linux-kernel - [11/11] KVM: S390: fix potential array overrun in intercept handling

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Date:	Tue, 26 Jan 2010 11:14:47 -0800
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Marcelo Tosatti <mtosatti@...hat.com>
Subject: [11/11] KVM: S390: fix potential array overrun in intercept handling

2.6.27-stable review patch.  If anyone has any objections, please let us know.

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

From: Christian Borntraeger <borntraeger@...ibm.com>

commit 062d5e9b0d714f449b261bb522eadaaf6f00f438 upstream.

kvm_handle_sie_intercept uses a jump table to get the intercept handler
for a SIE intercept. Static code analysis revealed a potential problem:
the intercept_funcs jump table was defined to contain (0x48 >> 2) entries,
but we only checked for code > 0x48 which would cause an off-by-one
array overflow if code == 0x48.

Use the compiler and ARRAY_SIZE to automatically set the limits.

Signed-off-by: Christian Borntraeger <borntraeger@...ibm.com>
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 arch/s390/kvm/intercept.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/s390/kvm/intercept.c
+++ b/arch/s390/kvm/intercept.c
@@ -199,7 +199,7 @@ static int handle_instruction_and_prog(s
 	return rc2;
 }
 
-static const intercept_handler_t intercept_funcs[0x48 >> 2] = {
+static const intercept_handler_t intercept_funcs[] = {
 	[0x00 >> 2] = handle_noop,
 	[0x04 >> 2] = handle_instruction,
 	[0x08 >> 2] = handle_prog,
@@ -216,7 +216,7 @@ int kvm_handle_sie_intercept(struct kvm_
 	intercept_handler_t func;
 	u8 code = vcpu->arch.sie_block->icptcode;
 
-	if (code & 3 || code > 0x48)
+	if (code & 3 || (code >> 2) >= ARRAY_SIZE(intercept_funcs))
 		return -ENOTSUPP;
 	func = intercept_funcs[code >> 2];
 	if (func)


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