[v6.1] BUG: unable to handle kernel paging request in balance_internal

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 1989cd3d56e2 Linux 6.1.167
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1005f06a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b1adc0bfde2d8a4a
dashboard link: https://syzkaller.appspot.com/bug?extid=7a24548bcd165232f4c1
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/edd05d4d1a68/disk-1989cd3d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bdc3181e838d/vmlinux-1989cd3d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a78aef5a3a25/Image-1989cd3d.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7a2454...@syzkaller.appspotmail.com

REISERFS warning (device loop4): vs-13060 reiserfs_update_sd_size: stat data of object [2 2 0x0 SD] (nlink == 1) not found (pos 0)
REISERFS warning (device loop4): vs-13060 reiserfs_update_sd_size: stat data of object [2 2 0x0 SD] (nlink == 1) not found (pos 0)
Unable to handle kernel paging request at virtual address dfff800000000003
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
Mem abort info:
ESR = 0x0000000096000006
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000006
CM = 0, WnR = 0
[dfff800000000003] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 0 PID: 8030 Comm: syz.4.934 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/26/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : balance_internal_when_delete fs/reiserfs/ibalance.c:675 [inline]
pc : balance_internal+0x2238/0x3ee8 fs/reiserfs/ibalance.c:849
lr : balance_internal_when_delete fs/reiserfs/ibalance.c:668 [inline]
lr : balance_internal+0x2210/0x3ee8 fs/reiserfs/ibalance.c:849
sp : ffff8000219b6940
x29: ffff8000219b6b80 x28: ffff700004336d48 x27: dfff800000000000
x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000001
x23: 0000000000000000 x22: 0000000000000018 x21: 0000000000000000
x20: ffff8000219b6da0 x19: ffff0000ffd71740 x18: ffff800011b9bf60
x17: 1fffe00033ea637e x16: ffff8000082d1110 x15: 0000000000000002
x14: 0000000000000001 x13: 1fffe0001ffae2e8 x12: 0000000000080000
x11: 000000000001048d x10: ffff80002ae65000 x9 : ffff800008ccbcb8
x8 : 0000000000000003 x7 : 49ce101f00000213 x6 : 49ce101f00000213
x5 : ffff0000fa59f020 x4 : ffff0000fa59f030 x3 : ffff800008cea2b0
x2 : 0000000000000001 x1 : 0000000000000000 x0 : 0000000000000000
Call trace:
balance_internal_when_delete fs/reiserfs/ibalance.c:675 [inline]
balance_internal+0x2238/0x3ee8 fs/reiserfs/ibalance.c:849
do_balance+0x2b0/0x790 fs/reiserfs/do_balan.c:1896
reiserfs_delete_solid_item+0x750/0xca4 fs/reiserfs/stree.c:1462
remove_save_link+0x1e4/0x350 fs/reiserfs/super.c:540
reiserfs_truncate_file+0x6c0/0xb00 fs/reiserfs/inode.c:2322
reiserfs_setattr+0xab4/0xfec fs/reiserfs/inode.c:3395
notify_change+0xb0c/0xdcc fs/attr.c:499
do_truncate+0x188/0x20c fs/open.c:65
handle_truncate fs/namei.c:3293 [inline]
do_open fs/namei.c:3638 [inline]
path_openat+0x2110/0x26bc fs/namei.c:3791
do_filp_open+0x194/0x384 fs/namei.c:3818
do_sys_openat2+0x134/0x3f4 fs/open.c:1320
do_sys_open fs/open.c:1336 [inline]
__do_sys_openat fs/open.c:1352 [inline]
__se_sys_openat fs/open.c:1347 [inline]
__arm64_sys_openat+0x118/0x14c fs/open.c:1347
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x2b4 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x58/0x130 arch/arm64/kernel/syscall.c:204
el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585
Code: 97f06e0a f94002b5 910062b6 d343fec8 (387b6908)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: 97f06e0a bl 0xffffffffffc1b828
4: f94002b5 ldr x21, [x21]
8: 910062b6 add x22, x21, #0x18
c: d343fec8 lsr x8, x22, #3
* 10: 387b6908 ldrb w8, [x8, x27] <-- trapping instruction


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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 1989cd3d56e2 Linux 6.1.167
git tree: linux-6.1.y

console output: https://syzkaller.appspot.com/x/log.txt?x=126cb3d6580000

kernel config: https://syzkaller.appspot.com/x/.config?x=b1adc0bfde2d8a4a
dashboard link: https://syzkaller.appspot.com/bug?extid=7a24548bcd165232f4c1
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=166cb3d6580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16d4b6ca580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/edd05d4d1a68/disk-1989cd3d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bdc3181e838d/vmlinux-1989cd3d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a78aef5a3a25/Image-1989cd3d.gz.xz

mounted in repro: https://storage.googleapis.com/syzbot-assets/e25f8b79a321/mount_0.gz
fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=115cf5da580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7a2454...@syzkaller.appspotmail.com

REISERFS warning (device loop0): vs-13060 reiserfs_update_sd_size: stat data of object [2 2 0x0 SD] (nlink == 1) not found (pos 0)
REISERFS warning (device loop0): vs-13060 reiserfs_update_sd_size: stat data of object [2 2 0x0 SD] (nlink == 1) not found (pos 0)

Unable to handle kernel paging request at virtual address dfff800000000003
KASAN: null-ptr-deref in range [0x0000000000000018-0x000000000000001f]
Mem abort info:
ESR = 0x0000000096000006
EC = 0x25: DABT (current EL), IL = 32 bits
SET = 0, FnV = 0
EA = 0, S1PTW = 0
FSC = 0x06: level 2 translation fault
Data abort info:
ISV = 0, ISS = 0x00000006
CM = 0, WnR = 0
[dfff800000000003] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:

CPU: 0 PID: 4475 Comm: syz.0.17 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/26/2026
pstate: 82400005 (Nzcv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : balance_internal_when_delete fs/reiserfs/ibalance.c:675 [inline]
pc : balance_internal+0x2238/0x3ee8 fs/reiserfs/ibalance.c:849
lr : balance_internal_when_delete fs/reiserfs/ibalance.c:668 [inline]
lr : balance_internal+0x2210/0x3ee8 fs/reiserfs/ibalance.c:849

sp : ffff800021056940
x29: ffff800021056b80 x28: ffff70000420ad48 x27: dfff800000000000

x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000001
x23: 0000000000000000 x22: 0000000000000018 x21: 0000000000000000

x20: ffff800021056da0 x19: ffff0000c6887488 x18: 0000000000000000
x17: 0000000000000000 x16: ffff8000082d1110 x15: 0000000000000000
x14: 0000000000000001 x13: 1fffe00018d10e91 x12: 0000000000ff0100
x11: ff00800008ccbcb8 x10: 0000000000000000 x9 : ffff800008ccbcb8
x8 : 0000000000000003 x7 : 49ce0fe700000213 x6 : 49ce0fe700000213
x5 : ffff0000e9cdf020 x4 : ffff0000e9cdf030 x3 : ffff800008cea2b0

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.