mm/ksm: fix possible UAF of stable_node
The commit2c653d0ee2
("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@linux.dev Fixes:2c653d0ee2
("ksm: introduce ksm_max_page_sharing per page deduplication limit") Signed-off-by: Chengming Zhou <chengming.zhou@linux.dev> Acked-by: David Hildenbrand <david@redhat.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Hugh Dickins <hughd@google.com> Cc: Stefan Roesch <shr@devkernel.io> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
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mm/ksm.c
3
mm/ksm.c
@ -2153,7 +2153,6 @@ again:
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INIT_HLIST_HEAD(&stable_node_dup->hlist);
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stable_node_dup->kpfn = kpfn;
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folio_set_stable_node(kfolio, stable_node_dup);
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stable_node_dup->rmap_hlist_len = 0;
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DO_NUMA(stable_node_dup->nid = nid);
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if (!need_chain) {
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@ -2172,6 +2171,8 @@ again:
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stable_node_chain_add_dup(stable_node_dup, stable_node);
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}
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folio_set_stable_node(kfolio, stable_node_dup);
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return stable_node_dup;
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}
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