| Message ID | 20180712154152.32183-2-peter.maydell@linaro.org |
|---|---|
| State | New |
| Headers | show |
| Series | a couple of GICv2 bug fixes | expand |
On 07/12/2018 10:41 AM, Peter Maydell wrote: > In gic_deactivate_irq() the interrupt number comes from the guest > (on a write to the GICC_DIR register), so we need to sanity check > that it isn't out of range before we use it as an array index. > Handle this in a similar manner to the check we do in > gic_complete_irq() for the GICC_EOI register. > > The array overrun is not disastrous because the calling code > uses (value & 0x3ff) to extract the interrupt field, so the > only out-of-range values possible are 1020..1023, which allow > overrunning only from irq_state[] into the following > irq_target[] array which the guest can already manipulate. > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- > hw/intc/arm_gic.c | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) Reviewed-by: Richard Henderson <richard.henderson@linaro.org> r~
On 07/12/2018 05:41 PM, Peter Maydell wrote: > In gic_deactivate_irq() the interrupt number comes from the guest > (on a write to the GICC_DIR register), so we need to sanity check > that it isn't out of range before we use it as an array index. > Handle this in a similar manner to the check we do in > gic_complete_irq() for the GICC_EOI register. > > The array overrun is not disastrous because the calling code > uses (value & 0x3ff) to extract the interrupt field, so the > only out-of-range values possible are 1020..1023, which allow > overrunning only from irq_state[] into the following > irq_target[] array which the guest can already manipulate. > > Signed-off-by: Peter Maydell <peter.maydell@linaro.org> > --- > hw/intc/arm_gic.c | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) Reviewed-by: Luc Michel <luc.michel@greensocs.com>
diff --git a/hw/intc/arm_gic.c b/hw/intc/arm_gic.c index ea0323f9691..b0a69d6386e 100644 --- a/hw/intc/arm_gic.c +++ b/hw/intc/arm_gic.c @@ -543,7 +543,21 @@ static bool gic_eoi_split(GICState *s, int cpu, MemTxAttrs attrs) static void gic_deactivate_irq(GICState *s, int cpu, int irq, MemTxAttrs attrs) { int cm = 1 << cpu; - int group = gic_has_groups(s) && GIC_TEST_GROUP(irq, cm); + int group; + + if (irq >= s->num_irq) { + /* + * This handles two cases: + * 1. If software writes the ID of a spurious interrupt [ie 1023] + * to the GICC_DIR, the GIC ignores that write. + * 2. If software writes the number of a non-existent interrupt + * this must be a subcase of "value written is not an active interrupt" + * and so this is UNPREDICTABLE. We choose to ignore it. + */ + return; + } + + group = gic_has_groups(s) && GIC_TEST_GROUP(irq, cm); if (!gic_eoi_split(s, cpu, attrs)) { /* This is UNPREDICTABLE; we choose to ignore it */
In gic_deactivate_irq() the interrupt number comes from the guest (on a write to the GICC_DIR register), so we need to sanity check that it isn't out of range before we use it as an array index. Handle this in a similar manner to the check we do in gic_complete_irq() for the GICC_EOI register. The array overrun is not disastrous because the calling code uses (value & 0x3ff) to extract the interrupt field, so the only out-of-range values possible are 1020..1023, which allow overrunning only from irq_state[] into the following irq_target[] array which the guest can already manipulate. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> --- hw/intc/arm_gic.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-)