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[2003:cb:c706:5b00:c9f4:7535:9360:70d7]) by smtp.gmail.com with ESMTPSA id m17-20020a056000009100b0022eafed36ebsm5567280wrx.73.2022.10.26.07.46.20 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 26 Oct 2022 07:46:20 -0700 (PDT) Message-ID: Date: Wed, 26 Oct 2022 16:46:19 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.1 Subject: Re: [syzbot] WARNING in __split_huge_page_tail Content-Language: en-US To: Dmitry Vyukov Cc: syzbot , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, Mel Gorman , Hugh Dickins References: <000000000000aa2b2805ebea9137@google.com> <9a450a11-531d-8e1a-4c77-70102aa7f424@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 26.10.22 15:25, Dmitry Vyukov wrote: > On Wed, 26 Oct 2022 at 02:54, David Hildenbrand wrote: >> >> On 26.10.22 08:59, syzbot wrote: >>> Hello, >>> >>> syzbot found the following issue on: >>> >>> HEAD commit: 4da34b7d175d Merge tag 'thermal-6.1-rc2' of git://git.kern.. >>> git tree: upstream >>> console+strace: https://syzkaller.appspot.com/x/log.txt?x=113bd8bc880000 >>> kernel config: https://syzkaller.appspot.com/x/.config?x=4789759e8a6d5f57 >>> dashboard link: https://syzkaller.appspot.com/bug?extid=273b547b15eb58ea35e8 >>> compiler: Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2 >>> syz repro: https://syzkaller.appspot.com/x/repro.syz?x=161e1f62880000 >>> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16dd4fe6880000 >>> >>> Downloadable assets: >>> disk image: https://storage.googleapis.com/syzbot-assets/a61ddb36c296/disk-4da34b7d.raw.xz >>> vmlinux: https://storage.googleapis.com/syzbot-assets/ceee41246252/vmlinux-4da34b7d.xz >>> >>> IMPORTANT: if you fix the issue, please add the following tag to the commit: >>> Reported-by: syzbot+273b547b15eb58ea35e8@syzkaller.appspotmail.com >>> >>> tlb_finish_mmu+0xcb/0x200 mm/mmu_gather.c:363 >>> exit_mmap+0x2b1/0x670 mm/mmap.c:3098 >>> __mmput+0x114/0x3b0 kernel/fork.c:1185 >>> exit_mm+0x217/0x2f0 kernel/exit.c:516 >>> do_exit+0x5e7/0x2070 kernel/exit.c:807 >>> do_group_exit+0x1fd/0x2b0 kernel/exit.c:950 >>> __do_sys_exit_group kernel/exit.c:961 [inline] >>> __se_sys_exit_group kernel/exit.c:959 [inline] >>> __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:959 >>> do_syscall_x64 arch/x86/entry/common.c:50 [inline] >>> do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80 >>> entry_SYSCALL_64_after_hwframe+0x63/0xcd >>> ------------[ cut here ]------------ >>> WARNING: CPU: 0 PID: 3908 at mm/huge_memory.c:2465 __split_huge_page_tail+0x81c/0x1080 mm/huge_memory.c:2465 >> >> Is this the >> >> VM_BUG_ON_PAGE(atomic_read(&page_tail->_mapcount) != -1, page_tail); >> >> assertion? > > Hi David, > > You can check the sources for that revision, but on the dashboard > there are clickable links for all source references: > https://syzkaller.appspot.com/bug?extid=273b547b15eb58ea35e8 > > In this case it points to: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/mm/huge_memory.c?id=4da34b7d175dc99b8befebd69e96546c960d526c#n2465 > Ah, thanks! ... so if (!folio_test_swapcache(page_folio(head))) { VM_WARN_ON_ONCE_PAGE(page_tail->private != 0, head); page_tail->private = 0; } I recall that there was a patch either from Hugh or Mel floating around that might be related. -- Thanks, David / dhildenb