linux-kernel - Re: [PATCH v3 1/1] mm: fix use-after-free when anon vma name is used after vma is freed

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Date:   Tue, 15 Feb 2022 20:47:55 +0100
From:   Michal Hocko <mhocko@...e.com>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     akpm@...ux-foundation.org, ccross@...gle.com,
        sumit.semwal@...aro.org, dave.hansen@...el.com,
        keescook@...omium.org, willy@...radead.org,
        kirill.shutemov@...ux.intel.com, vbabka@...e.cz,
        hannes@...xchg.org, ebiederm@...ssion.com, brauner@...nel.org,
        legion@...nel.org, ran.xiaokai@....com.cn, sashal@...nel.org,
        chris.hyser@...cle.com, dave@...olabs.net, pcc@...gle.com,
        caoxiaofeng@...ong.com, david@...hat.com, gorcunov@...il.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com,
        syzbot+aa7b3d4b35f9dc46a366@...kaller.appspotmail.com
Subject: Re: [PATCH v3 1/1] mm: fix use-after-free when anon vma name is used
 after vma is freed

Forgot to include one hunk:

diff --git a/include/linux/mm_inline.h b/include/linux/mm_inline.h
index cff619f762d0..17c20597e244 100644
--- a/include/linux/mm_inline.h
+++ b/include/linux/mm_inline.h
@@ -175,6 +175,11 @@ static inline void free_vma_anon_name(struct vm_area_struct *vma)
 	anon_vma_name_put(vma->anon_name);
 }
 
+static inline void dup_vma_anon_name(struct vm_area_struct *vma)
+{
+	anon_vma_name_get(vma->anon_name);
+}
+
 #else /* CONFIG_ANON_VMA_NAME */
 static inline const char *vma_anon_name(struct vm_area_struct *vma)
 {
@@ -187,6 +192,9 @@ static inline bool anon_vma_name_eq(struct anon_vma_name *name1, struct anon_vma
 static inline void free_vma_anon_name(struct vm_area_struct *vma)
 {
 }
+static inline void dup_vma_anon_name(struct vm_area_struct *vma)
+{
+}
 #endif  /* CONFIG_ANON_VMA_NAME */
 
 static inline void init_tlb_flush_pending(struct mm_struct *mm)
diff --git a/kernel/fork.c b/kernel/fork.c
index d75a528f7b21..dee514488003 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -366,7 +366,7 @@ struct vm_area_struct *vm_area_dup(struct vm_area_struct *orig)
 		*new = data_race(*orig);
 		INIT_LIST_HEAD(&new->anon_vma_chain);
 		new->vm_next = new->vm_prev = NULL;
-		dup_vma_anon_name(orig, new);
+		dup_vma_anon_name(new);
 	}
 	return new;
 }
-- 
Michal Hocko
SUSE Labs