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charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 253c82b3a2ce Add linux-next specific files for 20250217 git tree: linux-next console+strace: https://syzkaller.appspot.com/x/log.txt?x=15141898580000 kernel config: https://syzkaller.appspot.com/x/.config?x=f984ff1d92cb4017 dashboard link: https://syzkaller.appspot.com/bug?extid=ecccecbc636b455f9084 compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=175b7da4580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=17141898580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/af8b0f79abb4/disk-253c82b3.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/463f7d416e09/vmlinux-253c82b3.xz kernel image: https://storage.googleapis.com/syzbot-assets/07101e97dd04/bzImage-253c82b3.xz The issue was bisected to: commit 5b2fabf7fe8f745ff214ff003e6067b64f172271 Author: Sebastian Andrzej Siewior Date: Thu Feb 13 14:50:20 2025 +0000 kernfs: Acquire kernfs_rwsem in kernfs_node_dentry(). bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=15a9fda4580000 final oops: https://syzkaller.appspot.com/x/report.txt?x=17a9fda4580000 console output: https://syzkaller.appspot.com/x/log.txt?x=13a9fda4580000 IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+ecccecbc636b455f9084@syzkaller.appspotmail.com Fixes: 5b2fabf7fe8f ("kernfs: Acquire kernfs_rwsem in kernfs_node_dentry().") ============================= WARNING: suspicious RCU usage 6.14.0-rc2-next-20250217-syzkaller #0 Not tainted ----------------------------- fs/kernfs/mount.c:243 suspicious rcu_dereference_check() usage! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 3 locks held by syz-executor215/5837: #0: ffff88802ab0b870 (&fc->uapi_mutex){+.+.}-{4:4}, at: __do_sys_fsconfig fs/fsopen.c:465 [inline] #0: ffff88802ab0b870 (&fc->uapi_mutex){+.+.}-{4:4}, at: __se_sys_fsconfig+0x9b2/0xf60 fs/fsopen.c:344 #1: ffff8880355560e0 (&type->s_umount_key#46){+.+.}-{4:4}, at: __super_lock fs/super.c:56 [inline] #1: ffff8880355560e0 (&type->s_umount_key#46){+.+.}-{4:4}, at: super_lock+0x196/0x400 fs/super.c:120 #2: ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:241 [inline] #2: ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_node_dentry+0xc3/0x2d0 fs/kernfs/mount.c:223 stack backtrace: CPU: 0 UID: 0 PID: 5837 Comm: syz-executor215 Not tainted 6.14.0-rc2-next-20250217-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 lockdep_rcu_suspicious+0x226/0x340 kernel/locking/lockdep.c:6847 kernfs_node_dentry+0x24b/0x2d0 fs/kernfs/mount.c:243 cgroup_do_get_tree+0x248/0x390 kernel/cgroup/cgroup.c:2233 cgroup_get_tree+0xbb/0x230 kernel/cgroup/cgroup.c:2272 vfs_get_tree+0x90/0x2b0 fs/super.c:1759 vfs_cmd_create+0xa0/0x1f0 fs/fsopen.c:225 __do_sys_fsconfig fs/fsopen.c:467 [inline] __se_sys_fsconfig+0xa33/0xf60 fs/fsopen.c:344 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f09e41a2de9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 18 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffe4f61eba8 EFLAGS: 00000246 ORIG_RAX: 00000000000001af RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f09e41a2de9 RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f09e41ec036 R13: 00007ffe4f61ebe0 R14: 00007ffe4f61ec20 R15: 0000000000000000 ============================================ WARNING: possible recursive locking detected 6.14.0-rc2-next-20250217-syzkaller #0 Not tainted -------------------------------------------- syz-executor215/5837 is trying to acquire lock: ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_dop_revalidate+0xa2/0x5d0 fs/kernfs/dir.c:1178 but task is already holding lock: ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:241 [inline] ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_node_dentry+0xc3/0x2d0 fs/kernfs/mount.c:223 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(&root->kernfs_rwsem); lock(&root->kernfs_rwsem); *** DEADLOCK *** May be due to missing lock nesting notation 3 locks held by syz-executor215/5837: #0: ffff88802ab0b870 (&fc->uapi_mutex){+.+.}-{4:4}, at: __do_sys_fsconfig fs/fsopen.c:465 [inline] #0: ffff88802ab0b870 (&fc->uapi_mutex){+.+.}-{4:4}, at: __se_sys_fsconfig+0x9b2/0xf60 fs/fsopen.c:344 #1: ffff8880355560e0 (&type->s_umount_key#46){+.+.}-{4:4}, at: __super_lock fs/super.c:56 [inline] #1: ffff8880355560e0 (&type->s_umount_key#46){+.+.}-{4:4}, at: super_lock+0x196/0x400 fs/super.c:120 #2: ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: class_rwsem_read_constructor include/linux/rwsem.h:241 [inline] #2: ffff88801bef7148 (&root->kernfs_rwsem){++++}-{4:4}, at: kernfs_node_dentry+0xc3/0x2d0 fs/kernfs/mount.c:223 stack backtrace: CPU: 1 UID: 0 PID: 5837 Comm: syz-executor215 Not tainted 6.14.0-rc2-next-20250217-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 print_deadlock_bug+0x483/0x620 kernel/locking/lockdep.c:3039 check_deadlock kernel/locking/lockdep.c:3091 [inline] validate_chain+0x15e2/0x5920 kernel/locking/lockdep.c:3893 __lock_acquire+0x1397/0x2100 kernel/locking/lockdep.c:5228 lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5851 down_read+0xb1/0xa40 kernel/locking/rwsem.c:1524 kernfs_dop_revalidate+0xa2/0x5d0 fs/kernfs/dir.c:1178 d_revalidate fs/namei.c:923 [inline] lookup_dcache fs/namei.c:1651 [inline] lookup_one_unlocked+0x23b/0x2d0 fs/namei.c:2972 lookup_one_positive_unlocked fs/namei.c:3003 [inline] lookup_positive_unlocked+0x2b/0xb0 fs/namei.c:3043 kernfs_node_dentry+0x139/0x2d0 fs/kernfs/mount.c:244 cgroup_do_get_tree+0x248/0x390 kernel/cgroup/cgroup.c:2233 cgroup_get_tree+0xbb/0x230 kernel/cgroup/cgroup.c:2272 vfs_get_tree+0x90/0x2b0 fs/super.c:1759 vfs_cmd_create+0xa0/0x1f0 fs/fsopen.c:225 __do_sys_fsconfig fs/fsopen.c:467 [inline] __se_sys_fsconfig+0xa33/0xf60 fs/fsopen.c:344 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f09e41a2de9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 61 18 00 00 90 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 b8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffe4f61eba8 EFLAGS: 00000246 ORIG_RAX: 00000000000001af RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f09e41a2de9 RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000000000003 RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f09e41ec036 R13: 00007ffe4f61ebe0 R14: 00007ffe4f61ec20 R15: 0000000000000000 --- 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. For information about bisection process see: https://goo.gl/tpsmEJ#bisection If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want syzbot to run the reproducer, reply with: #syz test: git://repo/address.git branch-or-commit-hash If you attach or paste a git patch, syzbot will apply it before testing. 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