[PATCH linux-next] xen/multicall: xen_mc_callback(): avoid buffer overflow

From: Tim Gardner
Date: Fri Feb 08 2013 - 15:35:08 EST


This buffer overflow was introduced with 91e0c5f3dad47838cb2ecc1865ce789a0b7182b1
(2.6.24).

Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: x86@xxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Tim Gardner <tim.gardner@xxxxxxxxxxxxx>
---

This patch applies cleanly to 3.1.10 and newer. Requires a backport
for 2.6.24-3.2.y

arch/x86/xen/multicalls.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/xen/multicalls.c b/arch/x86/xen/multicalls.c
index 0d82003..5270407 100644
--- a/arch/x86/xen/multicalls.c
+++ b/arch/x86/xen/multicalls.c
@@ -195,9 +195,10 @@ void xen_mc_callback(void (*fn)(void *), void *data)
struct mc_buffer *b = &__get_cpu_var(mc_buffer);
struct callback *cb;

- if (b->cbidx == MC_BATCH) {
+ if (b->cbidx >= MC_BATCH) {
trace_xen_mc_flush_reason(XEN_MC_FL_CALLBACK);
xen_mc_flush();
+ return;
}

trace_xen_mc_callback(fn, data);
--
1.7.9.5

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