linux-kernel - [PATCH 4/7] x86/dumpstack: If addr_limit is non-default, display it

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Date:	Tue, 24 May 2016 15:48:41 -0700
From:	Andy Lutomirski <luto@...nel.org>
To:	x86@...nel.org
Cc:	linux-kernel@...r.kernel.org, Borislav Petkov <bp@...en8.de>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>,
	Andy Lutomirski <luto@...nel.org>
Subject: [PATCH 4/7] x86/dumpstack: If addr_limit is non-default, display it

This will help debug OOPSes related to USER_DS vs KERNEL_DS.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
---
 arch/x86/kernel/dumpstack_32.c | 4 ++++
 arch/x86/kernel/dumpstack_64.c | 5 +++++
 2 files changed, 9 insertions(+)

diff --git a/arch/x86/kernel/dumpstack_32.c b/arch/x86/kernel/dumpstack_32.c
index 464ffd69b92e..5dbb08fd8291 100644
--- a/arch/x86/kernel/dumpstack_32.c
+++ b/arch/x86/kernel/dumpstack_32.c
@@ -124,8 +124,12 @@ show_stack_log_lvl(struct task_struct *task, struct pt_regs *regs,
 void show_regs(struct pt_regs *regs)
 {
 	int i;
+	struct thread_info *ti = current_thread_info();
 
 	show_regs_print_info(KERN_EMERG);
+	if (ti->addr_limit.seg != TASK_SIZE_MAX)
+		printk(KERN_DEFAULT "task.addr_limit: 0x%lx\n",
+		       ti->addr_limit.seg);
 	__show_regs(regs, !user_mode(regs));
 
 	/*
diff --git a/arch/x86/kernel/dumpstack_64.c b/arch/x86/kernel/dumpstack_64.c
index 5f1c6266eb30..2fdeb64dfed0 100644
--- a/arch/x86/kernel/dumpstack_64.c
+++ b/arch/x86/kernel/dumpstack_64.c
@@ -301,9 +301,14 @@ void show_regs(struct pt_regs *regs)
 {
 	int i;
 	unsigned long sp;
+	struct thread_info *ti = current_thread_info();
 
 	sp = regs->sp;
+
 	show_regs_print_info(KERN_DEFAULT);
+	if (ti->addr_limit.seg != TASK_SIZE_MAX)
+		printk(KERN_DEFAULT "task.addr_limit: 0x%lx\n",
+		       ti->addr_limit.seg);
 	__show_regs(regs, 1);
 
 	/*
-- 
2.5.5