linux-kernel - [PATCH v2] x86/traps: do not hash pointers in handle_stack

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Message-Id: <20200207154915.83739-1-edumazet@google.com>
Date:   Fri,  7 Feb 2020 07:49:15 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH v2] x86/traps: do not hash pointers in handle_stack_overflow()

Mangling stack pointers in handle_stack_overflow() is moot,
as registers (including RSP/RBP) are clear anyway.

Also switch to pr_emerg() as suggested by Thomas.

BUG: stack guard page was hit at 0000000063381e80 (stack is 000000008edc5696..0000000012256c50)
kernel stack overflow (double-fault): 0000 [#1] PREEMPT SMP KASAN
...
RSP: 0018:ffffc90002c1ffc0 EFLAGS: 00010802
RAX: 1ffff11004a0094c RBX: ffff888025004180 RCX: c9d82d1007bb146c
RDX: dffffc0000000000 RSI: ffff888025004a40 RDI: ffff888025004180
RBP: ffffc90002c201c0 R08: dffffc0000000000 R09: fffffbfff1405915
R10: fffffbfff1405915 R11: 0000000000000000 R12: ffff888025004a60
R13: ffff888025004a10 R14: c9d82d1007bb146c R15: ffff888025004180
...

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/traps.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 6ef00eb6fbb925e86109f86845e2b3ccef4023ec..318df13e267638c4888f1c3f611aff34818b3bd2 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -296,7 +296,7 @@ __visible void __noreturn handle_stack_overflow(const char *message,
 						struct pt_regs *regs,
 						unsigned long fault_address)
 {
-	printk(KERN_EMERG "BUG: stack guard page was hit at %p (stack is %p..%p)\n",
+	pr_emerg("BUG: stack guard page was hit at %px (stack is %px..%px)\n",
 		 (void *)fault_address, current->stack,
 		 (char *)current->stack + THREAD_SIZE - 1);
 	die(message, regs, 0);
-- 
2.25.0.341.g760bfbb309-goog