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AJvYcCUQyJMP9bh7AqNNIIoUHAB6gz8vaByve+xoevIeSCpvKMNKFfQDnbbLJel5UM4uvGu8SeVVdxLRmMVeGyXp5p/U5oeVFmydCecotwWf X-Gm-Message-State: AOJu0Yy0RIA8Wlm2G/Dlyd9HxTLyLO4V6phqv1EjfhKf4SuYDZ7h6aSv dYVpO+GFCmZHaiXwe2QjUqWw899dSxw48yixnGYP3wgx+/kPWzWTwxLjFyxppK5BU2ojTUaUQ/3 Ota9dRG+ucIBVpgzwBDN7IbY/0X+psk/yE2BvWzB32lbR08mHMd3TPZg= X-Google-Smtp-Source: AGHT+IEB9c/4MTmwA/MkyZOIVo07Psc1I9x7T/CZ8GxIwruKXlg685n/W7Dw7rC/na6w2Jk6UAwJJL3Ok6F1uOdn9t+L12Wo2yTi Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6638:148b:b0:47f:1cf3:e571 with SMTP id j11-20020a056638148b00b0047f1cf3e571mr31145jak.3.1712192882235; Wed, 03 Apr 2024 18:08:02 -0700 (PDT) Date: Wed, 03 Apr 2024 18:08:02 -0700 In-Reply-To: <20240404004257.3933-1-hdanton@sina.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <0000000000008885bc06153af8ef@google.com> Subject: Re: [syzbot] [kernfs?] possible deadlock in kernfs_fop_llseek 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_fop_llseek ====================================================== WARNING: possible circular locking dependency detected 6.8.0-syzkaller-08951-gfe46a7dd189e-dirty #0 Not tainted ------------------------------------------------------ syz-executor.0/5486 is trying to acquire lock: ffff88807ec0b888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_llseek+0x7e/0x2a0 fs/kernfs/file.c:867 but task is already holding lock: ffff888050982238 (&ovl_i_lock_key[depth]){+.+.}-{3:3}, at: ovl_inode_lock fs/overlayfs/overlayfs.h:649 [inline] ffff888050982238 (&ovl_i_lock_key[depth]){+.+.}-{3:3}, at: ovl_llseek+0x28a/0x4a0 fs/overlayfs/file.c:215 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&ovl_i_lock_key[depth]){+.+.}-{3:3}: lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754 __mutex_lock_common kernel/locking/mutex.c:608 [inline] __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752 ovl_inode_lock_interruptible fs/overlayfs/overlayfs.h:654 [inline] ovl_nlink_start+0xdc/0x390 fs/overlayfs/util.c:1162 ovl_do_remove+0x1fa/0xd90 fs/overlayfs/dir.c:893 vfs_rmdir+0x367/0x4c0 fs/namei.c:4209 do_rmdir+0x3b5/0x580 fs/namei.c:4268 __do_sys_rmdir fs/namei.c:4287 [inline] __se_sys_rmdir fs/namei.c:4285 [inline] __x64_sys_rmdir+0x49/0x60 fs/namei.c:4285 do_syscall_64+0xfb/0x240 entry_SYSCALL_64_after_hwframe+0x6d/0x75 -> #1 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}: lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754 down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526 inode_lock_shared include/linux/fs.h:803 [inline] lookup_slow+0x45/0x70 fs/namei.c:1708 walk_component+0x2e1/0x410 fs/namei.c:2004 lookup_last fs/namei.c:2461 [inline] path_lookupat+0x16f/0x450 fs/namei.c:2485 filename_lookup+0x256/0x610 fs/namei.c:2514 kern_path+0x35/0x50 fs/namei.c:2622 lookup_bdev+0xc5/0x290 block/bdev.c:1072 resume_store+0x1a0/0x710 kernel/power/hibernate.c:1235 kernfs_fop_write_iter+0x3a4/0x500 fs/kernfs/file.c:334 call_write_iter include/linux/fs.h:2108 [inline] new_sync_write fs/read_write.c:497 [inline] vfs_write+0xa84/0xcb0 fs/read_write.c:590 ksys_write+0x1a0/0x2c0 fs/read_write.c:643 do_syscall_64+0xfb/0x240 entry_SYSCALL_64_after_hwframe+0x6d/0x75 -> #0 (&of->mutex){+.+.