linux-kernel - [PATCH] Fix non-lazy GS handling in sys

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-next>] [day] [month] [year] [list]

Date:	Sat, 06 Jun 2009 20:23:25 +0200
From:	Lubomir Rintel <lkundrak@...sk>
To:	Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	x86@...nel.org
Subject: [PATCH] Fix non-lazy GS handling in sys_vm86()

This fixes a stack corruption panic or null dereference oops due to
a bad GS in resume_userspace() when returning from sys_vm86() and calling
lockdep_sys_exit().

Only a problem when CONFIG_LOCKDEP and CONFIG_CC_STACKPROTECTOR enabled.

Signed-off-by: Lubomir Rintel <lkundrak@...sk>
---
 arch/x86/kernel/vm86_32.c |   13 +++++++------
 1 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/vm86_32.c b/arch/x86/kernel/vm86_32.c
index d7ac84e..177d976 100644
--- a/arch/x86/kernel/vm86_32.c
+++ b/arch/x86/kernel/vm86_32.c
@@ -287,10 +287,9 @@ static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk
 	info->regs.pt.ds = 0;
 	info->regs.pt.es = 0;
 	info->regs.pt.fs = 0;
-
-/* we are clearing gs later just before "jmp resume_userspace",
- * because it is not saved/restored.
- */
+#ifndef CONFIG_X86_32_LAZY_GS
+	info->regs.pt.gs = 0;
+#endif
 
 /*
  * The flags register is also special: we cannot trust that the user
@@ -343,10 +342,12 @@ static void do_sys_vm86(struct kernel_vm86_struct *info, struct task_struct *tsk
 	__asm__ __volatile__(
 		"movl %0,%%esp\n\t"
 		"movl %1,%%ebp\n\t"
-		"mov  %2, %%gs\n\t"
+#ifdef CONFIG_X86_32_LAZY_GS
+		"mov  $0, %%gs\n\t"
+#endif
 		"jmp resume_userspace"
 		: /* no outputs */
-		:"r" (&info->regs), "r" (task_thread_info(tsk)), "r" (0));
+		:"r" (&info->regs), "r" (task_thread_info(tsk)));
 	/* we never return here */
 }
 

-- 
"Excuse all the blood" -- Dead

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/