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

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Message-ID: <6935a9e7.a70a0220.38f243.0065.GAE@google.com>
Date: Sun, 07 Dec 2025 08:23:03 -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

DEBUG: memcg is NULL (memcg_id=0), pgdat=0000000000000000, returning false
DEBUG: shadow=0000000000000013 token=0 workingset=1
BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 36e08067 P4D 36e08067 PUD 0 
Oops: Oops: 0010 [#1] SMP KASAN NOPTI
CPU: 2 UID: 0 PID: 6417 Comm: syz.0.25 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:ffffc9000444f988 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81f7e52e
RDX: ffff888036dfc980 RSI: ffffea00011b2b00 RDI: ffff8880329bbdc0
RBP: ffffea00011b2b00 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 1ffff92000889f32
R13: ffff8880329bbdc0 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007f75eb5a26c0(0000) GS:ffff8880d6b09000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000005576a000 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: 0033:0x7f75ea78f7c9
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:00007f75eb5a2038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f75ea9e5fa0 RCX: 00007f75ea78f7c9
RDX: 0000200000000180 RSI: 00000000c0686611 RDI: 0000000000000003
RBP: 00007f75ea813f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f75ea9e6038 R14: 00007f75ea9e5fa0 R15: 00007fff20402df8
 </TASK>
Modules linked in:
CR2: 0000000000000000
---[ end trace 0000000000000000 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0018:ffffc9000444f988 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81f7e52e
RDX: ffff888036dfc980 RSI: ffffea00011b2b00 RDI: ffff8880329bbdc0
RBP: ffffea00011b2b00 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: 1ffff92000889f32
R13: ffff8880329bbdc0 R14: 0000000000000000 R15: dffffc0000000000
FS:  00007f75eb5a26c0(0000) GS:ffff8880d6b09000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 000000005576a000 CR4: 0000000000352ef0


Tested on:

commit:         9e906a9d Merge tag 'perf-tools-for-v6.19-2025-12-06' o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=162e66c2580000
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=14b1521a580000