linux-kernel - Re: [syzbot] [mm?] general protection fault in lru_gen_test

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Message-ID: <6937baa6.a70a0220.38f243.00c4.GAE@google.com>
Date: Mon, 08 Dec 2025 21:59:02 -0800
From: syzbot <syzbot+e008db2ac01e282550ee@...kaller.appspotmail.com>
To: kartikey406@...il.com, linux-kernel@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [mm?] general protection fault in lru_gen_test_recent (2)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
BUG: unable to handle kernel NULL pointer dereference in filemap_read_folio

  shadow=0x11
  Unpacked: memcgid=0 nid=4 eviction=0x0 workingset=0
  NODE_DATA(4)=0000000000000000
*** BUG: INVALID NODE ID 4! ***
CPU: 1 UID: 0 PID: 6408 Comm: syz.0.24 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x16c/0x1f0 lib/dump_stack.c:120
 unpack_shadow+0x1f3/0x270 mm/workingset.c:243
 lru_gen_test_recent+0x9a/0x350 mm/workingset.c:299
 lru_gen_refault mm/workingset.c:329 [inline]
 workingset_refault+0x290/0xd50 mm/workingset.c:585
 filemap_add_folio+0x23d/0x610 mm/filemap.c:981
 do_read_cache_folio+0x23c/0x5c0 mm/filemap.c:4063
 freader_get_folio+0x33a/0x930 lib/buildid.c:58
 freader_fetch+0xbd/0x740 lib/buildid.c:101
 __build_id_parse.isra.0+0xdd/0x6c0 lib/buildid.c:289
 do_procmap_query+0xb0e/0x1080 fs/proc/task_mmu.c:733
 procfs_procmap_ioctl+0x9d/0xe0 fs/proc/task_mmu.c:813
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 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: 0033:0x7fcba4f8f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fcba5ee8038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fcba51e5fa0 RCX: 00007fcba4f8f7c9
RDX: 0000200000000180 RSI: 00000000c0686611 RDI: 0000000000000003
RBP: 00007fcba5013f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcba51e6038 R14: 00007fcba51e5fa0 R15: 00007ffc01f89a28
 </TASK>
WORKINGSET_REFAULT: lru_gen_refault returned
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 32990067 P4D 32990067 PUD 0 
Oops: Oops: 0010 [#1] SMP KASAN NOPTI
CPU: 0 UID: 0 PID: 6408 Comm: syz.0.24 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0018:ffffc90003d1f988 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81f7e52e
RDX: ffff88802e4e4980 RSI: ffffea000167d2c0 RDI: ffff888039482000
RBP: ffffea000167d2c0 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 1ffff920007a3f32
R13: ffff888039482000 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007fcba5ee86c0(0000) GS:ffff8880d6907000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000002bb78000 CR4: 0000000000352ef0
Call Trace:
 <TASK>
 filemap_read_folio+0xc8/0x2a0 mm/filemap.c:2496
 do_read_cache_folio+0x266/0x5c0 mm/filemap.c:4096
 freader_get_folio+0x33a/0x930 lib/buildid.c:58
 freader_fetch+0xbd/0x740 lib/buildid.c:101
 __build_id_parse.isra.0+0xdd/0x6c0 lib/buildid.c:289
 do_procmap_query+0xb0e/0x1080 fs/proc/task_mmu.c:733
 procfs_procmap_ioctl+0x9d/0xe0 fs/proc/task_mmu.c:813
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:597 [inline]
 __se_sys_ioctl fs/ioctl.c:583 [inline]
 __x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:583
 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: 0033:0x7fcba4f8f7c9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fcba5ee8038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fcba51e5fa0 RCX: 00007fcba4f8f7c9
RDX: 0000200000000180 RSI: 00000000c0686611 RDI: 0000000000000003
RBP: 00007fcba5013f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcba51e6038 R14: 00007fcba51e5fa0 R15: 00007ffc01f89a28
 </TASK>
Modules linked in:
CR2: 0000000000000000
---[ end trace 0000000000000000 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0018:ffffc90003d1f988 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81f7e52e
RDX: ffff88802e4e4980 RSI: ffffea000167d2c0 RDI: ffff888039482000
RBP: ffffea000167d2c0 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 1ffff920007a3f32
R13: ffff888039482000 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007fcba5ee86c0(0000) GS:ffff8880d6907000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000002bb78000 CR4: 0000000000352ef0


Tested on:

commit:         cb015814 Merge tag 'f2fs-for-6.19-rc1' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17d01eb4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=dbcb767d1e1208ac
dashboard link: https://syzkaller.appspot.com/bug?extid=e008db2ac01e282550ee
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=112dca1a580000