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List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:6607:b0:659:9a49:8e2c with SMTP id 006d021491bc7-6599a49c3d7mr682160eaf.30.1765003765128; Fri, 05 Dec 2025 22:49:25 -0800 (PST) Date: Fri, 05 Dec 2025 22:49:25 -0800 In-Reply-To: <68c8fd75.050a0220.2ff435.03bd.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6933d1f5.a70a0220.38f243.0016.GAE@google.com> Subject: Re: [syzbot] [ext4?] possible deadlock in do_writepages (2) From: syzbot To: akpm@linux-foundation.org, linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com, willy@infradead.org Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: d1d36025a617 Merge tag 'probes-v6.19' of git://git.kernel... git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=17c5821a580000 kernel config: https://syzkaller.appspot.com/x/.config?x=96b1065fc3079f82 dashboard link: https://syzkaller.appspot.com/bug?extid=756f498a88797cda9299 compiler: gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10133c1a580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16178992580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/01358f3e734d/disk-d1d36025.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/8c72ac5de2c8/vmlinux-d1d36025.xz kernel image: https://storage.googleapis.com/syzbot-assets/44b0ffcb520c/bzImage-d1d36025.xz mounted in repro: https://storage.googleapis.com/syzbot-assets/8c26f8a66fe2/mount_0.gz fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=12bc02c2580000) IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+756f498a88797cda9299@syzkaller.appspotmail.com loop0: detected capacity change from 0 to 512 ====================================================== WARNING: possible circular locking dependency detected syzkaller #0 Not tainted ------------------------------------------------------ syz.0.17/6041 is trying to acquire lock: ffff88803394eb98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: do_writepages+0x27a/0x600 mm/page-writeback.c:2598 but task is already holding lock: ffff888059c16aa8 (&ei->xattr_sem){++++}-{4:4}, at: ext4_write_trylock_xattr fs/ext4/xattr.h:164 [inline] ffff888059c16aa8 (&ei->xattr_sem){++++}-{4:4}, at: ext4_try_to_expand_extra_isize fs/ext4/inode.c:6389 [inline] ffff888059c16aa8 (&ei->xattr_sem){++++}-{4:4}, at: __ext4_mark_inode_dirty+0x4ba/0x840 fs/ext4/inode.c:6470 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&ei->xattr_sem){++++}-{4:4}: down_read+0x9b/0x460 kernel/locking/rwsem.c:1537 ext4_setattr+0x869/0x28d0 fs/ext4/inode.c:5865 notify_change+0x6d2/0x1290 fs/attr.c:546 chown_common+0x549/0x680 fs/open.c:788 do_fchownat+0x1a7/0x200 fs/open.c:819 __do_sys_chown fs/open.c:839 [inline] __se_sys_chown fs/open.c:837 [inline] __x64_sys_chown+0x7b/0xc0 fs/open.c:837 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f -> #1 (jbd2_handle){++++}-{0:0}: wait_transaction_locked+0x191/0x230 fs/jbd2/transaction.c:151 add_transaction_credits+0x110/0xe60 fs/jbd2/transaction.c:222 start_this_handle+0x3e7/0x1410 fs/jbd2/transaction.c:403 jbd2__journal_start+0x394/0x6a0 fs/jbd2/transaction.c:501 __ext4_journal_start_sb+0x195/0x640 fs/ext4/ext4_jbd2.c:114 __ext4_journal_start fs/ext4/ext4_jbd2.h:242 [inline] ext4_do_writepages+0xc23/0x3c70 fs/ext4/inode.c:2914 