[PATCH v1 2/2] kho: unwind restored pages on kho_restore_vmalloc error

[Chenghao Duan]

In kho_restore_vmalloc(), when kho_restore_pages() succeeds, the
recovered pages are handed to the buddy allocator (via
adjust_managed_page_count()). If any later step (e.g.
__get_vm_area_node() or vmap_pages_range()) fails, the original error
path only called kvfree(pages), leaking those folio pages.

Fix by tracking how many folio groups have been restored with
restored_idx. On any failure, use err_unwind_restored to walk
restored_idx backwards and return each folio group to the buddy via
__free_pages() before freeing the pages array.

Signed-off-by: Chenghao Duan <duanchenghao at kylinos.cn>
---
 kernel/liveupdate/kexec_handover.c | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/kernel/liveupdate/kexec_handover.c b/kernel/liveupdate/kexec_handover.c
index ba03ff5baa9e..ed35405f59ab 100644
--- a/kernel/liveupdate/kexec_handover.c
+++ b/kernel/liveupdate/kexec_handover.c
@@ -1161,6 +1161,7 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
 	struct vm_struct *area;
 	struct page **pages;
 	unsigned int idx = 0;
+	unsigned int restored_idx = 0;
 	int err;
 
 	vm_flags = kho_flags_to_vmalloc(preservation->flags);
@@ -1183,11 +1184,11 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
 			phys_addr_t phys = chunk->phys[i];
 
 			if (idx + contig_pages > total_pages)
-				goto err_free_pages_array;
+				goto err_unwind_restored;
 
 			page = kho_restore_pages(phys, contig_pages);
 			if (!page)
-				goto err_free_pages_array;
+				goto err_unwind_restored;
 
 			for (int j = 0; j < contig_pages; j++)
 				pages[idx++] = page + j;
@@ -1195,13 +1196,14 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
 
 		page = kho_restore_pages(virt_to_phys(chunk), 1);
 		if (!page)
-			goto err_free_pages_array;
+			goto err_unwind_restored;
+		restored_idx = idx;
 		chunk = KHOSER_LOAD_PTR(chunk->hdr.next);
 		__free_page(page);
 	}
 
 	if (idx != total_pages)
-		goto err_free_pages_array;
+		goto err_unwind_restored;
 
 	area = __get_vm_area_node(total_pages * PAGE_SIZE, align, shift,
 				  vm_flags | VM_UNINITIALIZED,
@@ -1209,7 +1211,7 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
 				  NUMA_NO_NODE, GFP_KERNEL,
 				  __builtin_return_address(0));
 	if (!area)
-		goto err_free_pages_array;
+		goto err_unwind_restored;
 
 	addr = (unsigned long)area->addr;
 	size = get_vm_area_size(area);
@@ -1231,7 +1233,16 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
 
 err_free_vm_area:
 	free_vm_area(area);
-err_free_pages_array:
+err_unwind_restored:
+	/*
+	 * Pages already restored via kho_restore_pages() have been given to
+	 * the buddy allocator (via adjust_managed_page_count()). Return them
+	 * to the buddy so that failure leaves the system in a clean state.
+	 */
+	while (restored_idx > 0) {
+		restored_idx -= contig_pages;
+		__free_pages(pages[restored_idx], order);
+	}
 	kvfree(pages);
 	return NULL;
 }
-- 
2.25.1