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AJvYcCVEW3aNHQcjQ6+n0e9Lm1WVQxrXnwAvz2G4DY2oBd1NUjczlO2pgAkeVD86UEM7Tv8CIWIEzHT3NU9d6WM=@vger.kernel.org X-Gm-Message-State: AOJu0YxAYMiwCA95uHak4bEVLccm3f8ZzQyT10hi5iNHp4S7x6t68tH9 eWIrKl23SZ6ygBo2KvVbPZ6kVHJC2K7nJMc4ykGXoIW8uxrxXTBMMKYIfNlFKnd2CZGtIQMrRzk owTUVxlbaYW4N0ERXjbkaMt8F6rHc7u2csjOciWap3ph2aAt8yAKwMicGlxE= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:6684:b0:685:5300:f1ca with SMTP id 006d021491bc7-68be94cd315mr2177695eaf.64.1775877962645; Fri, 10 Apr 2026 20:26:02 -0700 (PDT) Date: Fri, 10 Apr 2026 20:26:02 -0700 In-Reply-To: <20260411031045.1713-1-hdanton@sina.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69d9bf4a.050a0220.3030df.003c.GAE@google.com> Subject: Re: [syzbot] [cgroups?] KASAN: slab-use-after-free Read in pressure_write From: syzbot To: hdanton@sina.com, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot has tested the proposed patch but the reproducer is still triggering an issue: possible deadlock in kernfs_drain_open_files ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.3.20/6665 is trying to acquire lock: ffffffff8df818f8 (drain_mutex){+.+.}-{4:4}, at: kernfs_drain_open_files+0x32/0x730 fs/kernfs/file.c:823 but task is already holding lock: ffffffff8de0ad98 (cgroup_mutex){+.+.}-{4:4}, at: cgroup_lock include/linux/cgroup.h:394 [inline] ffffffff8de0ad98 (cgroup_mutex){+.+.}-{4:4}, at: cgroup_kn_lock_live+0x13c/0x230 kernel/cgroup/cgroup.c:1732 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (cgroup_mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552 cgroup_lock include/linux/cgroup.h:394 [inline] cgroup_lock_and_drain_offline+0x8d/0x4a0 kernel/cgroup/cgroup.c:3265 cgroup_kn_lock_live+0x120/0x230 kernel/cgroup/cgroup.c:1730 cgroup_subtree_control_write+0x4b3/0x10a0 kernel/cgroup/cgroup.c:3580 cgroup_file_write+0x36f/0x790 kernel/cgroup/cgroup.c:4311 kernfs_fop_write_iter+0x3e4/0x580 fs/kernfs/file.c:357 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x629/0xba0 fs/read_write.c:688 ksys_write+0x156/0x270 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (&of->mutex){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552 kernfs_fop_write_iter+0x213/0x580 fs/kernfs/file.c:348 new_sync_write fs/read_write.c:595 [inline] vfs_write+0x629/0xba0 fs/read_write.c:688 ksys_write+0x156/0x270 fs/read_write.c:740 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #0 (drain_mutex){+.+.}-{4:4}: check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552 kernfs_drain_open_files+0x32/0x730 fs/kernfs/file.c:823 kernfs_drain+0x470/0x600 fs/kernfs/dir.c:542 __kernfs_remove+0x3cf/0x660 fs/kernfs/dir.c:1533 kernfs_remove_by_name_ns+0xaf/0x130 fs/kernfs/dir.c:1742 kernfs_remove_by_name include/linux/kernfs.h:641 [inline] cgroup_rm_file kernel/cgroup/cgroup.c:1758 [inline] cgroup_addrm_files+0x684/0xc30 kernel/cgroup/cgroup.c:4483 cgroup_destroy_locked+0x321/0x630 kernel/cgroup/cgroup.c:6197 cgroup_rmdir+0x3e8/0x710 kernel/cgroup/cgroup.c:6311 kernfs_iop_rmdir+0x203/0x350 fs/kernfs/dir.c:1311 vfs_rmdir+0x400/0x6f0 fs/namei.c:5344 filename_rmdir+0x292/0x520 fs/namei.c:5399 __do_sys_rmdir fs/namei.c:5422 [inline] __se_sys_rmdir+0x2e/0x140 fs/namei.c:5419 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f other info that might help us debug