ext4_writepages+0x37a/0x7d0 fs/ext4/inode.c:3026 do_writepages+0x27a/0x600 mm/page-writeback.c:2598 __writeback_single_inode+0x168/0x14a0 fs/fs-writeback.c:1737 writeback_sb_inodes+0x795/0x1de0 fs/fs-writeback.c:2030 __writeback_inodes_wb+0xf8/0x2d0 fs/fs-writeback.c:2107 wb_writeback+0x799/0xae0 fs/fs-writeback.c:2218 wb_check_old_data_flush fs/fs-writeback.c:2322 [inline] wb_do_writeback fs/fs-writeback.c:2375 [inline] wb_workfn+0x8a0/0xbb0 fs/fs-writeback.c:2403 process_one_work+0x9ba/0x1b20 kernel/workqueue.c:3257 process_scheduled_works kernel/workqueue.c:3340 [inline] worker_thread+0x6c8/0xf10 kernel/workqueue.c:3421 kthread+0x3c5/0x780 kernel/kthread.c:463 ret_from_fork+0x983/0xb10 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 -> #0 (&sbi->s_writepages_rwsem){++++}-{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+0x1542/0x22f0 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x330 kernel/locking/lockdep.c:5825 percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline] percpu_down_read include/linux/percpu-rwsem.h:77 [inline] ext4_writepages_down_read fs/ext4/ext4.h:1820 [inline] ext4_writepages+0x224/0x7d0 fs/ext4/inode.c:3025 do_writepages+0x27a/0x600 mm/page-writeback.c:2598 __writeback_single_inode+0x168/0x14a0 fs/fs-writeback.c:1737 writeback_single_inode+0x5ea/0x11f0 fs/fs-writeback.c:1858 write_inode_now+0x170/0x1e0 fs/fs-writeback.c:2924 iput_final fs/inode.c:1941 [inline] iput.part.0+0x815/0x1190 fs/inode.c:2003 iput+0x35/0x40 fs/inode.c:1966 ext4_xattr_block_set+0x67c/0x3640 fs/ext4/xattr.c:2203 ext4_xattr_move_to_block fs/ext4/xattr.c:2668 [inline] ext4_xattr_make_inode_space fs/ext4/xattr.c:2743 [inline] ext4_expand_extra_isize_ea+0x1442/0x1ab0 fs/ext4/xattr.c:2831 __ext4_expand_extra_isize+0x346/0x480 fs/ext4/inode.c:6349 ext4_try_to_expand_extra_isize fs/ext4/inode.c:6392 [inline] __ext4_mark_inode_dirty+0x544/0x840 fs/ext4/inode.c:6470 ext4_evict_inode+0x713/0x1730 fs/ext4/inode.c:253 evict+0x3c2/0xad0 fs/inode.c:837 iput_final fs/inode.c:1951 [inline] iput.part.0+0x621/0x1190 fs/inode.c:2003 iput+0x35/0x40 fs/inode.c:1966 ext4_orphan_cleanup+0x731/0x11e0 fs/ext4/orphan.c:472 __ext4_fill_super fs/ext4/super.c:5658 [inline] ext4_fill_super+0x7ec1/0xb570 fs/ext4/super.c:5777 get_tree_bdev_flags+0x38c/0x620 fs/super.c:1699 vfs_get_tree+0x8e/0x330 fs/super.c:1759 fc_mount fs/namespace.c:1199 [inline] do_new_mount_fc fs/namespace.c:3636 [inline] do_new_mount fs/namespace.c:3712 [inline] path_mount+0x7bf/0x23a0 fs/namespace.c:4022 do_mount fs/namespace.c:4035 [inline] __do_sys_mount fs/namespace.c:4224 [inline] __se_sys_mount fs/namespace.c:4201 [inline] __x64_sys_mount+0x293/0x310 fs/namespace.c:4201 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/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: &sbi->s_writepages_rwsem --> jbd2_handle --> &ei->xattr_sem Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&ei->xattr_sem); lock(jbd2_handle); lock(&ei->xattr_sem); rlock(&sbi->s_writepages_rwsem); *** DEADLOCK *** 3 locks held by syz.0.17/6041: #0: ffff88803394c0e0 (&type->s_umount_key#27/1){+.+.}-{4:4}, at: alloc_super+0x244/0xd00 fs/super.c:344 #1: ffff88803394c610 (sb_internal){.+.