linux-kernel - [PATCH 3.2 023/153] x86/entry/64: Don't use IST entry for #BP 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:   Wed, 30 May 2018 11:52:41 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Andy Lutomirski" <luto@...nel.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>
Subject: [PATCH 3.2 023/153] x86/entry/64: Don't use IST entry for #BP stack

3.2.102-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Andy Lutomirski <luto@...nel.org>

commit d8ba61ba58c88d5207c1ba2f7d9a2280e7d03be9 upstream.

There's nothing IST-worthy about #BP/int3.  We don't allow kprobes
in the small handful of places in the kernel that run at CPL0 with
an invalid stack, and 32-bit kernels have used normal interrupt
gates for #BP forever.

Furthermore, we don't allow kprobes in places that have usergs while
in kernel mode, so "paranoid" is also unnecessary.

Signed-off-by: Andy Lutomirski <luto@...nel.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
[carnil: Backport to 3.16:
 - Adjust finename change: arch/x86/kernel/entry_64.S
 - Context changes
]
[bwh: Rebase on top of "x86/traps: Enable DEBUG_STACK after cpu_init() for
 TRAP_DB/BP", and restore change in trap_init() instead of early_trap_init().
 Backport to 3.2:
 - Use zeroentry macro in entry_64.S
 - Drop changes related to breakpoint-in-NMI support
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -1401,7 +1401,7 @@ apicinterrupt XEN_HVM_EVTCHN_CALLBACK \
 	.pushsection .kprobes.text, "ax"
 
 paranoidzeroentry_ist debug do_debug DEBUG_STACK
-paranoidzeroentry_ist int3 do_int3 DEBUG_STACK
+zeroentry int3 do_int3
 errorentry stack_segment do_stack_segment
 #ifdef CONFIG_XEN
 zeroentry xen_debug do_debug
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -314,7 +314,6 @@ gp_in_kernel:
 	die("general protection fault", regs, error_code);
 }
 
-/* May run on IST stack. */
 dotraplinkage void __kprobes do_int3(struct pt_regs *regs, long error_code)
 {
 #ifdef CONFIG_KGDB_LOW_LEVEL_TRAP
@@ -790,13 +789,11 @@ void __init trap_init(void)
 	cpu_init();
 
 	/*
-	 * X86_TRAP_DB and X86_TRAP_BP have been set
-	 * in early_trap_init(). However, DEBUG_STACK works only after
-	 * cpu_init() loads TSS. See comments in early_trap_init().
+	 * X86_TRAP_DB was installed in early_trap_init(). However,
+	 * DEBUG_STACK works only after cpu_init() loads TSS. See comments
+	 * in early_trap_init().
 	 */
 	set_intr_gate_ist(X86_TRAP_DB, &debug, DEBUG_STACK);
-	/* int3 can be called from all */
-	set_system_intr_gate_ist(X86_TRAP_BP, &int3, DEBUG_STACK);
 
 	x86_init.irqs.trap_init();
 }