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006d021491bc7-68a63c8a4b3mr1761649eaf.64.1775741222260; Thu, 09 Apr 2026 06:27:02 -0700 (PDT) Date: Thu, 09 Apr 2026 06:27:02 -0700 In-Reply-To: X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69d7a926.a00a0220.468cb.001a.GAE@google.com> Subject: Re: [syzbot] [cgroups?] KASAN: slab-use-after-free Read in pressure_write From: syzbot To: eadavis@qq.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_remove ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.2.19/6647 is trying to acquire lock: ffff8880573dce18 (kn->active#59){++++}-{0:0}, at: __kernfs_remove+0x3cf/0x660 fs/kernfs/dir.c:1513 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: -> #3 (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:4313 kernfs_fop_write_iter+0x3b0/0x540 fs/kernfs/file.c:352 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 -> #2 (&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 cgroup_file_release+0xe5/0x110 kernel/cgroup/cgroup.c:4284 kernfs_release_file fs/kernfs/file.c:764 [inline] kernfs_fop_release+0x21d/0x450 fs/kernfs/file.c:779 __fput+0x461/0xa90 fs/file_table.c:469 fput_close_sync+0x11f/0x240 fs/file_table.c:574 __do_sys_close fs/open.c:1509 [inline] __se_sys_close fs/open.c:1494 [inline] __x64_sys_close+0x7e/0x110 fs/open.c:1494 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 (&kernfs_locks->open_file_mutex[count]){+.+.}-{4:4}: __mutex_lock_common kernel/locking/rtmutex_api.c:533 [inline] mutex_lock_nested+0x5a/0x1d0 kernel/locking/rtmutex_api.c:552 kernfs_open_file_mutex_lock fs/kernfs/file.c:56 [inline] kernfs_get_open_node fs/kernfs/file.c:538 [inline] kernfs_fop_open+0x6e6/0xcb0 fs/kernfs/file.c:718 do_dentry_open+0x83d/0x13e0 fs/open.c:949 vfs_open+0x3b/0x350 fs/open.c:1081 do_open fs/namei.c:4677 [inline] path_openat+0x2e43/0x38a0 fs/namei.c:4836 do_file_open+0x23e/0x4a0 fs/namei.c:4865 do_sys_openat2+0x113/0x200 fs/open.c:1366 do_sys_open fs/open.c:1372 [inline] __do_sys_openat fs/open.c:1388 [inline] __se_sys_openat fs/open.c:1383 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1383 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 (kn->active#59){++++}-{0:0}: 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 kernfs_drain+0x284/0x600 fs/kernfs/dir.c:511 __kernfs_remove+0x3cf/0x660 fs/kernfs/dir.c:1513 kernfs_remove_by_name_ns+0xaf/0x130 fs/kernfs/dir.c:1722 kernfs_remove_by_name include/linux/kernfs.h:633 [inline] cgroup_rm_file kernel/cgroup/cgroup.c:1758 [inline] cgroup_addrm_files+0x684/0xc30 kernel/cgroup/cgroup.c:4485 cgroup_destroy_locked+0x321/0x630 kernel/cgroup/cgroup.c:6199 cgroup_rmdir+0x3e8/0x710 kernel/cgroup/cgroup.c:6313 kernfs_iop_rmdir+0x203/0x350 fs/kernfs/dir.c:1291 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: kn->active#59 --> &of->mutex --> cgroup_mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(cgroup_mutex); lock(&of->mutex); lock(cgroup_mutex); lock(kn->active#59); *** DEADLOCK *** 4 locks held by syz.2.19/6647: #0: ffff88803b86e480 (sb_writers#9){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:493 #1: ffff8880441e1778 (&type->i_mutex_dir_key#6/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:1073 [inline] #1: ffff8880441e1778 (&type->i_mutex_dir_key#6/1){+.+.}-{4:4}, at: __start_dirop fs/namei.c:2929 [inline] #1: ffff8880441e1778 (&type->i_mutex_dir_key#6/1){+.+.}-{4:4}, at: start_dirop fs/namei.c:2940 [inline] #1: ffff8880441e1778 (&type->i_mutex_dir_key#6/1){+.+.}-{4:4}, at: filename_rmdir+0x1cd/0x520 fs/namei.c:5392 #2: ffff88804b42c8f8 (&type->i_mutex_dir_key#6){++++}-{4:4}, at: inode_lock include/linux/fs.h:1028 [inline] #2: ffff88804b42c8f8 (&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: 6647 Comm: syz.2.19 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 kernfs_drain+0x284/0x600 fs/kernfs/dir.c:511 __kernfs_remove+0x3cf/0x660 fs/kernfs/dir.c:1513 kernfs_remove_by_name_ns+0xaf/0x130 fs/kernfs/dir.c:1722 kernfs_remove_by_name include/linux/kernfs.h:633 [inline] cgroup_rm_file kernel/cgroup/cgroup.c:1758 [inline] cgroup_addrm_files+0x684/0xc30 kernel/cgroup/cgroup.c:4485 cgroup_destroy_locked+0x321/0x630 kernel/cgroup/cgroup.c:6199 cgroup_rmdir+0x3e8/0x710 kernel/cgroup/cgroup.c:6313 kernfs_iop_rmdir+0x203/0x350 fs/kernfs/dir.c:1291 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: 0033:0x7f38b3fcc819 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:00007f38b362e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000054 RAX: ffffffffffffffda RBX: 00007f38b4245fa0 RCX: 00007f38b3fcc819 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000100 RBP: 00007f38b4062c91 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 00007f38b4246038 R14: 00007f38b4245fa0 R15: 00007ffef200b028 Tested on: commit: 7f87a5ea Merge tag 'hid-for-linus-2026040801' of git:/.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=16bd8cd2580000 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=12ddbbd6580000