linux-kernel - [PATCH] arch_check_bp_in_kernelspace: fix the range check

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Date:	Fri, 9 Nov 2012 19:29:43 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Amnon Shiloh <u3557@...o.sublimeip.com>,
	linux-kernel@...r.kernel.org
Subject: [PATCH] arch_check_bp_in_kernelspace: fix the range check

arch_check_bp_in_kernelspace() tries to avoid the overflow and does 2
TASK_SIZE checks but it needs OR, not AND. Consider va = TASK_SIZE -1
and len = 2 case.

Note: TASK_SIZE doesn't look right at least on x86, I think it should
be replaced by TASK_SIZE_MAX.

Signed-off-by: Oleg Nesterov <oleg@...hat.com>

--- x/arch/arm64/kernel/hw_breakpoint.c
+++ x/arch/arm64/kernel/hw_breakpoint.c
@@ -293,7 +293,7 @@ int arch_check_bp_in_kernelspace(struct 
 	va = info->address;
 	len = get_hbp_len(info->ctrl.len);
 
-	return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
+	return (va >= TASK_SIZE) || ((va + len - 1) >= TASK_SIZE);
 }
 
 /*
--- x/arch/arm/kernel/hw_breakpoint.c
+++ x/arch/arm/kernel/hw_breakpoint.c
@@ -464,7 +464,7 @@ int arch_check_bp_in_kernelspace(struct 
 	va = info->address;
 	len = get_hbp_len(info->ctrl.len);
 
-	return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
+	return (va >= TASK_SIZE) || ((va + len - 1) >= TASK_SIZE);
 }
 
 /*
--- x/arch/sh/kernel/hw_breakpoint.c
+++ x/arch/sh/kernel/hw_breakpoint.c
@@ -132,7 +132,7 @@ int arch_check_bp_in_kernelspace(struct 
 	va = info->address;
 	len = get_hbp_len(info->len);
 
-	return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
+	return (va >= TASK_SIZE) || ((va + len - 1) >= TASK_SIZE);
 }
 
 int arch_bp_generic_fields(int sh_len, int sh_type,
--- x/arch/x86/kernel/hw_breakpoint.c
+++ x/arch/x86/kernel/hw_breakpoint.c
@@ -200,7 +200,7 @@ int arch_check_bp_in_kernelspace(struct 
 	va = info->address;
 	len = get_hbp_len(info->len);
 
-	return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
+	return (va >= TASK_SIZE) || ((va + len - 1) >= TASK_SIZE);
 }
 
 int arch_bp_generic_fields(int x86_len, int x86_type,

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