}-{3:3}: check_prev_add kernel/locking/lockdep.c:3134 [inline] check_prevs_add kernel/locking/lockdep.c:3253 [inline] validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137 lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754 __mutex_lock_common kernel/locking/mutex.c:608 [inline] __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752 kernfs_fop_llseek+0x7e/0x2a0 fs/kernfs/file.c:867 ovl_llseek+0x335/0x4a0 fs/overlayfs/file.c:219 vfs_llseek fs/read_write.c:289 [inline] ksys_lseek fs/read_write.c:302 [inline] __do_sys_lseek fs/read_write.c:313 [inline] __se_sys_lseek fs/read_write.c:311 [inline] __x64_sys_lseek+0x153/0x1e0 fs/read_write.c:311 do_syscall_64+0xfb/0x240 entry_SYSCALL_64_after_hwframe+0x6d/0x75 other info that might help us debug this: Chain exists of: &of->mutex --> &ovl_i_mutex_dir_key[depth] --> &ovl_i_lock_key[depth] Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&ovl_i_lock_key[depth]); lock(&ovl_i_mutex_dir_key[depth]); lock(&ovl_i_lock_key[depth]); lock(&of->mutex); *** DEADLOCK *** 3 locks held by syz-executor.0/5486: #0: ffff8880707c8ac8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x259/0x320 fs/file.c:1191 #1: ffff888050981e80 (&ovl_i_mutex_key[depth]){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:793 [inline] #1: ffff888050981e80 (&ovl_i_mutex_key[depth]){+.+.}-{3:3}, at: ovl_llseek+0x277/0x4a0 fs/overlayfs/file.c:207 #2: ffff888050982238 (&ovl_i_lock_key[depth]){+.+.}-{3:3}, at: ovl_inode_lock fs/overlayfs/overlayfs.h:649 [inline] #2: ffff888050982238 (&ovl_i_lock_key[depth]){+.+.}-{3:3}, at: ovl_llseek+0x28a/0x4a0 fs/overlayfs/file.c:215 stack backtrace: CPU: 0 PID: 5486 Comm: syz-executor.0 Not tainted 6.8.0-syzkaller-08951-gfe46a7dd189e-dirty #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024 Call Trace: __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114 check_noncircular+0x36a/0x4a0 kernel/locking/lockdep.c:2187 check_prev_add kernel/locking/lockdep.c:3134 [inline] check_prevs_add kernel/locking/lockdep.c:3253 [inline] validate_chain+0x18cb/0x58e0 kernel/locking/lockdep.c:3869 __lock_acquire+0x1346/0x1fd0 kernel/locking/lockdep.c:5137 lock_acquire+0x1e4/0x530 kernel/locking/lockdep.c:5754 __mutex_lock_common kernel/locking/mutex.c:608 [inline] __mutex_lock+0x136/0xd70 kernel/locking/mutex.c:752 kernfs_fop_llseek+0x7e/0x2a0 fs/kernfs/file.c:867 ovl_llseek+0x335/0x4a0 fs/overlayfs/file.c:219 vfs_llseek fs/read_write.c:289 [inline] ksys_lseek fs/read_write.c:302 [inline] __do_sys_lseek fs/read_write.c:313 [inline] __se_sys_lseek fs/read_write.c:311 [inline] __x64_sys_lseek+0x153/0x1e0 fs/read_write.c:311 do_syscall_64+0xfb/0x240 entry_SYSCALL_64_after_hwframe+0x6d/0x75 RIP: 0033:0x7fe1f567dde9 Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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 b0 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007fe1f64370c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000008 RAX: ffffffffffffffda RBX: 00007fe1f57abf80 RCX: 00007fe1f567dde9 RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000005 RBP: 00007fe1f56ca47a R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 000000000000000b R14: 00007fe1f57abf80 R15: 00007ffe353f4cc8 Tested on: commit: fe46a7dd Merge tag 'sound-6.9-rc1' of git://git.kernel.. git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git console output: https://syzkaller.appspot.com/x/log.txt?x=104e8475180000 kernel config: https://syzkaller.appspot.com/x/.config?x=4d90a36f0cab495a dashboard link: https://syzkaller.appspot.com/bug?extid=9a5b0ced8b1bfb238b56 compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40 patch: https://syzkaller.appspot.com/x/patch.diff?x=1799f6ad180000