The patch titled
Subject: mm/ksm: fix possible UAF of stable_node
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
mm-ksm-fix-possible-uaf-of-stable_node.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-ksm-fix-possible-uaf-of-stable_node.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: Chengming Zhou <chengming.zhou@xxxxxxxxx>
Subject: mm/ksm: fix possible UAF of stable_node
Date: Mon, 13 May 2024 11:07:56 +0800
The commit 2c653d0ee2ae ("ksm: introduce ksm_max_page_sharing per page
deduplication limit") introduced a possible failure case in the
stable_tree_insert(), where we may free the new allocated stable_node_dup
if we fail to prepare the missing chain node.
Then that kfolio return and unlock with a freed stable_node set... And
any MM activities can come in to access kfolio->mapping, so UAF.
Fix it by moving folio_set_stable_node() to the end after stable_node
is inserted successfully.
Link: https://lkml.kernel.org/r/20240513-b4-ksm-stable-node-uaf-v1-1-f687de76f452@xxxxxxxxx
Fixes: 2c653d0ee2ae ("ksm: introduce ksm_max_page_sharing per page deduplication limit")
Signed-off-by: Chengming Zhou <chengming.zhou@xxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Stefan Roesch <shr@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/ksm.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/mm/ksm.c~mm-ksm-fix-possible-uaf-of-stable_node
+++ a/mm/ksm.c
@@ -2153,7 +2153,6 @@ again:
INIT_HLIST_HEAD(&stable_node_dup->hlist);
stable_node_dup->kpfn = kpfn;
- folio_set_stable_node(kfolio, stable_node_dup);
stable_node_dup->rmap_hlist_len = 0;
DO_NUMA(stable_node_dup->nid = nid);
if (!need_chain) {
@@ -2172,6 +2171,8 @@ again:
stable_node_chain_add_dup(stable_node_dup, stable_node);
}
+ folio_set_stable_node(kfolio, stable_node_dup);
+
return stable_node_dup;
}
_
Patches currently in -mm which might be from chengming.zhou@xxxxxxxxx are
mm-ksm-fix-possible-uaf-of-stable_node.patch
