[syzbot] [kernel?] BUG: unable to handle kernel paging request in subdev_8255_io
From: syzbot
Date: Mon Jul 07 2025 - 12:31:56 EST
Hello,
syzbot found the following issue on:
HEAD commit: a79a588fc176 Merge tag 'pm-6.16-rc5' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17e21c8c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=729bc2714205b7c8
dashboard link: https://syzkaller.appspot.com/bug?extid=f7ad508e3c76c097483f
compiler: arm-linux-gnueabi-gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
userspace arch: arm
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=10e6cf70580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10121c8c580000
Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/98a89b9f34e4/non_bootable_disk-a79a588f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bf35a246f739/vmlinux-a79a588f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8e0e99375077/zImage-a79a588f.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f7ad508e3c76c097483f@xxxxxxxxxxxxxxxxxxxxxxxxx
8<--- cut here ---
Unable to handle kernel paging request at virtual address fee0000f when write
[fee0000f] *pgd=80000080007003, *pmd=00000000
Internal error: Oops: a06 [#1] SMP ARM
Modules linked in:
CPU: 1 UID: 0 PID: 4085 Comm: syz.2.16 Not tainted 6.16.0-rc4-syzkaller #0 PREEMPT
Hardware name: ARM-Versatile Express
PC is at __raw_writeb arch/arm/include/asm/io.h:88 [inline]
PC is at subdev_8255_io drivers/comedi/drivers/comedi_8255.c:47 [inline]
PC is at subdev_8255_io+0x60/0x6c drivers/comedi/drivers/comedi_8255.c:43
LR is at subdev_8255_io drivers/comedi/drivers/comedi_8255.c:47 [inline]
LR is at subdev_8255_io+0x4c/0x6c drivers/comedi/drivers/comedi_8255.c:43
pc : [<813a5ab0>] lr : [<813a5a9c>] psr: 60000013
sp : dfc95cc0 ip : dfc95cc0 fp : dfc95cdc
r10: 00000000 r9 : 00000000 r8 : 00000084
r7 : 0000000c r6 : 0000009b r5 : 84064900 r4 : 0000000f
r3 : 0000009b r2 : fee0000f r1 : 00000001 r0 : 84064900
Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none
Control: 30c5387d Table: 848edb00 DAC: 00000000
Register r0 information: slab kmalloc-192 start 84064900 pointer offset 0 size 192
Register r1 information: non-paged memory
Register r2 information: 0-page vmalloc region starting at 0xfee00000 allocated at pci_reserve_io+0x0/0x38 arch/arm/mm/mmu.c:1055
Register r3 information: non-paged memory
Register r4 information: non-paged memory
Register r5 information: slab kmalloc-192 start 84064900 pointer offset 0 size 192
Register r6 information: non-paged memory
Register r7 information: non-paged memory
Register r8 information: non-paged memory
Register r9 information: NULL pointer
Register r10 information: NULL pointer
Register r11 information: 2-page vmalloc region starting at 0xdfc94000 allocated at kernel_clone+0xac/0x3e4 kernel/fork.c:2599
Register r12 information: 2-page vmalloc region starting at 0xdfc94000 allocated at kernel_clone+0xac/0x3e4 kernel/fork.c:2599
Process syz.2.16 (pid: 4085, stack limit = 0xdfc94000)
Stack: (0xdfc95cc0 to 0xdfc96000)
5cc0: 813a5a50 84064900 0000000c 0000000c dfc95cfc dfc95ce0 813a5788 813a5a5c
5ce0: 0000000c 80508714 85761800 85761800 dfc95d1c dfc95d00 813a5b48 813a573c
5d00: 85761800 84064900 dfc95dac 0000000c dfc95d5c dfc95d20 813a5d3c 813a5ac8
5d20: 20000013 8543a780 82822670 00000000 00000000 829c52b0 84064900 00000000
5d40: dfc95d98 84064900 00000000 82b15078 dfc95d94 dfc95d60 81394c60 813a5c8c
5d60: 20000140 00000000 dfc95d84 20000140 84064900 b5403587 20000140 85400c00
5d80: 40946400 00000003 dfc95e4c dfc95d98 813908f0 81394b68 35353238 00000000
5da0: 00000000 00000000 00000000 0000000c 00002166 00000002 00000010 000088d6
5dc0: 00000b45 00000008 00000010 00000000 ffffffff 00000200 00000fff 00000344
5de0: 00000001 00000002 00000200 00000009 00000003 00000003 00000001 00000004
