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Sat, 12 Nov 2022 04:01:33 +0000 (UTC) X-FDA: 80123440866.03.385C9D9 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by imf15.hostedemail.com (Postfix) with ESMTP id BF46EA0007 for ; Sat, 12 Nov 2022 04:01:30 +0000 (UTC) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.57]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4N8MHd1XlXzJnb2; Sat, 12 Nov 2022 11:58:21 +0800 (CST) Received: from [10.174.151.185] (10.174.151.185) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Sat, 12 Nov 2022 12:01:24 +0800 From: Miaohe Lin Subject: Re: [syzbot] possible deadlock in hugetlb_fault To: Mike Kravetz , syzbot CC: , , , , , , , , References: <0000000000008c742d05eca72d4d@google.com> Message-ID: Date: Sat, 12 Nov 2022 12:01:24 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.151.185] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=none; spf=pass (imf15.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.189 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1668225692; a=rsa-sha256; cv=none; b=ZKzMXtFNmk25YjLkJTTDyDLGqWUGNzjMHmjTq0W63sT1V3GLeT/nbc1nKoVb7ulpTni11F i0AX+eN6fMQUL7hQ6QrhWVe8Oki+eYY6xpub9HRIyAcP2VseDzaiGb10TuJCpDQBSJuALp CR2ppH8B0IIwsm16UQsWs7qQ9iql9gg= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1668225692; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=pm2JSeBNiVnOqYLOQrWKJEO/+7K5SFv2DZ3Oej5vQVc=; b=f8g7mrceJM1RXkoD0zzgXX4TZq8Pq99uOTFEvsVSRyGvHLPLKKojpHcZx0lcbDPFPm8oXe DsuSfCTJxM/MeYPkU06Lq+eL4eMoHDP8TbhDN/jFS/k7Mx/2+vuHbhl4AY3Z0NsO1c4x+H qf2GieTPRRcgbfPD6yh6d8LYsDN2eWI= X-Rspam-User: Authentication-Results: imf15.hostedemail.com; dkim=none; spf=pass (imf15.hostedemail.com: domain of linmiaohe@huawei.com designates 45.249.212.189 as permitted sender) smtp.mailfrom=linmiaohe@huawei.com; dmarc=pass (policy=quarantine) header.from=huawei.com X-Stat-Signature: w5qjniiopdx5i11rqm7de65d5qqej6s9 X-Rspamd-Queue-Id: BF46EA0007 X-Rspamd-Server: rspam09 X-HE-Tag: 1668225690-453231 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2022/11/12 8:07, Mike Kravetz wrote: > On 11/04/22 09:00, syzbot wrote: >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: f2f32f8af2b0 Merge tag 'for-6.1-rc3-tag' of git://git.kern.. >> git tree: upstream >> console output: https://syzkaller.appspot.com/x/log.txt?x=137d52ca880000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=d080a4bd239918dd >> dashboard link: https://syzkaller.appspot.com/bug?extid=ca56f14c500045350f93 >> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 >> userspace arch: i386 >> >> Unfortunately, I don't have any reproducer for this issue yet. >> >> Downloadable assets: >> disk image: https://storage.googleapis.com/syzbot-assets/b4f72e7a4c11/disk-f2f32f8a.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/3f88997ad7c9/vmlinux-f2f32f8a.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/b4b5b3963e2d/bzImage-f2f32f8a.xz >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+ca56f14c500045350f93@syzkaller.appspotmail.com >> >> ====================================================== >> WARNING: possible circular locking dependency detected >> 6.1.0-rc3-syzkaller-00152-gf2f32f8af2b0 #0 Not tainted >> ------------------------------------------------------ >> syz-executor.2/5665 is trying to acquire lock: >> ffff88801c74c298 (&mm->mmap_lock#2){++++}-{3:3}, at: __might_fault+0xa1/0x170 mm/memory.c:5645 >> >> but task is already holding lock: >> ffff88801c4f3078 (&vma_lock->rw_sema){++++}-{3:3}, at: hugetlb_vma_lock_read mm/hugetlb.c:6816 [inline] >> ffff88801c4f3078 (&vma_lock->rw_sema){++++}-{3:3}, at: hugetlb_fault+0x40a/0x2060 mm/hugetlb.c:5859 >> >> which lock already depends on the new lock. >> >> >> the existing dependency chain (in reverse order) is: >> >> -> #1 (&vma_lock->rw_sema){++++}-{3:3}: >> down_write+0x90/0x220 kernel/locking/rwsem.c:1562 >> hugetlb_vma_lock_write mm/hugetlb.c:6834 [inline] >> __unmap_hugepage_range_final+0x97/0x340 mm/hugetlb.c:5202 >> unmap_single_vma+0x23d/0x2a0 mm/memory.c:1690 >> unmap_vmas+0x21e/0x370 mm/memory.c:1733 >> exit_mmap+0x189/0x7a0 mm/mmap.c:3090 >> __mmput+0x128/0x4c0 kernel/fork.c:1185 >> mmput+0x5c/0x70 kernel/fork.c:1207 >> exit_mm kernel/exit.c:516 [inline] >> do_exit+0xa39/0x2a20 kernel/exit.c:807 >> do_group_exit+0xd0/0x2a0 kernel/exit.c:950 >> get_signal+0x21a1/0x2430 kernel/signal.c:2858 >> arch_do_signal_or_restart+0x82/0x2300 arch/x86/kernel/signal.c:869 >> exit_to_user_mode_loop kernel/entry/common.c:168 [inline] >> exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:203 >> __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] >> syscall_exit_to_user_mode+0x19/0x50 kernel/entry/common.c:296 >> __do_fast_syscall_32+0x72/0xf0 arch/x86/entry/common.c:181 >> do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203 >> entry_SYSENTER_compat_after_hwframe+0x70/0x82 >> >> -> #0 (&mm->mmap_lock#2){++++}-{3:3}: >> check_prev_add kernel/locking/lockdep.c:3097 [inline] >> check_prevs_add kernel/locking/lockdep.c:3216 [inline] >> validate_chain kernel/locking/lockdep.c:3831 [inline] >> __lock_acquire+0x2a43/0x56d0 kernel/locking/lockdep.c:5055 >> lock_acquire kernel/locking/lockdep.c:5668 [inline] >> lock_acquire+0x1df/0x630 kernel/locking/lockdep.c:5633 >> __might_fault mm/memory.c:5646 [inline] >> __might_fault+0x104/0x170 mm/memory.c:5639 >> _copy_from_user+0x25/0x170 lib/usercopy.c:13 >> copy_from_user include/linux/uaccess.h:161 [inline] >> snd_rawmidi_kernel_write1+0x366/0x880 sound/core/rawmidi.c:1549 >> snd_rawmidi_write+0x273/0xbb0 sound/core/rawmidi.c:1618 >> vfs_write+0x2d7/0xdd0 fs/read_write.c:582 >> ksys_write+0x1e8/0x250 fs/read_write.c:637 >> do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline] >> __do_fast_syscall_32+0x65/0xf0 arch/x86/entry/common.c:178 >> do_fast_syscall_32+0x2f/0x70 arch/x86/entry/common.c:203 >> entry_SYSENTER_compat_after_hwframe+0x70/0x82 >> >> other info that might help us debug this: >> >> Possible unsafe locking scenario: >> >> CPU0 CPU1 >> ---- ---- >> lock(&vma_lock->rw_sema); >> lock(&mm->mmap_lock#2); >> lock(&vma_lock->rw_sema); >> lock(&mm->mmap_lock#2); > > I may not be reading the report correctly, but I can not see how we acquire the > hugetlb vma_lock before trying to acquire mmap_lock in stack 0. We would not > acquire the vma_lock until we enter hugetlb fault processing (not in the stack). > > Adding Miaohe Lin on Cc due to previous help with vma_lock potential deadlock > situations. Miaohe, does this make sense to you? > Hi Mike, This doesn't make sense for me too. Stack #1 shows that syz-executor is releasing its address space while stack #0 shows another thread is serving the write syscall. In this case, mm->mm_users is 0 and all threads in this process should be serving do_exit()? But I could be easily wrong. Also I can't see how vma_lock is locked before trying to acquire mmap_lock in above stacks. Might this be a false positive? Thanks, Miaohe Lin