From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta1.migadu.com (out-235.mta1.migadu.com [95.215.58.235]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 77C263F0767 for ; Tue, 13 Oct 2026 02:17:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.235 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791857881; cv=none; b=delb1mghey6AzZyrdYErSeJAvbiI2gw4If92+a58VfIk384xU6YFxsLFztvexON0y1kwrIOcHT4dCN0zZk0NISz/It1PBaquA8I5+Ms/wficF2Ok8807jsyZMyqNkuncjKSb8KefohXRONnaNhUM7TzHoZV+Ivv9ADHI5gmvvKs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791857881; c=relaxed/simple; bh=jqBD77UOTyYWp8LQl19v9uNbH02DwyMcdp1Km7VJIyU=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=f4HqkipDYiSzKU4GExn2PyKpeReEr2GsIUQDS9LM2wPNmUqI4grByLYww3ww5EDbUWrsV2xeoq7c9Pqx23bNFX/mrKiqhb4QWxv86sySeRxchNVP76jU58EqJiptTqv8o8ozepNP1/M6Fs7Pe0crYGptuhs1QZvHbW1VpIgxsWI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=KlUKhBqT; arc=none smtp.client-ip=95.215.58.235 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="KlUKhBqT" X-Envelope-To: linux-kernel@vger.kernel.org DKIM-Signature: a=rsa-sha256; bh=jqBD77UOTyYWp8LQl19v9uNbH02DwyMcdp1Km7VJIyU=; c=simple/simple; d=linux.dev; h=from:to:subject:date:message-id:mime-version:content-type; s=key1; t=1791857875; v=1; x=1792462675; b=KlUKhBqTHE3cMyZVH8jSiitjq5XDDDcw5npLF/shy+ElifwoTmQ5o82dVY+c2NEVUybi8EJP z4b1r7PgpddjhiGuXjndBA5Sp5KMoz6Htm8/ful8el/7KKeQ9k3Sc/ElklqPEaaI9bpRLuFy8Vz tT0djsw8PRydg/b9wM+7vK4c= X-Envelope-To: linux-kernel@vger.kernel.org Received: by smtp.migadu.com with ESMTPS id 665a5cf49eac3c84; Tue, 13 Oct 2026 02:17:55 +0000 X-Mizu-Trace-ID: 665a5cf49eac3c84 X-Migadu-Flow: FLOW_OUT Message-ID: <103d5ab1-b9b5-4cf6-bf87-87771b91eea1@linux.dev> Date: Tue, 13 Oct 2026 10:17:47 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [syzbot] [mm?] possible deadlock in igrab To: Andrew Morton , syzbot Cc: david@fromorbit.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, muchun.song@linux.dev, roman.gushchin@linux.dev, syzkaller-bugs@googlegroups.com References: <6acd315b.8cdf6287.1eb53.0133.GAE@google.com> <20261012185640.5568805f927f4de127bf0f28@linux-foundation.org> From: Qi Zheng In-Reply-To: <20261012185640.5568805f927f4de127bf0f28@linux-foundation.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Hi Andrew, On 10/13/26 9:56 AM, Andrew Morton wrote: > On Mon, 12 Oct 2026 12:13:31 -0700 syzbot wrote: > >> Hello, >> >> syzbot found the following issue on: >> >> HEAD commit: b01868671970 Add linux-next specific files for 20261007 Looks like this doesn't include my latest fix patch in the testing. Fix patch: https://lore.kernel.org/all/20261011045956.30277-1-qi.zheng@linux.dev/ >> git tree: linux-next >> console output: https://syzkaller.appspot.com/x/log.txt?x=17ab503c580000 >> kernel config: https://syzkaller.appspot.com/x/.config?x=9ac1ab2cf2112eb1 >> dashboard link: https://syzkaller.appspot.com/bug?extid=9d97402eade2fc0c065c >> compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 >> >> Unfortunately, I don't have any reproducer for this issue yet. >> >> Downloadable assets: >> disk image: https://storage.googleapis.com/syzbot-assets/20420067bb60/disk-b0186867.raw.xz >> vmlinux: https://storage.googleapis.com/syzbot-assets/14149d837264/vmlinux-b0186867.xz >> kernel image: https://storage.googleapis.com/syzbot-assets/17346f8094aa/bzImage-b0186867.xz >> >> IMPORTANT: if you fix the issue, please add the following tag to the commit: >> Reported-by: syzbot+9d97402eade2fc0c065c@syzkaller.appspotmail.com >> >> ====================================================== >> WARNING: possible circular locking dependency detected >> syzkaller #0 Not tainted >> ------------------------------------------------------ > > Thanks. > > LLM firmly points at mm-stable's 743e7d025d2f ("mm: shmem: make unused > huge shrinker memcg aware"). > > This comes at an awkward time. The three patch series "make unused > huge shrinker memcg aware", v4 reverts cleanly so I'm inclined to do > that. > > If people can come up with a confident fix which we can upstream as a > hotfix during 7.4-rcX then maybe OK. Does the issue still reproduce after applying the fix patch above? Thanks, Qi > >> syz.5.203/6616 is trying to acquire lock: >> ffff88807e4d81e0 (&sb->s_type->i_lock_key){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:347 [inline] >> ffff88807e4d81e0 (&sb->s_type->i_lock_key){+.+.}-{3:3}, at: igrab+0xfb/0x2f0 fs/inode.c:1595 >> >> but task is already holding lock: >> ffff888062a65640 (&l->lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:347 [inline] >> ffff888062a65640 (&l->lock){+.+.}-{3:3}, at: lock_list_lru mm/list_lru.c:26 [inline] >> ffff888062a65640 (&l->lock){+.+.}-{3:3}, at: lock_list_lru_of_memcg+0x261/0x4c0 mm/list_lru.c:96 >> >> which lock already depends on the new lock. >> >> >> the existing dependency chain (in reverse order) is: >> >> -> #2 (&l->lock){+.+.}-{3:3}: >> __raw_spin_lock include/linux/spinlock_api_smp.h:190 [inline] >> _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:173 >> spin_lock include/linux/spinlock.h:347 [inline] >> lock_list_lru mm/list_lru.c:26 [inline] >> lock_list_lru_of_memcg+0x261/0x4c0 mm/list_lru.c:96 >> list_lru_lock mm/list_lru.c:156 [inline] >> list_lru_add+0x57/0x290 mm/list_lru.c:229 >> list_lru_add_obj+0x191/0x270 mm/list_lru.c:254 >> d_lru_add+0xd8/0x1a0 fs/dcache.c:522 >> retain_dentry fs/dcache.c:912 [inline] >> fast_dput+0x55c/0x690 fs/dcache.c:1005 >> dput+0x2b/0x60 fs/dcache.c:1054 >> path_put fs/namei.c:722 [inline] >> put_link+0x112/0x190 fs/namei.c:1201 >> walk_component fs/namei.c:2316 [inline] >> link_path_walk+0x12da/0x1910 fs/namei.c:2682 >> path_openat+0x1c4/0x1da0 fs/namei.c:5036 >> do_file_open+0x23e/0x4a0 fs/namei.c:5069 >> do_open_execat+0x12b/0x590 fs/exec.c:786 >> open_exec fs/exec.c:822 [inline] >> bprm_open_interpreter+0x85/0xb0 fs/exec.c:1455 >> load_elf_binary+0x1a5d/0x28d0 fs/binfmt_elf.c:904 >> search_binary_handler fs/exec.c:1777 [inline] >> exec_binprm fs/exec.c:1809 [inline] >> bprm_execve+0x930/0x1590 fs/exec.c:1865 >> kernel_execve+0x8af/0x9a0 fs/exec.c:2009 >> try_to_run_init_process+0x13/0x60 init/main.c:1489 >> kernel_init+0xb2/0x1d0 init/main.c:1619 >> ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 >> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 >> >> -> #1 (&lockref->lock){+.+.}-{3:3}: >> __raw_spin_lock include/linux/spinlock_api_smp.h:190 [inline] >> _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:173 >> spin_lock include/linux/spinlock.h:347 [inline] >> d_instantiate+0x72/0xb0 fs/dcache.c:2252 >> d_make_root+0x59/0x80 fs/dcache.c:2294 >> shmem_fill_super+0xcbc/0x1150 mm/shmem.c:5290 >> get_tree_super fs/super.c:1400 [inline] >> get_tree_nodev+0xbb/0x150 fs/super.c:1420 >> vfs_get_tree+0x92/0x2a0 fs/super.c:1943 >> fc_mount fs/namespace.c:1278 [inline] >> vfs_kern_mount+0x15b/0x220 fs/namespace.c:1316 >> kern_mount+0x43/0x90 fs/namespace.c:6500 >> shmem_init+0x37/0x170 mm/shmem.c:5610 >> mnt_init+0x19b/0x1f0 fs/namespace.c:6481 >> vfs_caches_init+0x22/0x30 fs/dcache.c:3686 >> start_kernel+0x351/0x3e0 init/main.c:1170 >> x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310 >> x86_64_start_kernel+0x137/0x1b0 arch/x86/kernel/head64.c:291 >> common_startup_64+0x13e/0x157 >> >> -> #0 (&sb->s_type->i_lock_key){+.+.}-{3:3}: >> check_prev_add kernel/locking/lockdep.c:3209 [inline] >> check_prevs_add kernel/locking/lockdep.c:3328 [inline] >> validate_chain kernel/locking/lockdep.c:3952 [inline] >> __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 >> lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 >> __raw_spin_lock include/linux/spinlock_api_smp.h:190 [inline] >> _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:173 >> spin_lock include/linux/spinlock.h:347 [inline] >> igrab+0xfb/0x2f0 fs/inode.c:1595 >> shmem_unused_huge_isolate+0x4f/0x290 mm/shmem.c:874 >> __list_lru_walk_one+0x171/0x440 mm/list_lru.c:362 >> list_lru_walk_one+0x3c/0x50 mm/list_lru.c:399 >> list_lru_shrink_walk include/linux/list_lru.h:332 [inline] >> shmem_unused_huge_shrink+0x173/0x1270 mm/shmem.c:966 >> super_cache_scan+0x411/0x4a0 fs/super.c:231 >> do_shrink_slab+0x6d0/0x10d0 mm/shrinker.c:445 >> shrink_slab_memcg mm/shrinker.c:562 [inline] >> shrink_slab+0x838/0x1210 mm/shrinker.c:640 >> drop_slab_node mm/vmscan.c:488 [inline] >> drop_slab+0x140/0x280 mm/vmscan.c:506 >> drop_caches_sysctl_handler+0xc7/0x170 fs/drop_caches.c:68 >> proc_sys_call_handler+0x4c1/0x830 fs/proc/proc_sysctl.c:600 >> do_iter_readv_writev+0x612/0x8c0 fs/read_write.c:-1 >> vfs_writev+0x343/0x990 fs/read_write.c:1058 >> do_writev+0x154/0x2e0 fs/read_write.c:1104 >> do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] >> do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> >> other info that might help us debug this: >> >> Chain exists of: >> &sb->s_type->i_lock_key --> &lockref->lock --> &l->lock >> >> Possible unsafe locking scenario: >> >> CPU0 CPU1 >> ---- ---- >> lock(&l->lock); >> lock(&lockref->lock); >> lock(&l->lock); >> lock(&sb->s_type->i_lock_key); >> >> *** DEADLOCK *** >> >> locks held by syz.5.203/6616: 5, last CPU#0: >> #0: ffff88807a2ef270 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x118/0x160 fs/file.c:1408 >> #1: ffff8880582de460 (sb_writers#3){.+.+}-{0:0}, at: file_start_write include/linux/fs.h:2756 [inline] >> #1: ffff8880582de460 (sb_writers#3){.+.+}-{0:0}, at: vfs_writev+0x2af/0x990 fs/read_write.c:1056 >> #2: ffff88807fe9e0e8 (&type->s_umount_key#56){++++}-{4:4}, at: super_trylock_shared fs/super.c:670 [inline] >> #2: ffff88807fe9e0e8 (&type->s_umount_key#56){++++}-{4:4}, at: super_cache_scan+0x94/0x4a0 fs/super.c:200 >> #3: ffff888062a65640 (&l->lock){+.+.}-{3:3}, at: spin_lock include/linux/spinlock.h:347 [inline] >> #3: ffff888062a65640 (&l->lock){+.+.}-{3:3}, at: lock_list_lru mm/list_lru.c:26 [inline] >> #3: ffff888062a65640 (&l->lock){+.+.}-{3:3}, at: lock_list_lru_of_memcg+0x261/0x4c0 mm/list_lru.c:96 >> #4: ffff88807e4d8018 (&info->lock){+.+.