linux-kernel - [PATCH for 2.6.18-rc2] [3/8] i386/x86-64: Add user_mode checks to profile

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Date:	Sun, 16 Jul 2006 14:22:40 +0200
From:	"Andi Kleen" <ak@...e.de>
To:	torvalds@...l.org
Cc:	akpm@...l.org, discuss@...-64.org, linux-kernel@...r.kernel.org,
	levon@...ementarian.org
Subject: [PATCH for 2.6.18-rc2] [3/8] i386/x86-64: Add user_mode checks to profile_pc for oprofile


Fixes a obscure user space triggerable crash during oprifiling.

Oprofile calls profile_pc from NMIs even when user_mode(regs) is not true and
the program counter is inside the kernel lock section. This opens
a race - when a user program jumps to a kernel lock address and 
a NMI happens before the illegal page fault exception is raised
and the program has a unmapped esp or ebp then the kernel could
oops. NMIs have a higher priority than exceptions so that could
happen.

Add user_mode checks to i386/x86-64 profile_pc to prevent that.

Cc: John Levon <levon@...ementarian.org>
Signed-off-by: Andi Kleen <ak@...e.de>

---
 arch/i386/kernel/time.c   |    2 +-
 arch/x86_64/kernel/time.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

Index: linux/arch/i386/kernel/time.c
===================================================================
--- linux.orig/arch/i386/kernel/time.c
+++ linux/arch/i386/kernel/time.c
@@ -135,7 +135,7 @@ unsigned long profile_pc(struct pt_regs 
 {
 	unsigned long pc = instruction_pointer(regs);
 
-	if (in_lock_functions(pc))
+	if (!user_mode_vm(regs) && in_lock_functions(pc))
 		return *(unsigned long *)(regs->ebp + 4);
 
 	return pc;
Index: linux/arch/x86_64/kernel/time.c
===================================================================
--- linux.orig/arch/x86_64/kernel/time.c
+++ linux/arch/x86_64/kernel/time.c
@@ -195,7 +195,7 @@ unsigned long profile_pc(struct pt_regs 
 	   is just accounted to the spinlock function.
 	   Better would be to write these functions in assembler again
 	   and check exactly. */
-	if (in_lock_functions(pc)) {
+	if (!user_mode(regs) && in_lock_functions(pc)) {
 		char *v = *(char **)regs->rsp;
 		if ((v >= _stext && v <= _etext) ||
 			(v >= _sinittext && v <= _einittext) ||
-
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