FAILED: patch "[PATCH] mm: kfence: fix handling discontiguous page" failed to apply to 5.15-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 1f2803b2660f4b04d48d065072c0ae0c9ca255fd
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@xxxxxxxxxxxxxxx>' --in-reply-to '2023041153-figment-fanfare-e9c7@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^..

Possible dependencies:

1f2803b2660f ("mm: kfence: fix handling discontiguous page")
3ee2d7471fa4 ("mm: kfence: fix PG_slab and memcg_data clearing")
8f0b36497303 ("mm: kfence: fix objcgs vector allocation")
b33f778bba5e ("kfence: alloc kfence_pool after system startup")
698361bca2d5 ("kfence: allow re-enabling KFENCE after system startup")
07e8481d3c38 ("kfence: always use static branches to guard kfence_alloc()")
08f6b10630f2 ("kfence: limit currently covered allocations when pool nearly full")
a9ab52bbcb52 ("kfence: move saving stack trace of allocations into __kfence_alloc()")
9a19aeb56650 ("kfence: count unexpectedly skipped allocations")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 1f2803b2660f4b04d48d065072c0ae0c9ca255fd Mon Sep 17 00:00:00 2001
From: Muchun Song <muchun.song@xxxxxxxxx>
Date: Thu, 23 Mar 2023 10:50:03 +0800
Subject: [PATCH] mm: kfence: fix handling discontiguous page

The struct pages could be discontiguous when the kfence pool is allocated
via alloc_contig_pages() with CONFIG_SPARSEMEM and
!CONFIG_SPARSEMEM_VMEMMAP.

This may result in setting PG_slab and memcg_data to a arbitrary
address (may be not used as a struct page), which in the worst case
might corrupt the kernel.

So the iteration should use nth_page().

Link: https://lkml.kernel.org/r/20230323025003.94447-1-songmuchun@xxxxxxxxxxxxx
Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Reviewed-by: Kefeng Wang <wangkefeng.wang@xxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: SeongJae Park <sjpark@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>

diff --git a/mm/kfence/core.c b/mm/kfence/core.c
index d66092dd187c..1065e0568d05 100644
--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -556,7 +556,7 @@ static unsigned long kfence_init_pool(void)
 	 * enters __slab_free() slow-path.
 	 */
 	for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
-		struct slab *slab = page_slab(&pages[i]);
+		struct slab *slab = page_slab(nth_page(pages, i));
 
 		if (!i || (i % 2))
 			continue;
@@ -602,7 +602,7 @@ static unsigned long kfence_init_pool(void)
 
 reset_slab:
 	for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
-		struct slab *slab = page_slab(&pages[i]);
+		struct slab *slab = page_slab(nth_page(pages, i));
 
 		if (!i || (i % 2))
 			continue;