From: Nelson Elhage <nelson.elhage@oracle.com>
Date: Tue, 20 Sep 2011 20:40:00 +0000 (-0400)
Subject: ksplice: Clear garbage data on the kernel stack when handling signals.
X-Git-Tag: v2.6.39-400.9.0~892
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=3b4659b5d14ca729408d68ac0bddf0f69cbfc92d;p=users%2Fjedix%2Flinux-maple.git

ksplice: Clear garbage data on the kernel stack when handling signals.
---

diff --git a/arch/x86/kernel/entry_32.S b/arch/x86/kernel/entry_32.S
index 5c1a91974918d..35c8120b25ecb 100644
--- a/arch/x86/kernel/entry_32.S
+++ b/arch/x86/kernel/entry_32.S
@@ -625,7 +625,7 @@ work_notifysig:				# deal with pending signals and
 	jne work_notifysig_v86		# returning to kernel-space or
 					# vm86-space
 	xorl %edx, %edx
-	call do_notify_resume
+	call clear_stack_do_notify_resume
 	jmp resume_userspace_sig
 
 	ALIGN
@@ -638,10 +638,37 @@ work_notifysig_v86:
 	movl %esp, %eax
 #endif
 	xorl %edx, %edx
-	call do_notify_resume
+	call clear_stack_do_notify_resume
 	jmp resume_userspace_sig
 END(work_pending)
 
+	# Clear the stack before handling signals
+	ALIGN
+#define STACK_CLEAR_WORDS	0x80
+ENTRY(clear_stack_do_notify_resume)
+	testl $_TIF_SIGPENDING, %ecx
+	jnz do_notify_resume
+
+	push %eax
+	push %ecx
+	push %edi
+
+	movl %esp, %edi
+	subl $4, %edi
+	movl $STACK_CLEAR_WORDS, %ecx
+	xorl %eax, %eax
+
+	std
+	rep stosl
+	cld
+
+	pop %edi
+	pop %ecx
+	pop %eax
+
+	jmp do_notify_resume
+END(clear_stack_do_notify_resume)
+
 	# perform syscall exit tracing
 	ALIGN
 syscall_trace_entry:
diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index 8a445a0c989e0..e1b62393ec434 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -660,7 +660,7 @@ int_signal:
 	jz 1f
 	movq %rsp,%rdi		# &ptregs -> arg1
 	xorl %esi,%esi		# oldset -> arg2
-	call do_notify_resume
+	call clear_stack_do_notify_resume
 1:	movl $_TIF_WORK_MASK,%edi
 int_restore_rest:
 	RESTORE_REST
@@ -919,7 +919,7 @@ retint_signal:
 	movq $-1,ORIG_RAX(%rsp)
 	xorl %esi,%esi		# oldset
 	movq %rsp,%rdi		# &pt_regs
-	call do_notify_resume
+	call clear_stack_do_notify_resume
 	RESTORE_REST
 	DISABLE_INTERRUPTS(CLBR_NONE)
 	TRACE_IRQS_OFF
@@ -1387,7 +1387,7 @@ paranoid_userspace:
 	ENABLE_INTERRUPTS(CLBR_NONE)
 	xorl %esi,%esi 			/* arg2: oldset */
 	movq %rsp,%rdi 			/* arg1: &pt_regs */
-	call do_notify_resume
+	call clear_stack_do_notify_resume
 	DISABLE_INTERRUPTS(CLBR_NONE)
 	TRACE_IRQS_OFF
 	jmp paranoid_userspace
@@ -1521,7 +1521,7 @@ nmi_userspace:
 	ENABLE_INTERRUPTS(CLBR_NONE)
 	xorl %esi,%esi 			/* arg2: oldset */
 	movq %rsp,%rdi 			/* arg1: &pt_regs */
-	call do_notify_resume
+	call clear_stack_do_notify_resume
 	DISABLE_INTERRUPTS(CLBR_NONE)
 	jmp nmi_userspace
 nmi_schedule:
@@ -1543,6 +1543,28 @@ ENTRY(ignore_sysret)
 	CFI_ENDPROC
 END(ignore_sysret)
 
+	# Clear the stack before handling signals
+#define STACK_CLEAR_WORDS	0x80
+ENTRY(clear_stack_do_notify_resume)
+	testl $_TIF_SIGPENDING, %edx
+	jnz do_notify_resume
+
+	pushq %rdi
+
+	movq %rsp, %rdi
+	subq $8, %rdi
+	movl $STACK_CLEAR_WORDS, %ecx
+	xorq %rax, %rax
+
+	std
+	rep stosq
+	cld
+
+	popq %rdi
+
+	jmp do_notify_resume
+END(clear_stack_do_notify_resume)
+
 /*
  * End of kprobes section
  */