linux-kernel - [PATCH] arm: fixed backtrace when task running on another cpu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Date:   Sat, 18 Apr 2020 19:14:18 +0800
From:   Wang Qing <wangqing@...o.com>
To:     Russell King <linux@...linux.org.uk>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Enrico Weigelt <info@...ux.net>,
        Allison Randal <allison@...utok.net>,
        Wang Qing <wangqing@...o.com>,
        Vincent Whitchurch <vincent.whitchurch@...s.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     opensource.kernel@...o.com
Subject: [PATCH] arm: fixed backtrace when task running on another cpu

We cannot get FP when the task is currently running on another CPU,
in this case, current stack is printed instead of the task.
Also, thread_saved_fp() is the last time the task was switched out,
we should not use too.

Signed-off-by: Wang Qing <wangqing@...o.com>
---
 arch/arm/kernel/traps.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm/kernel/traps.c b/arch/arm/kernel/traps.c
index 1e70e72..24e860a 100644
--- a/arch/arm/kernel/traps.c
+++ b/arch/arm/kernel/traps.c
@@ -222,6 +222,9 @@ static void dump_backtrace(struct pt_regs *regs, struct task_struct *tsk)
 	} else if (tsk != current) {
 		fp = thread_saved_fp(tsk);
 		mode = 0x10;
+	} else if (task_curr(tsk))
+		pr_info("tsk is running on another CPU, not trace!\n");
+		fp = 0;
 	} else {
 		asm("mov %0, fp" : "=r" (fp) : : "cc");
 		mode = 0x10;
-- 
2.7.4