}-{3:3}, at: spin_trylock include/linux/spinlock.h:359 [inline] >> #4: ffff88807e4d8018 (&info->lock){+.+.}-{3:3}, at: shmem_unused_huge_isolate+0x26/0x290 mm/shmem.c:870 >> >> stack backtrace: >> CPU: 0 UID: 0 PID: 6616 Comm: syz.5.203 Not tainted syzkaller #0 PREEMPT(full) >> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026 >> Call Trace: >> >> dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 >> print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087 >> check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219 >> check_prev_add kernel/locking/lockdep.c:3209 [inline] >> check_prevs_add kernel/locking/lockdep.c:3328 [inline] >> validate_chain kernel/locking/lockdep.c:3952 [inline] >> __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288 >> lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942 >> __raw_spin_lock include/linux/spinlock_api_smp.h:190 [inline] >> _raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:173 >> spin_lock include/linux/spinlock.h:347 [inline] >> igrab+0xfb/0x2f0 fs/inode.c:1595 >> shmem_unused_huge_isolate+0x4f/0x290 mm/shmem.c:874 >> __list_lru_walk_one+0x171/0x440 mm/list_lru.c:362 >> list_lru_walk_one+0x3c/0x50 mm/list_lru.c:399 >> list_lru_shrink_walk include/linux/list_lru.h:332 [inline] >> shmem_unused_huge_shrink+0x173/0x1270 mm/shmem.c:966 >> super_cache_scan+0x411/0x4a0 fs/super.c:231 >> do_shrink_slab+0x6d0/0x10d0 mm/shrinker.c:445 >> shrink_slab_memcg mm/shrinker.c:562 [inline] >> shrink_slab+0x838/0x1210 mm/shrinker.c:640 >> drop_slab_node mm/vmscan.c:488 [inline] >> drop_slab+0x140/0x280 mm/vmscan.c:506 >> drop_caches_sysctl_handler+0xc7/0x170 fs/drop_caches.c:68 >> proc_sys_call_handler+0x4c1/0x830 fs/proc/proc_sysctl.c:600 >> do_iter_readv_writev+0x612/0x8c0 fs/read_write.c:-1 >> vfs_writev+0x343/0x990 fs/read_write.c:1058 >> do_writev+0x154/0x2e0 fs/read_write.c:1104 >> do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline] >> do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84 >> entry_SYSCALL_64_after_hwframe+0x77/0x7f >> RIP: 0033:0x7fe53d79e199 >> Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48 >> RSP: 002b:00007fe53e739028 EFLAGS: 00000246 ORIG_RAX: 0000000000000014 >> RAX: ffffffffffffffda RBX: 00007fe53da25fa0 RCX: 00007fe53d79e199 >> RDX: 0000000000000001 RSI: 00002000000000c0 RDI: 0000000000000004 >> RBP: 00007fe53d835888 R08: 0000000000000000 R09: 0000000000000000 >> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 >> R13: 00007fe53da26038 R14: 00007fe53da25fa0 R15: 00007ffc0e7c9828 >> >> syz.5.203 (6616): drop_caches: 2 >> >> >> --- >> This report is generated by a bot. It may contain errors. >> See https://goo.gl/tpsmEJ for more information about syzbot. >> syzbot engineers can be reached at syzkaller@googlegroups.com. >> >> syzbot will keep track of this issue. See: >> https://goo.gl/tpsmEJ#status for how to communicate with syzbot. >> >> If the report is already addressed, let syzbot know by replying with: >> #syz fix: exact-commit-title >> >> If you want to overwrite report's subsystems, reply with: >> #syz set subsystems: new-subsystem >> (See the list of subsystem names on the web dashboard) >> >> If the report is a duplicate of another one, reply with: >> #syz dup: exact-subject-of-another-report >> >> If you want to undo deduplication, reply with: >> #syz undup