+}-{0:0}, at: evict+0x3c2/0xad0 fs/inode.c:837 #2: ffff888059c16aa8 (&ei->xattr_sem){++++}-{4:4}, at: ext4_write_trylock_xattr fs/ext4/xattr.h:164 [inline] #2: ffff888059c16aa8 (&ei->xattr_sem){++++}-{4:4}, at: ext4_try_to_expand_extra_isize fs/ext4/inode.c:6389 [inline] #2: ffff888059c16aa8 (&ei->xattr_sem){++++}-{4:4}, at: __ext4_mark_inode_dirty+0x4ba/0x840 fs/ext4/inode.c:6470 stack backtrace: CPU: 1 UID: 0 PID: 6041 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120 print_circular_bug+0x2db/0x410 kernel/locking/lockdep.c:2043 check_noncircular+0x146/0x160 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+0x1542/0x22f0 kernel/locking/lockdep.c:5237 lock_acquire kernel/locking/lockdep.c:5868 [inline] lock_acquire+0x179/0x330 kernel/locking/lockdep.c:5825 percpu_down_read_internal include/linux/percpu-rwsem.h:53 [inline] percpu_down_read include/linux/percpu-rwsem.h:77 [inline] ext4_writepages_down_read fs/ext4/ext4.h:1820 [inline] ext4_writepages+0x224/0x7d0 fs/ext4/inode.c:3025 do_writepages+0x27a/0x600 mm/page-writeback.c:2598 __writeback_single_inode+0x168/0x14a0 fs/fs-writeback.c:1737 writeback_single_inode+0x5ea/0x11f0 fs/fs-writeback.c:1858 write_inode_now+0x170/0x1e0 fs/fs-writeback.c:2924 iput_final fs/inode.c:1941 [inline] iput.part.0+0x815/0x1190 fs/inode.c:2003 iput+0x35/0x40 fs/inode.c:1966 ext4_xattr_block_set+0x67c/0x3640 fs/ext4/xattr.c:2203 ext4_xattr_move_to_block fs/ext4/xattr.c:2668 [inline] ext4_xattr_make_inode_space fs/ext4/xattr.c:2743 [inline] ext4_expand_extra_isize_ea+0x1442/0x1ab0 fs/ext4/xattr.c:2831 __ext4_expand_extra_isize+0x346/0x480 fs/ext4/inode.c:6349 ext4_try_to_expand_extra_isize fs/ext4/inode.c:6392 [inline] __ext4_mark_inode_dirty+0x544/0x840 fs/ext4/inode.c:6470 ext4_evict_inode+0x713/0x1730 fs/ext4/inode.c:253 evict+0x3c2/0xad0 fs/inode.c:837 iput_final fs/inode.c:1951 [inline] iput.part.0+0x621/0x1190 fs/inode.c:2003 iput+0x35/0x40 fs/inode.c:1966 ext4_orphan_cleanup+0x731/0x11e0 fs/ext4/orphan.c:472 __ext4_fill_super fs/ext4/super.c:5658 [inline] ext4_fill_super+0x7ec1/0xb570 fs/ext4/super.c:5777 get_tree_bdev_flags+0x38c/0x620 fs/super.c:1699 vfs_get_tree+0x8e/0x330 fs/super.c:1759 fc_mount fs/namespace.c:1199 [inline] do_new_mount_fc fs/namespace.c:3636 [inline] do_new_mount fs/namespace.c:3712 [inline] path_mount+0x7bf/0x23a0 fs/namespace.c:4022 do_mount fs/namespace.c:4035 [inline] __do_sys_mount fs/namespace.c:4224 [inline] __se_sys_mount fs/namespace.c:4201 [inline] __x64_sys_mount+0x293/0x310 fs/namespace.c:4201 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f24b8790eea Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffe9c113938 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 00007ffe9c1139c0 RCX: 00007f24b8790eea RDX: 0000200000000180 RSI: 00002000000001c0 RDI: 00007ffe9c113980 RBP: 0000200000000180 R08: 00007ffe9c1139c0 R09: 0000000000800700 R10: 0000000000800700 R11: 0000000000000246 R12: 00002000000001c0 R13: 00007ffe9c113980 R14: 000000000000046f R15: 000000000000002c ------------[ cut here ]------------ EA inode 11 i_nlink=2 WARNING: fs/ext4/xattr.c:1056 at 0x0, CPU#0: syz.0.17/6041 Modules linked in: CPU: 0 UID: 0 PID: 6041 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025 RIP: 0010:ext4_xattr_inode_update_ref+0x4be/0x5b0 fs/ext4/xattr.c:1056 Code: 40 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00 0f 85 f1 00 00 00 48 8d 3d 09 d6 fb 0d 48 8b 73 40 44 89 e2 <67> 48 0f b9 3a e9 06 ff ff ff e8 23 c7 2c ff 48 8d 7b 40 48 b8 00 RSP: 0018:ffffc900033c7178 EFLAGS: 00010246 RAX: dffffc0000000000 RBX: ffff888059d59f78 RCX: ffffffff82915db4 RDX: 0000000000000002 RSI: 000000000000000b RDI: ffffffff908d34b0 RBP: ffffc900033c7240 R08: 0000000000000005 R09: 0000000000000001 R10: 0000000000000002 R11: 0000000000000001 R12: 0000000000000002 R13: ffffffffffffffff R14: 1ffff92000678e32 R15: ffff888059d5a168 FS: 00005555694d6500(0000) GS:ffff88812495e000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00005641e7f0f078 CR3: 00000000744a9000 CR4: 0000000000350ef0 Call Trace: ext4_xattr_inode_dec_ref fs/ext4/xattr.c:1081 [inline] ext4_xattr_set_entry+0x158f/0x1f00 fs/ext4/xattr.c:1723 ext4_xattr_ibody_set+0x3d6/0x5d0 fs/ext4/xattr.c:2272 ext4_xattr_move_to_block fs/ext4/xattr.c:2675 [inline] ext4_xattr_make_inode_space fs/ext4/xattr.c:2743 [inline] ext4_expand_extra_isize_ea+0x148c/0x1ab0 fs/ext4/xattr.c:2831 __ext4_expand_extra_isize+0x346/0x480 fs/ext4/inode.c:6349 ext4_try_to_expand_extra_isize fs/ext4/inode.c:6392 [inline] __ext4_mark_inode_dirty+0x544/0x840 fs/ext4/inode.c:6470 ext4_evict_inode+0x713/0x1730 fs/ext4/inode.c:253 evict+0x3c2/0xad0 fs/inode.c:837 iput_final fs/inode.c:1951 [inline] iput.part.0+0x621/0x1190 fs/inode.c:2003 iput+0x35/0x40 fs/inode.c:1966 ext4_orphan_cleanup+0x731/0x11e0 fs/ext4/orphan.c:472 __ext4_fill_super fs/ext4/super.c:5658 [inline] ext4_fill_super+0x7ec1/0xb570 fs/ext4/super.c:5777 get_tree_bdev_flags+0x38c/0x620 fs/super.c:1699 vfs_get_tree+0x8e/0x330 fs/super.c:1759 fc_mount fs/namespace.c:1199 [inline] do_new_mount_fc fs/namespace.c:3636 [inline] do_new_mount fs/namespace.c:3712 [inline] path_mount+0x7bf/0x23a0 fs/namespace.c:4022 do_mount fs/namespace.c:4035 [inline] __do_sys_mount fs/namespace.c:4224 [inline] __se_sys_mount fs/namespace.c:4201 [inline] __x64_sys_mount+0x293/0x310 fs/namespace.c:4201 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcd/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f24b8790eea Code: d8 64 89 02 48 c7 c0 ff ff ff ff eb a6 e8 de 1a 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 49 89 ca b8 a5 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007ffe9c113938 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5 RAX: ffffffffffffffda RBX: 00007ffe9c1139c0 RCX: 00007f24b8790eea RDX: 0000200000000180 RSI: 00002000000001c0 RDI: 00007ffe9c113980 RBP: 0000200000000180 R08: 00007ffe9c1139c0 R09: 0000000000800700 R10: 0000000000800700 R11: 0000000000000246 R12: 00002000000001c0 R13: 00007ffe9c113980 R14: 000000000000046f R15: 000000000000002c ---------------- Code disassembly (best guess): 0: 40 rex 1: 48 b8 00 00 00 00 00 movabs $0xdffffc0000000000,%rax 8: fc ff df b: 48 89 fa mov %rdi,%rdx e: 48 c1 ea 03 shr $0x3,%rdx 12: 80 3c 02 00 cmpb $0x0,(%rdx,%rax,1) 16: 0f 85 f1 00 00 00 jne 0x10d 1c: 48 8d 3d 09 d6 fb 0d lea 0xdfbd609(%rip),%rdi # 0xdfbd62c 23: 48 8b 73 40 mov 0x40(%rbx),%rsi 27: 44 89 e2 mov %r12d,%edx * 2a: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction 2f: e9 06 ff ff ff jmp 0xffffff3a 34: e8 23 c7 2c ff call 0xff2cc75c 39: 48 8d 7b 40 lea 0x40(%rbx),%rdi 3d: 48 rex.W 3e: b8 .byte 0xb8 --- 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.