linux-kernel - [PATCH v3 10/13 fix] mm/khugepaged: collapse_pte_mapped_thp() with mmap_read

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <d3d9ff14-ef8-8f84-e160-bfa1f5794275@google.com>
Date:   Sun, 23 Jul 2023 15:32:27 -0700 (PDT)
From:   Hugh Dickins <hughd@...gle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
cc:     Mike Kravetz <mike.kravetz@...cle.com>,
        Mike Rapoport <rppt@...nel.org>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Matthew Wilcox <willy@...radead.org>,
        David Hildenbrand <david@...hat.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Qi Zheng <zhengqi.arch@...edance.com>,
        Yang Shi <shy828301@...il.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Peter Xu <peterx@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Will Deacon <will@...nel.org>, Yu Zhao <yuzhao@...gle.com>,
        Alistair Popple <apopple@...dia.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Ira Weiny <ira.weiny@...el.com>,
        Steven Price <steven.price@....com>,
        SeongJae Park <sj@...nel.org>,
        Lorenzo Stoakes <lstoakes@...il.com>,
        Huang Ying <ying.huang@...el.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Zack Rusin <zackr@...are.com>, Jason Gunthorpe <jgg@...pe.ca>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Pasha Tatashin <pasha.tatashin@...een.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Minchan Kim <minchan@...nel.org>,
        Christoph Hellwig <hch@...radead.org>,
        Song Liu <song@...nel.org>,
        Thomas Hellstrom <thomas.hellstrom@...ux.intel.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Michael Ellerman <mpe@...erman.id.au>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Heiko Carstens <hca@...ux.ibm.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Alexander Gordeev <agordeev@...ux.ibm.com>,
        Gerald Schaefer <gerald.schaefer@...ux.ibm.com>,
        Vasily Gorbik <gor@...ux.ibm.com>,
        Jann Horn <jannh@...gle.com>,
        Vishal Moola <vishal.moola@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>, Zi Yan <ziy@...dia.com>,
        linux-arm-kernel@...ts.infradead.org, sparclinux@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH v3 10/13 fix] mm/khugepaged: collapse_pte_mapped_thp() with
 mmap_read_lock(): fix

madvise_collapse() setting "mmap_locked = true" after calling
collapse_pte_mapped_thp() looked good but was wrong.  If the loop then
moves on to the next extent, mmap_locked assures it that "vma" has been
revalidated under mmap_lock, which was not the case: and led to UAFs,
crashes in __fput() or task_work_run(), even collapse_file()'s
VM_BUG_ON(start & (HPAGE_PMD_NR - 1)) - all detected by syzbot.

(collapse_pte_mapped_thp() does validate the vma that it works on:
but it's not passed in as an argument, collapse_pte_mapped_thp() finds
the vma for mm and addr by itself - which may by this time have changed
from the vma saved in madvise_collapse().)

Reported-by: syzbot+fe7b1487405295d29268@...kaller.appspotmail.com
Closes: https://lore.kernel.org/lkml/000000000000f9de430600ae05db@google.com/
Reported-by: syzbot+173cc8cfdfbbef6dd755@...kaller.appspotmail.com
Closes: https://lore.kernel.org/linux-mm/000000000000e4b0f0060123ca40@google.com/
Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
 mm/khugepaged.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 6bad69c0e4bd..1c773db26e88 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -2747,7 +2747,7 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev,
 			BUG_ON(*prev);
 			mmap_read_lock(mm);
 			result = collapse_pte_mapped_thp(mm, addr, true);
-			mmap_locked = true;
+			mmap_read_unlock(mm);
 			goto handle_result;
 		/* Whitelisted set of results where continuing OK */
 		case SCAN_PMD_NULL:
-- 
2.35.3