("rcu: Dump rcuc kthread status for CPUs not reporting quiescent state") Signed-off-by: Nikita Kiryushin kiryushin@ancud.ru Reviewed-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Paul E. McKenney paulmck@kernel.org Signed-off-by: Uladzislau Rezki (Sony) urezki@gmail.com Signed-off-by: Sasha Levin sashal@kernel.org Signed-off-by: Yu Liao liaoyu15@huawei.com --- 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 e09f4f624261..11a1fac3a589 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -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)],