[PATCH v2 1/2] KVM: arm64: Fix potential leak in hyp_trace_buffer_alloc_bpages_backing

[Vincent Donnefort]

In the very unlikely event of a failure in __map_hyp, the allocated
backing pages are leaked in hyp_trace_buffer_alloc_bpages_backing(). Fix
this by freeing the pages on error.

Fixes: 3aed038aac8d ("KVM: arm64: Add trace remote for the nVHE/pKVM hyp")
Reported-by: Sashiko <sashiko-bot at kernel.org>
Reviewed-by: Fuad Tabba <fuad.tabba at linux.dev>
Tested-by: Fuad Tabba <fuad.tabba at linux.dev>
Signed-off-by: Vincent Donnefort <vdonnefort at google.com>

diff --git a/arch/arm64/kvm/hyp_trace.c b/arch/arm64/kvm/hyp_trace.c
index 2411b4c32932..a7237aca6898 100644
--- a/arch/arm64/kvm/hyp_trace.c
+++ b/arch/arm64/kvm/hyp_trace.c
@@ -160,6 +160,7 @@ static int hyp_trace_buffer_alloc_bpages_backing(struct hyp_trace_buffer *trace_
 	int nr_bpages = (PAGE_ALIGN(size) / PAGE_SIZE) + 1;
 	size_t backing_size;
 	void *start;
+	int ret;
 
 	backing_size = PAGE_ALIGN(sizeof(struct simple_buffer_page) * nr_bpages *
 				  num_possible_cpus());
@@ -168,10 +169,16 @@ static int hyp_trace_buffer_alloc_bpages_backing(struct hyp_trace_buffer *trace_
 	if (!start)
 		return -ENOMEM;
 
+	ret = __map_hyp(start, backing_size);
+	if (ret) {
+		free_pages_exact(start, backing_size);
+		return ret;
+	}
+
 	trace_buffer->desc->bpages_backing_start = (unsigned long)start;
 	trace_buffer->desc->bpages_backing_size = backing_size;
 
-	return __map_hyp(start, backing_size);
+	return ret;
 }
 
 static void hyp_trace_buffer_free_bpages_backing(struct hyp_trace_buffer *trace_buffer)
-- 
2.55.0.795.g602f6c329a-goog