[PATCH 1/2] LoongArch: KVM: EIOINTC: clamp ipnum to valid range in INT_ENCODE mode

[Tao Cui <cui.tao@linux.dev>]

From: Tao Cui <cuitao@kylinos.cn>

The IP-number decode in eiointc_set_sw_coreisr() and eiointc_update_irq()
clamps ipnum only in the default (1-hot) mode. In INT_ENCODE mode the raw
ipmap byte (0..255) is used as the index into sw_coreisr[cpu][ipnum],
whose second dimension is LOONGSON_IP_NUM (8), so any ipmap byte >= 8
accesses the array out of bounds.

The value is guest-programmable through the EIOINTC virtual extension
(VIRT_CONFIG enables INT_ENCODE and the IPMAP IOCSR write is unvalidated)
and is also restored unvalidated from a migration stream via the
LOAD_FINISHED control attribute, resulting in a host slab out-of-bounds
access reachable from an unprivileged guest.

Clamp ipnum to [0, LOONGSON_IP_NUM) in INT_ENCODE mode as well.

Fixes: 3956a52bc05b ("LoongArch: KVM: Add EIOINTC read and write functions")
Cc: stable@vger.kernel.org
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
---
 arch/loongarch/kvm/intc/eiointc.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/loongarch/kvm/intc/eiointc.c b/arch/loongarch/kvm/intc/eiointc.c
index 2b14485d14a7..0c34d7ab264d 100644
--- a/arch/loongarch/kvm/intc/eiointc.c
+++ b/arch/loongarch/kvm/intc/eiointc.c
@@ -17,6 +17,8 @@ static void eiointc_set_sw_coreisr(struct loongarch_eiointc *s)
 		if (!(s->status & BIT(EIOINTC_ENABLE_INT_ENCODE))) {
 			ipnum = count_trailing_zeros(ipnum);
 			ipnum = ipnum < 4 ? ipnum : 0;
+		} else {
+			ipnum = (ipnum < LOONGSON_IP_NUM) ? ipnum : 0;
 		}
 
 		cpuid = ((u8 *)s->coremap)[irq];
@@ -42,6 +44,8 @@ static void eiointc_update_irq(struct loongarch_eiointc *s, int irq, int level)
 	if (!(s->status & BIT(EIOINTC_ENABLE_INT_ENCODE))) {
 		ipnum = count_trailing_zeros(ipnum);
 		ipnum = ipnum < 4 ? ipnum : 0;
+	} else {
+		ipnum = (ipnum < LOONGSON_IP_NUM) ? ipnum : 0;
 	}
 
 	cpu = s->sw_coremap[irq];
-- 
2.43.0