Patch "riscv: kvm: Fix out-of-bounds array access" has been added to the 6.12-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    riscv: kvm: Fix out-of-bounds array access

to the 6.12-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     riscv-kvm-fix-out-of-bounds-array-access.patch
and it can be found in the queue-6.12 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 27425e1a5b69d644e293d89607553287c0aa4df5
Author: Björn Töpel <bjorn@xxxxxxxxxxxx>
Date:   Mon Nov 4 20:15:01 2024 +0100

    riscv: kvm: Fix out-of-bounds array access
    
    [ Upstream commit 332fa4a802b16ccb727199da685294f85f9880cb ]
    
    In kvm_riscv_vcpu_sbi_init() the entry->ext_idx can contain an
    out-of-bound index. This is used as a special marker for the base
    extensions, that cannot be disabled. However, when traversing the
    extensions, that special marker is not checked prior indexing the
    array.
    
    Add an out-of-bounds check to the function.
    
    Fixes: 56d8a385b605 ("RISC-V: KVM: Allow some SBI extensions to be disabled by default")
    Signed-off-by: Björn Töpel <bjorn@xxxxxxxxxxxx>
    Reviewed-by: Anup Patel <anup@xxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20241104191503.74725-1-bjorn@xxxxxxxxxx
    Signed-off-by: Anup Patel <anup@xxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
index 7de128be8db9b..6e704ed86a83a 100644
--- a/arch/riscv/kvm/vcpu_sbi.c
+++ b/arch/riscv/kvm/vcpu_sbi.c
@@ -486,19 +486,22 @@ void kvm_riscv_vcpu_sbi_init(struct kvm_vcpu *vcpu)
 	struct kvm_vcpu_sbi_context *scontext = &vcpu->arch.sbi_context;
 	const struct kvm_riscv_sbi_extension_entry *entry;
 	const struct kvm_vcpu_sbi_extension *ext;
-	int i;
+	int idx, i;
 
 	for (i = 0; i < ARRAY_SIZE(sbi_ext); i++) {
 		entry = &sbi_ext[i];
 		ext = entry->ext_ptr;
+		idx = entry->ext_idx;
+
+		if (idx < 0 || idx >= ARRAY_SIZE(scontext->ext_status))
+			continue;
 
 		if (ext->probe && !ext->probe(vcpu)) {
-			scontext->ext_status[entry->ext_idx] =
-				KVM_RISCV_SBI_EXT_STATUS_UNAVAILABLE;
+			scontext->ext_status[idx] = KVM_RISCV_SBI_EXT_STATUS_UNAVAILABLE;
 			continue;
 		}
 
-		scontext->ext_status[entry->ext_idx] = ext->default_disabled ?
+		scontext->ext_status[idx] = ext->default_disabled ?
 					KVM_RISCV_SBI_EXT_STATUS_DISABLED :
 					KVM_RISCV_SBI_EXT_STATUS_ENABLED;
 	}