kho: fix out-of-bounds access of vmalloc chunk

The list of pages in a vmalloc chunk is NULL-terminated.  So when looping
through the pages in a vmalloc chunk, both kho_restore_vmalloc() and
kho_vmalloc_unpreserve_chunk() rightly make sure to stop when encountering
a NULL page.  But when the chunk is full, the loops do not stop and go
past the bounds of chunk->phys, resulting in out-of-bounds memory access,
and possibly the restoration or unpreservation of an invalid page.

Fix this by making sure the processing of chunk stops at the end of the
array.

Link: https://lkml.kernel.org/r/20251103110159.8399-1-pratyush@kernel.org
Fixes: a667300bd53f ("kho: add support for preserving vmalloc allocations")
Signed-off-by: Pratyush Yadav <pratyush@kernel.org>
Reviewed-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Cc: Alexander Graf <graf@amazon.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/kernel/kexec_handover.c b/kernel/kexec_handover.c
index 2a8c20c238a847e338c92fe036b8f8cd23ec720a..36fdce2667c5613d9a989a4195c36b9382873257 100644 (file)
--- a/kernel/kexec_handover.c
+++ b/kernel/kexec_handover.c
@@ -889,7 +889,7 @@ static void kho_vmalloc_unpreserve_chunk(struct kho_vmalloc_chunk *chunk)
 
        __kho_unpreserve(track, pfn, pfn + 1);
 
-       for (int i = 0; chunk->phys[i]; i++) {
+       for (int i = 0; i < ARRAY_SIZE(chunk->phys) && chunk->phys[i]; i++) {
                pfn = PHYS_PFN(chunk->phys[i]);
                __kho_unpreserve(track, pfn, pfn + 1);
        }
@@ -1012,7 +1012,7 @@ void *kho_restore_vmalloc(const struct kho_vmalloc *preservation)
        while (chunk) {
                struct page *page;
 
-               for (int i = 0; chunk->phys[i]; i++) {
+               for (int i = 0; i < ARRAY_SIZE(chunk->phys) && chunk->phys[i]; i++) {
                        phys_addr_t phys = chunk->phys[i];
 
                        if (idx + contig_pages > total_pages)