linux-kernel - [RFC][PATCH 18/24] x86/pti: Execute system vector handlers on the kernel stack

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

Date:   Mon,  9 Nov 2020 12:23:13 +0100
From:   Alexandre Chartre <alexandre.chartre@...cle.com>
To:     "tglx@...utronix.de"@aserv0121.oracle.com,
        "mingo@...hat.com"@aserv0121.oracle.com,
        "bp@...en8.de"@aserv0121.oracle.com,
        "hpa@...or.com"@aserv0121.oracle.com,
        "x86@...nel.org"@aserv0121.oracle.com,
        "dave.hansen@...ux.intel.com"@aserv0121.oracle.com,
        "luto@...nel.org"@aserv0121.oracle.com,
        "peterz@...radead.org"@aserv0121.oracle.com,
        "linux-kernel@...r.kernel.org"@aserv0121.oracle.com,
        "thomas.lendacky@....com"@aserv0121.oracle.com,
        "jroedel@...e.de"@aserv0121.oracle.com
Cc:     "konrad.wilk@...cle.com"@aserv0121.oracle.com,
        "jan.setjeeilers@...cle.com"@aserv0121.oracle.com,
        "junaids@...gle.com"@aserv0121.oracle.com,
        "oweisse@...gle.com"@aserv0121.oracle.com,
        "rppt@...ux.vnet.ibm.com"@aserv0121.oracle.com,
        "graf@...zon.de"@aserv0121.oracle.com,
        "mgross@...ux.intel.com"@aserv0121.oracle.com,
        "kuzuno@...il.com"@aserv0121.oracle.com,
        "alexandre.chartre@...cle.com"@aserv0121.oracle.com
Subject: [RFC][PATCH 18/24] x86/pti: Execute system vector handlers on the kernel stack

After an interrupt/exception in userland, the kernel is entered
and it switches the stack to the PTI stack which is mapped both in
the kernel and in the user page-table. When executing the interrupt
function, switch to the kernel stack (which is mapped only in the
kernel page-table) so that no kernel data leak to the userland
through the stack.

Changes system vector handlers to execute on the kernel stack.

Signed-off-by: Alexandre Chartre <alexandre.chartre@...cle.com>
---
 arch/x86/include/asm/idtentry.h | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h
index a82e31b45442..0c5d9f027112 100644
--- a/arch/x86/include/asm/idtentry.h
+++ b/arch/x86/include/asm/idtentry.h
@@ -66,6 +66,17 @@ void run_idt_errcode(void (*func)(struct pt_regs *, unsigned long),
 	CALL_ON_STACK_2(pti_kernel_stack(regs), func, regs, error_code);
 }
 
+static __always_inline
+void run_sysvec(void (*func)(struct pt_regs *regs), struct pt_regs *regs)
+{
+	void *stack = pti_kernel_stack(regs);
+
+	if (stack)
+		asm_call_on_stack_1(stack, (void (*)(void))func, regs);
+	else
+		run_sysvec_on_irqstack_cond(func, regs);
+}
+
 /**
  * DECLARE_IDTENTRY - Declare functions for simple IDT entry points
  *		      No error code pushed by hardware
@@ -295,7 +306,7 @@ __visible noinstr void func(struct pt_regs *regs)			\
 	instrumentation_begin();					\
 	irq_enter_rcu();						\
 	kvm_set_cpu_l1tf_flush_l1d();					\
-	run_sysvec_on_irqstack_cond(__##func, regs);			\
+	run_sysvec(__##func, regs);					\
 	irq_exit_rcu();							\
 	instrumentation_end();						\
 	irqentry_exit(regs, state);					\
-- 
2.18.4