linux-kernel - Re: [syzbot] [jfs?] [bcachefs?] KASAN: null-ptr-deref Read in drop

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Message-ID: <68022717.050a0220.243d89.001a.GAE@google.com>
Date: Fri, 18 Apr 2025 03:19:03 -0700
From: syzbot <syzbot+de1498ff3a934ac5e8b4@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, richard120310@...il.com, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [jfs?] [bcachefs?] KASAN: null-ptr-deref Read in
 drop_buffers (3)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
kernel BUG in z3fold_page_migrate

 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xabe/0x18e0 kernel/workqueue.c:3319
 worker_thread+0x870/0xd30 kernel/workqueue.c:3400
 kthread+0x7a9/0x920 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
------------[ cut here ]------------
kernel BUG at mm/z3fold.c:1293!
Oops: invalid opcode: 0000 [#1] PREEMPT SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 30 Comm: kcompactd1 Not tainted 6.14.0-rc6-syzkaller-00253-gcb82ca153949-dirty #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:z3fold_page_migrate+0xc22/0x1170 mm/z3fold.c:1293
Code: ff 48 89 ef 48 c7 c6 a0 3e 38 8c e8 f8 1a d8 ff 90 0f 0b e8 60 85 8d ff 48 8b 7c 24 10 48 c7 c6 00 3f 38 8c e8 df 1a d8 ff 90 <0f> 0b 48 85 db 0f 85 83 00 00 00 0f 1f 44 00 00 e8 39 85 8d ff e9
RSP: 0018:ffffc90000516eb8 EFLAGS: 00010246
RAX: 760a2d6b4e715d00 RBX: 0000000000000000 RCX: 0000000000000001
RDX: dffffc0000000000 RSI: ffffffff8c2ab220 RDI: 0000000000000001
RBP: ffffea00014d6180 R08: ffffffff903cfd77 R09: 1ffffffff2079fae
R10: dffffc0000000000 R11: fffffbfff2079faf R12: dffffc0000000000
R13: ffffffff8c383d08 R14: 04fff00000010001 R15: 1ffffd400029ac30
FS:  0000000000000000(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c00018b600 CR3: 0000000053580000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 move_to_new_folio+0x9a5/0xc20 mm/migrate.c:1071
 migrate_folio_move mm/migrate.c:1360 [inline]
 migrate_folios_move mm/migrate.c:1712 [inline]
 migrate_pages_batch+0x1e84/0x30b0 mm/migrate.c:1959
 migrate_pages_sync mm/migrate.c:2016 [inline]
 migrate_pages+0x2701/0x3680 mm/migrate.c:2098
 compact_zone+0x33d5/0x4ae0 mm/compaction.c:2663
 kcompactd_do_work mm/compaction.c:3111 [inline]
 kcompactd+0x9a5/0x1540 mm/compaction.c:3205
 kthread+0x7a9/0x920 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:z3fold_page_migrate+0xc22/0x1170 mm/z3fold.c:1293
Code: ff 48 89 ef 48 c7 c6 a0 3e 38 8c e8 f8 1a d8 ff 90 0f 0b e8 60 85 8d ff 48 8b 7c 24 10 48 c7 c6 00 3f 38 8c e8 df 1a d8 ff 90 <0f> 0b 48 85 db 0f 85 83 00 00 00 0f 1f 44 00 00 e8 39 85 8d ff e9
RSP: 0018:ffffc90000516eb8 EFLAGS: 00010246
RAX: 760a2d6b4e715d00 RBX: 0000000000000000 RCX: 0000000000000001
RDX: dffffc0000000000 RSI: ffffffff8c2ab220 RDI: 0000000000000001
RBP: ffffea00014d6180 R08: ffffffff903cfd77 R09: 1ffffffff2079fae
R10: dffffc0000000000 R11: fffffbfff2079faf R12: dffffc0000000000
R13: ffffffff8c383d08 R14: 04fff00000010001 R15: 1ffffd400029ac30
FS:  0000000000000000(0000) GS:ffff88801fc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd22cd0bfd8 CR3: 00000000534f0000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


Tested on:

commit:         cb82ca15 Merge tag 'usb-6.14-rc7' of git://git.kernel...
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=108a24cc580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=522f1f3e5f61442b
dashboard link: https://syzkaller.appspot.com/bug?extid=de1498ff3a934ac5e8b4
compiler:       Debian clang version 15.0.6, Debian LLD 15.0.6
patch:          https://syzkaller.appspot.com/x/patch.diff?x=17949fe4580000