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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id n189-20020a8172c6000000b005771bb5a25dsm2391276ywc.61.2023.07.23.15.32.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 23 Jul 2023 15:32:34 -0700 (PDT) Date: Sun, 23 Jul 2023 15:32:27 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@ripple.attlocal.net To: Andrew Morton cc: Mike Kravetz , Mike Rapoport , "Kirill A. Shutemov" , Matthew Wilcox , David Hildenbrand , Suren Baghdasaryan , Qi Zheng , Yang Shi , Mel Gorman , Peter Xu , Peter Zijlstra , Will Deacon , Yu Zhao , Alistair Popple , Ralph Campbell , Ira Weiny , Steven Price , SeongJae Park , Lorenzo Stoakes , Huang Ying , Naoya Horiguchi , Christophe Leroy , Zack Rusin , Jason Gunthorpe , Axel Rasmussen , Anshuman Khandual , Pasha Tatashin , Miaohe Lin , Minchan Kim , Christoph Hellwig , Song Liu , Thomas Hellstrom , Russell King , "David S. Miller" , Michael Ellerman , "Aneesh Kumar K.V" , Heiko Carstens , Christian Borntraeger , Claudio Imbrenda , Alexander Gordeev , Gerald Schaefer , Vasily Gorbik , Jann Horn , Vishal Moola , Vlastimil Babka , Zi Yan , linux-arm-kernel@lists.infradead.org, sparclinux@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v3 10/13 fix] mm/khugepaged: collapse_pte_mapped_thp() with mmap_read_lock(): fix In-Reply-To: Message-ID: References: <7cd843a9-aa80-14f-5eb2-33427363c20@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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@syzkaller.appspotmail.com Closes: https://lore.kernel.org/lkml/000000000000f9de430600ae05db@google.com/ Reported-by: syzbot+173cc8cfdfbbef6dd755@syzkaller.appspotmail.com Closes: https://lore.kernel.org/linux-mm/000000000000e4b0f0060123ca40@google.com/ Signed-off-by: Hugh Dickins --- 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