5e00: 00000000 00000080 00000004 00000001 00000001 0000b0c4 000007df 00000008
5e20: 000000f3 00000001 00000000 4c54bfda 00000000 8497b000 84064900 20000140
5e40: dfc95f14 dfc95e50 813918a4 81390824 00000000 00000000 00000000 4c54bfda
5e60: 00000000 00000000 8246a3fc 0000005f 83ec1858 84064930 842b4174 85400c00
5e80: dfc95ee4 dfc95e90 8079688c 8078cb7c 00000064 00000001 00000000 dfc95eac
5ea0: 85639850 8342b5d8 00006400 0000000b dfc95ea0 00000000 00000000 4c54bfda
5ec0: 8497b000 40946400 20000140 20000140 00000003 8497b000 dfc95ef4 dfc95ee8
5ee0: 807969ac 4c54bfda dfc95f14 40946400 00000000 8497b000 20000140 00000003
5f00: 8497b000 85400c00 dfc95fa4 dfc95f18 8056f16c 813912d4 dfc95f4c dfc95f28
5f20: 80349a98 8034cdb4 81a2db68 81a2da38 dfc95f54 dfc95f40 8026203c 7edec920
5f40: dfc95fa4 dfc95f50 8034a2e0 803499a4 00000000 7edec920 ffffffff 80234128
5f60: 00000000 00000000 00000000 00000000 00000000 4c54bfda dfc95fac 00000000
5f80: 00000000 002f6300 00000036 8020029c 85400c00 00000036 00000000 dfc95fa8
5fa0: 80200060 8056f048 00000000 00000000 00000003 40946400 20000140 00000000
5fc0: 00000000 00000000 002f6300 00000036 00000000 002f62d4 0000047b 00000000
5fe0: 7edec780 7edec770 000193a4 00131f40 60000010 00000003 00000000 00000000
Call trace:
[<813a5a50>] (subdev_8255_io) from [<813a5788>] (subdev_8255_do_config+0x58/0x60 drivers/comedi/drivers/comedi_8255.c:115)
r7:0000000c r6:0000000c r5:84064900 r4:813a5a50
[<813a5730>] (subdev_8255_do_config) from [<813a5b48>] (__subdev_8255_init drivers/comedi/drivers/comedi_8255.c:172 [inline])
[<813a5730>] (subdev_8255_do_config) from [<813a5b48>] (subdev_8255_io_init+0x8c/0x9c drivers/comedi/drivers/comedi_8255.c:192)
r4:85761800
[<813a5abc>] (subdev_8255_io_init) from [<813a5d3c>] (dev_8255_attach drivers/comedi/drivers/8255.c:83 [inline])
[<813a5abc>] (subdev_8255_io_init) from [<813a5d3c>] (dev_8255_attach+0xbc/0x114 drivers/comedi/drivers/8255.c:46)
r7:0000000c r6:dfc95dac r5:84064900 r4:85761800
[<813a5c80>] (dev_8255_attach) from [<81394c60>] (comedi_device_attach+0x104/0x240 drivers/comedi/drivers.c:996)
r10:82b15078 r9:00000000 r8:84064900 r7:dfc95d98 r6:00000000 r5:84064900
r4:829c52b0
[<81394b5c>] (comedi_device_attach) from [<813908f0>] (do_devconfig_ioctl+0xd8/0x1e0 drivers/comedi/comedi_fops.c:855)
r10:00000003 r9:40946400 r8:85400c00 r7:20000140 r6:b5403587 r5:84064900
r4:20000140
[<81390818>] (do_devconfig_ioctl) from [<813918a4>] (comedi_unlocked_ioctl+0x5dc/0x1b94 drivers/comedi/comedi_fops.c:2136)
r6:20000140 r5:84064900 r4:8497b000
[<813912c8>] (comedi_unlocked_ioctl) from [<8056f16c>] (vfs_ioctl fs/ioctl.c:51 [inline])
[<813912c8>] (comedi_unlocked_ioctl) from [<8056f16c>] (do_vfs_ioctl fs/ioctl.c:861 [inline])
[<813912c8>] (comedi_unlocked_ioctl) from [<8056f16c>] (__do_sys_ioctl fs/ioctl.c:905 [inline])
[<813912c8>] (comedi_unlocked_ioctl) from [<8056f16c>] (sys_ioctl+0x130/0xdc8 fs/ioctl.c:893)
r10:85400c00 r9:8497b000 r8:00000003 r7:20000140 r6:8497b000 r5:00000000
r4:40946400
[<8056f03c>] (sys_ioctl) from [<80200060>] (ret_fast_syscall+0x0/0x1c arch/arm/mm/proc-v7.S:67)
Exception stack(0xdfc95fa8 to 0xdfc95ff0)
5fa0: 00000000 00000000 00000003 40946400 20000140 00000000
5fc0: 00000000 00000000 002f6300 00000036 00000000 002f62d4 0000047b 00000000
5fe0: 7edec780 7edec770 000193a4 00131f40
r10:00000036 r9:85400c00 r8:8020029c r7:00000036 r6:002f6300 r5:00000000
r4:00000000
Code: e6ef3076 e0842002 e7f32052 e2422612 (e5c23000)
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
0: e6ef3076 uxtb r3, r6
4: e0842002 add r2, r4, r2
8: e7f32052 ubfx r2, r2, #0, #20
c: e2422612 sub r2, r2, #18874368 @ 0x1200000
* 10: e5c23000 strb r3, [r2] <-- trapping instruction
---
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