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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: e4f7d8be268e Linux 6.1.182
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=131ab679580000
kernel config: https://syzkaller.appspot.com/x/.config?x=872c04466179833f
dashboard link: https://syzkaller.appspot.com/bug?extid=6fae63536adc589b37ec
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
userspace arch: arm64

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7cd9b1875376/disk-e4f7d8be.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4b5d35d18c31/vmlinux-e4f7d8be.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d5ee64c2af77/Image-e4f7d8be.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6fae63...@syzkaller.appspotmail.com

Unable to handle kernel paging request at virtual address dfff800000000000
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
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
[dfff800000000000] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 5492 Comm: syz.6.237 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 22400005 (nzCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : vsscanf+0x170/0x1fe8 lib/vsprintf.c:3446
lr : vsscanf+0x158/0x1fe8 lib/vsprintf.c:3445
sp : ffff800021ae7320
x29: ffff800021ae7400 x28: ffff70000435ce70 x27: ffff800017d37b30
x26: dfff800000000000 x25: ffff800021ae75c0 x24: ffff800011d968c0
x23: 0000000020001840 x22: 0000000000000030 x21: 0000000000000000
x20: 0000000000000004 x19: ffff800013e49760 x18: 0000000000000000
x17: 0000000000000000 x16: ffff800011b90080 x15: 0000000000000002
x14: 0000000000000025 x13: 0000000000ff0100 x12: ffff800017d37b50
x11: ffff0000c6ba1c00 x10: ffff800011a8a6e4 x9 : ffff800011d968c1
x8 : 0000000000000000 x7 : ffff800021ae74a0 x6 : ffff800021ae7580
x5 : ffff800021ae74c0 x4 : ffff800021ae7500 x3 : ffff800011a8c74c
x2 : ffff800021ae74a0 x1 : ffff800017d37b30 x0 : 0000000000000030
Call trace:
vsscanf+0x170/0x1fe8 lib/vsprintf.c:3446
sscanf+0xd8/0x128 lib/vsprintf.c:3704
split_huge_pages_write+0x384/0x163c mm/huge_memory.c:3166
full_proxy_write+0x110/0x1f4 fs/debugfs/file.c:244
do_loop_readv_writev fs/read_write.c:-1 [inline]
do_iter_write+0x3d0/0x93c fs/read_write.c:863
vfs_writev fs/read_write.c:934 [inline]
do_pwritev+0x1e8/0x338 fs/read_write.c:1031
__do_sys_pwritev fs/read_write.c:1078 [inline]
__se_sys_pwritev fs/read_write.c:1073 [inline]
__arm64_sys_pwritev+0xa4/0xbc fs/read_write.c:1073
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x5c/0x134 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: 3400ea36 d343fea8 91000709 f9002fe9 (38fa6908)
---[ end trace 0000000000000000 ]---
pstore: crypto_comp_compress failed, ret = -22!
----------------
Code disassembly (best guess):
0: 3400ea36 cbz w22, 0x1d44
4: d343fea8 lsr x8, x21, #3
8: 91000709 add x9, x24, #0x1
c: f9002fe9 str x9, [sp, #88]
* 10: 38fa6908 ldrsb w8, [x8, x26] <-- trapping instruction


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: e4f7d8be268e Linux 6.1.182
git tree: linux-6.1.y

console output: https://syzkaller.appspot.com/x/log.txt?x=161b4549580000

kernel config: https://syzkaller.appspot.com/x/.config?x=872c04466179833f
dashboard link: https://syzkaller.appspot.com/bug?extid=6fae63536adc589b37ec
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
userspace arch: arm64

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1504e679580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16e976c6580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/7cd9b1875376/disk-e4f7d8be.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4b5d35d18c31/vmlinux-e4f7d8be.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d5ee64c2af77/Image-e4f7d8be.gz.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6fae63...@syzkaller.appspotmail.com

Unable to handle kernel paging request at virtual address dfff800000000000
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
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
[dfff800000000000] address between user and kernel address ranges
Internal error: Oops: 0000000096000006 [#1] PREEMPT SMP
Modules linked in:

CPU: 1 PID: 4508 Comm: syz.0.17 Not tainted syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
pstate: 22400005 (nzCv daif +PAN -UAO +TCO -DIT -SSBS BTYPE=--)
pc : vsscanf+0x170/0x1fe8 lib/vsprintf.c:3446
lr : vsscanf+0x158/0x1fe8 lib/vsprintf.c:3445

sp : ffff8000215f7320
x29: ffff8000215f7400 x28: ffff7000042bee70 x27: ffff800017d37b30
x26: dfff800000000000 x25: ffff8000215f75c0 x24: ffff800011d968c0

x23: 0000000020001840 x22: 0000000000000030 x21: 0000000000000000
x20: 0000000000000004 x19: ffff800013e49760 x18: 0000000000000000

x17: 0000000000000000 x16: ffff800011b90080 x15: 0000000000000000

x14: 0000000000000025 x13: 0000000000ff0100 x12: ffff800017d37b50

x11: ffff0000d2b58000 x10: ffff800011a8a6e4 x9 : ffff800011d968c1
x8 : 0000000000000000 x7 : ffff8000215f74a0 x6 : ffff8000215f7580
x5 : ffff8000215f74c0 x4 : ffff8000215f7500 x3 : ffff800011a8c74c
x2 : ffff8000215f74a0 x1 : ffff800017d37b30 x0 : 0000000000000030

Call trace:
vsscanf+0x170/0x1fe8 lib/vsprintf.c:3446
sscanf+0xd8/0x128 lib/vsprintf.c:3704
split_huge_pages_write+0x384/0x163c mm/huge_memory.c:3166
full_proxy_write+0x110/0x1f4 fs/debugfs/file.c:244
do_loop_readv_writev fs/read_write.c:-1 [inline]
do_iter_write+0x3d0/0x93c fs/read_write.c:863
vfs_writev fs/read_write.c:934 [inline]
do_pwritev+0x1e8/0x338 fs/read_write.c:1031
__do_sys_pwritev fs/read_write.c:1078 [inline]
__se_sys_pwritev fs/read_write.c:1073 [inline]
__arm64_sys_pwritev+0xa4/0xbc fs/read_write.c:1073
__invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
do_el0_svc+0x5c/0x134 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: 3400ea36 d343fea8 91000709 f9002fe9 (38fa6908)
---[ end trace 0000000000000000 ]---

----------------
Code disassembly (best guess):
0: 3400ea36 cbz w22, 0x1d44
4: d343fea8 lsr x8, x21, #3
8: 91000709 add x9, x24, #0x1
c: f9002fe9 str x9, [sp, #88]
* 10: 38fa6908 ldrsb w8, [x8, x26] <-- trapping instruction


---

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.