this: Chain exists of: drain_mutex --> &of->mutex --> cgroup_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(cgroup_mutex); lock(&of->mutex); lock(cgroup_mutex); lock(drain_mutex); *** DEADLOCK *** 4 locks held by syz.3.20/6665: #0: ffff88803bdc6480 (sb_writers#9){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493 #1: ffff888043d2ef78 (&type->i_mutex_dir_key#6/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1073 [inline] #1: ffff888043d2ef78 (&type->i_mutex_dir_key#6/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2929 [inline] #1: ffff888043d2ef78 (&type->i_mutex_dir_key#6/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2940 [inline] #1: ffff888043d2ef78 (&type->i_mutex_dir_key#6/1){+.+.}-{4:4}, at: filename_rmdir+0x1cd/0x520 fs/namei.c:5392 #2: ffff888043f66478 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: inode_lock include/linux/fs.h:1028 [inline] #2: ffff888043f66478 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: vfs_rmdir+0x109/0x6f0 fs/namei.c:5329 #3: ffffffff8de0ad98 (cgroup_mutex){+.+.}-{4:4}, at: cgroup_lock include/linux/cgroup.h:394 [inline] #3: ffffffff8de0ad98 (cgroup_mutex){+.+.}-{4:4}, at: cgroup_kn_lock_live+0x13c/0x230 kernel/cgroup/cgroup.c:1732 stack backtrace: CPU: 0 UID: 0 PID: 6665 Comm: syz.3.20 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043 check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175 check_prev_add kernel/locking/lockdep.c:3165 [inline] check_prevs_add kernel/locking/lockdep.c:3284 [inline] validate_chain kernel/locking/lockdep.c:3908 [inline] __lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237 lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868 __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552 kernfs_drain_open_files+0x32/0x730 fs/kernfs/file.c:823 kernfs_drain+0x470/0x600 fs/kernfs/dir.c:542 __kernfs_remove+0x3cf/0x660 fs/kernfs/dir.c:1533 kernfs_remove_by_name_ns+0xaf/0x130 fs/kernfs/dir.c:1742 kernfs_remove_by_name include/linux/kernfs.h:641 [inline] cgroup_rm_file kernel/cgroup/cgroup.c:1758 [inline] cgroup_addrm_files+0x684/0xc30 kernel/cgroup/cgroup.c:4483 cgroup_destroy_locked+0x321/0x630 kernel/cgroup/cgroup.c:6197 cgroup_rmdir+0x3e8/0x710 kernel/cgroup/cgroup.c:6311 kernfs_iop_rmdir+0x203/0x350 fs/kernfs/dir.c:1311 vfs_rmdir+0x400/0x6f0 fs/namei.c:5344 filename_rmdir+0x292/0x520 fs/namei.c:5399 __do_sys_rmdir fs/namei.c:5422 [inline] __se_sys_rmdir+0x2e/0x140 fs/namei.c:5419 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f178b75c819 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:00007f178adb6028 EFLAGS: 00000246 ORIG_RAX: 0000000000000054 RAX: ffffffffffffffda RBX: 00007f178b9d5fa0 RCX: 00007f178b75c819 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000100 RBP: 00007f178b7f2c91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f178b9d6038 R14: 00007f178b9d5fa0 R15: 00007fff5fda5b58 Tested on: commit: 7c6c4ed8 Merge tag 'vfs-7.0-rc8.fixes' of git://git.ke.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=141c7f4e580000 kernel config: https://syzkaller.appspot.com/x/.config?x=45cb3c58fd963c27 dashboard link: https://syzkaller.appspot.com/bug?extid=33e571025d88efd1312c compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 patch: https://syzkaller.appspot.com/x/patch.diff?x=169a1106580000