Patch "mm: kfence: fix PG_slab and memcg_data clearing" has been added to the 6.1-stable tree

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This is a note to let you know that I've just added the patch titled

    mm: kfence: fix PG_slab and memcg_data clearing

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mm-kfence-fix-pg_slab-and-memcg_data-clearing.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 3ee2d7471fa4963a2ced0a84f0653ce88b43c5b2 Mon Sep 17 00:00:00 2001
From: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Date: Mon, 20 Mar 2023 11:00:59 +0800
Subject: mm: kfence: fix PG_slab and memcg_data clearing

From: Muchun Song <songmuchun@xxxxxxxxxxxxx>

commit 3ee2d7471fa4963a2ced0a84f0653ce88b43c5b2 upstream.

It does not reset PG_slab and memcg_data when KFENCE fails to initialize
kfence pool at runtime.  It is reporting a "Bad page state" message when
kfence pool is freed to buddy.  The checking of whether it is a compound
head page seems unnecessary since we already guarantee this when
allocating kfence pool.   Remove the check to simplify the code.

Link: https://lkml.kernel.org/r/20230320030059.20189-1-songmuchun@xxxxxxxxxxxxx
Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: SeongJae Park <sjpark@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 mm/kfence/core.c |   30 +++++++++++++++---------------
 1 file changed, 15 insertions(+), 15 deletions(-)

--- a/mm/kfence/core.c
+++ b/mm/kfence/core.c
@@ -562,10 +562,6 @@ static unsigned long kfence_init_pool(vo
 		if (!i || (i % 2))
 			continue;
 
-		/* Verify we do not have a compound head page. */
-		if (WARN_ON(compound_head(&pages[i]) != &pages[i]))
-			return addr;
-
 		__folio_set_slab(slab_folio(slab));
 #ifdef CONFIG_MEMCG
 		slab->memcg_data = (unsigned long)&kfence_metadata[i / 2 - 1].objcg |
@@ -598,12 +594,26 @@ static unsigned long kfence_init_pool(vo
 
 		/* Protect the right redzone. */
 		if (unlikely(!kfence_protect(addr + PAGE_SIZE)))
-			return addr;
+			goto reset_slab;
 
 		addr += 2 * PAGE_SIZE;
 	}
 
 	return 0;
+
+reset_slab:
+	for (i = 0; i < KFENCE_POOL_SIZE / PAGE_SIZE; i++) {
+		struct slab *slab = page_slab(&pages[i]);
+
+		if (!i || (i % 2))
+			continue;
+#ifdef CONFIG_MEMCG
+		slab->memcg_data = 0;
+#endif
+		__folio_clear_slab(slab_folio(slab));
+	}
+
+	return addr;
 }
 
 static bool __init kfence_init_pool_early(void)
@@ -633,16 +643,6 @@ static bool __init kfence_init_pool_earl
 	 * fails for the first page, and therefore expect addr==__kfence_pool in
 	 * most failure cases.
 	 */
-	for (char *p = (char *)addr; p < __kfence_pool + KFENCE_POOL_SIZE; p += PAGE_SIZE) {
-		struct slab *slab = virt_to_slab(p);
-
-		if (!slab)
-			continue;
-#ifdef CONFIG_MEMCG
-		slab->memcg_data = 0;
-#endif
-		__folio_clear_slab(slab_folio(slab));
-	}
 	memblock_free_late(__pa(addr), KFENCE_POOL_SIZE - (addr - (unsigned long)__kfence_pool));
 	__kfence_pool = NULL;
 	return false;


Patches currently in stable-queue which might be from songmuchun@xxxxxxxxxxxxx are

queue-6.1/mm-kfence-fix-handling-discontiguous-page.patch
queue-6.1/mm-kfence-fix-pg_slab-and-memcg_data-clearing.patch



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