[syzbot] [fs?] BUG: unable to handle kernel NULL pointer dereference in filemap_read_folio (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 3022e9d00ebe Merge tag 'sched_ext-for-6.12-rc7-fixes' of g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=119f8ce8580000
kernel config: https://syzkaller.appspot.com/x/.config?x=327b6119dd928cbc
dashboard link: https://syzkaller.appspot.com/bug?extid=09b7d050e4806540153d
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1656a4c0580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=159f8ce8580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7feb34a89c2a/non_bootable_disk-3022e9d0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6539389f3983/vmlinux-3022e9d0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9ee2dbf68ed6/bzImage-3022e9d0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+09b7d0...@syzkaller.appspotmail.com

BUG: kernel NULL pointer dereference, address: 0000000000000000
#PF: supervisor instruction fetch in kernel mode
#PF: error_code(0x0010) - not-present page
PGD 32263067 P4D 32263067 PUD 32264067 PMD 0
Oops: Oops: 0010 [#1] PREEMPT SMP KASAN NOPTI
CPU: 3 UID: 0 PID: 5935 Comm: syz-executor262 Not tainted 6.12.0-rc7-syzkaller-00012-g3022e9d00ebe #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0018:ffffc900036a79c8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81c26c1f
RDX: ffff8880289da440 RSI: ffffea0000e995c0 RDI: ffff888029a421c0
RBP: ffffea0000e995c0 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff961d8908 R12: 1ffff920006d4f3a
R13: ffff888029a421c0 R14: 0000000000000000 R15: dffffc0000000000
FS: 000055557e035380(0000) GS:ffff88806a900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 0000000031818000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
filemap_read_folio+0xc6/0x2a0 mm/filemap.c:2367
do_read_cache_folio+0x263/0x5c0 mm/filemap.c:3825
freader_get_folio+0x337/0x8e0 lib/buildid.c:77
freader_fetch+0xc2/0x5f0 lib/buildid.c:120
__build_id_parse.isra.0+0xed/0x7a0 lib/buildid.c:305
do_procmap_query+0xd62/0x1030 fs/proc/task_mmu.c:534
procfs_procmap_ioctl+0x7d/0xb0 fs/proc/task_mmu.c:613
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl fs/ioctl.c:893 [inline]
__x64_sys_ioctl+0x18f/0x220 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5f4c4436e9
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffde11efd68 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007ffde11efd70 RCX: 00007f5f4c4436e9
RDX: 0000000020000180 RSI: 00000000c0686611 RDI: 0000000000000004
RBP: 00007f5f4c4b6610 R08: 0000000000000000 R09: 65732f636f72702f
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007ffde11effa8 R14: 0000000000000001 R15: 0000000000000001
</TASK>
Modules linked in:
CR2: 0000000000000000
---[ end trace 0000000000000000 ]---
RIP: 0010:0x0
Code: Unable to access opcode bytes at 0xffffffffffffffd6.
RSP: 0018:ffffc900036a79c8 EFLAGS: 00010293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81c26c1f
RDX: ffff8880289da440 RSI: ffffea0000e995c0 RDI: ffff888029a421c0
RBP: ffffea0000e995c0 R08: 0000000000000007 R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff961d8908 R12: 1ffff920006d4f3a
R13: ffff888029a421c0 R14: 0000000000000000 R15: dffffc0000000000
FS: 000055557e035380(0000) GS:ffff88806a900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffffffffd6 CR3: 0000000031818000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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[Hillf Danton]

On Sat, 16 Nov 2024 15:40:29 -0800

> syzbot found the following issue on:
>
> HEAD commit: 3022e9d00ebe Merge tag 'sched_ext-for-6.12-rc7-fixes' of g..
> git tree: upstream

> C reproducer: https://syzkaller.appspot.com/x/repro.c?x=159f8ce8580000

#syz test

--- x/mm/filemap.c
+++ y/mm/filemap.c
@@ -3781,6 +3781,8 @@ static struct folio *do_read_cache_folio

if (!filler)
filler = mapping->a_ops->read_folio;
+ if (!filler)
+ return ERR_PTR(-EINVAL);
repeat:
folio = filemap_get_folio(mapping, index);
if (IS_ERR(folio)) {
--

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+09b7d0...@syzkaller.appspotmail.com
Tested-by: syzbot+09b7d0...@syzkaller.appspotmail.com

Tested on:

commit: 4a5df379 Merge tag 'mm-hotfixes-stable-2024-11-16-15-3..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17dc52e8580000
kernel config: https://syzkaller.appspot.com/x/.config?x=4fca5d6b7cd3e6f

dashboard link: https://syzkaller.appspot.com/bug?extid=09b7d050e4806540153d
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=16cc52e8580000

Note: testing is done by a robot and is best-effort only.

[syzbot]

syzbot has bisected this issue to:

commit ad41251c290dfe3c01472c94d2439a59de23fe97
Author: Andrii Nakryiko <and...@kernel.org>
Date: Thu Aug 29 17:42:28 2024 +0000

lib/buildid: implement sleepable build_id_parse() API

bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=1601923f980000
start commit: a2cc6ff5ec8f Merge tag 'firewire-updates-6.15' of git://gi..
git tree: upstream
final oops: https://syzkaller.appspot.com/x/report.txt?x=1501923f980000
console output: https://syzkaller.appspot.com/x/log.txt?x=1101923f980000
kernel config: https://syzkaller.appspot.com/x/.config?x=6fe3b5e6a2cb1cc2
dashboard link: https://syzkaller.appspot.com/bug?extid=09b7d050e4806540153d
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15743998580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10143404580000

Reported-by: syzbot+09b7d0...@syzkaller.appspotmail.com
Fixes: ad41251c290d ("lib/buildid: implement sleepable build_id_parse() API")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection