+ kho-fix-out-of-bounds-access-of-vmalloc-chunk.patch added to mm-hotfixes-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: kho: fix out-of-bounds access of vmalloc chunk
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     kho-fix-out-of-bounds-access-of-vmalloc-chunk.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kho-fix-out-of-bounds-access-of-vmalloc-chunk.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Pratyush Yadav <pratyush@kernel.org>
Subject: kho: fix out-of-bounds access of vmalloc chunk
Date: Mon, 3 Nov 2025 12:01:57 +0100

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: a667300bd53f2 ("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>
---

 kernel/kexec_handover.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/kexec_handover.c~kho-fix-out-of-bounds-access-of-vmalloc-chunk
+++ a/kernel/kexec_handover.c
@@ -889,7 +889,7 @@ static void kho_vmalloc_unpreserve_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 k
 	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)
_

Patches currently in -mm which might be from pratyush@kernel.org are

kho-fix-out-of-bounds-access-of-vmalloc-chunk.patch
kho-fix-unpreservation-of-higher-order-vmalloc-preservations.patch
kho-warn-and-exit-when-unpreserved-page-wasnt-preserved.patch