+ mm-fix-use-after-free-bug-when-mm-mmap-is-reused-after-being-freed.patch added to -mm tree

+ mm-fix-use-after-free-bug-when-mm-mmap-is-reused-after-being-freed.patch added to -mm tree

[Andrew Morton]

The patch titled
     Subject: mm: fix use-after-free bug when mm->mmap is reused after being freed
has been added to the -mm tree.  Its filename is
     mm-fix-use-after-free-bug-when-mm-mmap-is-reused-after-being-freed.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-fix-use-after-free-bug-when-mm-mmap-is-reused-after-being-freed.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-fix-use-after-free-bug-when-mm-mmap-is-reused-after-being-freed.patch

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The -mm tree is included into linux-next and is updated
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------------------------------------------------------
From: Suren Baghdasaryan <surenb@google.com>
Subject: mm: fix use-after-free bug when mm->mmap is reused after being freed

After exit_mmap frees all vmas in the mm, mm->mmap needs to be reset,
otherwise it points to a vma that was freed and when reused leads to a
use-after-free bug.

Link: https://lore.kernel.org/all/00000000000072ef2c05d7f81950@google.com/
Link: https://lkml.kernel.org/r/20220215201922.1908156-1-surenb@google.com
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
Reported-by: syzbot+2ccf63a4bd07cf39cab0@syzkaller.appspotmail.com
Suggested-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Rik van Riel <riel@surriel.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <guro@fb.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Christian Brauner <christian.brauner@ubuntu.com>
Cc: Florian Weimer <fweimer@redhat.com>
Cc: Jan Engelhardt <jengelh@inai.de>
Cc: Tim Murray <timmurray@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/mmap.c |    1 +
 1 file changed, 1 insertion(+)

--- a/mm/mmap.c~mm-fix-use-after-free-bug-when-mm-mmap-is-reused-after-being-freed
+++ a/mm/mmap.c
@@ -3186,6 +3186,7 @@ void exit_mmap(struct mm_struct *mm)
 		vma = remove_vma(vma);
 		cond_resched();
 	}
+	mm->mmap = NULL;
 	mmap_write_unlock(mm);
 	vm_unacct_memory(nr_accounted);
 }
_

Patches currently in -mm which might be from surenb@google.com are

mm-fix-use-after-free-when-anon-vma-name-is-used-after-vma-is-freed.patch
mm-fix-use-after-free-bug-when-mm-mmap-is-reused-after-being-freed.patch