linux-kernel - [syzbot] BUG: unable to handle kernel paging request in bdi_register

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Date:   Sun, 13 Nov 2022 19:22:39 -0800
From:   syzbot <syzbot+2f84b49020438f7a1e54@...kaller.appspotmail.com>
To:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, syzkaller-bugs@...glegroups.com
Subject: [syzbot] BUG: unable to handle kernel paging request in bdi_register_va

Hello,

syzbot found the following issue on:

HEAD commit:    1621b6eaebf7 Merge branch 'for-next/fixes' into for-kernelci
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-kernelci
console output: https://syzkaller.appspot.com/x/log.txt?x=147932c1880000
kernel config:  https://syzkaller.appspot.com/x/.config?x=606e57fd25c5c6cc
dashboard link: https://syzkaller.appspot.com/bug?extid=2f84b49020438f7a1e54
compiler:       Debian clang version 13.0.1-++20220126092033+75e33f71c2da-1~exp1~20220126212112.63, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: arm64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13834435880000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1668d811880000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/82aa7741098d/disk-1621b6ea.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/f6be08c4e4c2/vmlinux-1621b6ea.xz
kernel image: https://storage.googleapis.com/syzbot-assets/296b6946258a/Image-1621b6ea.gz.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/6366d3f12df1/mount_2.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2f84b49020438f7a1e54@...kaller.appspotmail.com

Unable to handle kernel paging request at virtual address 000000d219eb1dcf
Mem abort info:
  ESR = 0x0000000096000004
  EC = 0x25: DABT (current EL), IL = 32 bits
  SET = 0, FnV = 0
  EA = 0, S1PTW = 0
  FSC = 0x04: level 0 translation fault
Data abort info:
  ISV = 0, ISS = 0x00000004
  CM = 0, WnR = 0
user pgtable: 4k pages, 48-bit VAs, pgdp=000000010ebbd000
[000000d219eb1dcf] pgd=0000000000000000, p4d=0000000000000000
Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
Modules linked in:
CPU: 1 PID: 3197 Comm: syz-executor428 Not tainted 6.1.0-rc4-syzkaller-31872-g1621b6eaebf7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/30/2022
pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
pc : bdi_lookup_rb_node mm/backing-dev.c:824 [inline]
pc : bdi_register_va+0x1d4/0x328 mm/backing-dev.c:883
lr : bdi_lookup_rb_node mm/backing-dev.c:820 [inline]
lr : bdi_register_va+0x228/0x328 mm/backing-dev.c:883
sp : ffff80001335ba90
x29: ffff80001335bac0 x28: ffff0000ce994ec0 x27: 0000000000000000
x26: 0000000000008000 x25: 0000000000000000 x24: 0000000000000000
x23: ffff0000cea2f018 x22: 000000d219eb1dd7 x21: 000000d219eb1dd7
x20: 0000000000000040 x19: ffff0000cea29000 x18: 0000000000000322
x17: 4e51455300696462 x16: ffff80000db1a158 x15: ffff0000ce994ec0
x14: 0000000000000050 x13: 00000000ffffffff x12: ffff0000ce994ec0
x11: ff808000084395bc x10: 0000000000000000 x9 : ffff8000084395bc
x8 : ffff0000ce994ec0 x7 : ffff8000084394f8 x6 : 0000000000000000
x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
x2 : 0000000000000001 x1 : 0000000000000040 x0 : 0000000100000010
Call trace:
 bdi_register_va+0x1d4/0x328 mm/backing-dev.c:883
 super_setup_bdi_name+0x84/0x120 fs/super.c:1590
 super_setup_bdi+0x50/0x8c fs/super.c:1612
 v9fs_fill_super fs/9p/vfs_super.c:76 [inline]
 v9fs_mount+0x1a4/0x568 fs/9p/vfs_super.c:137
 legacy_get_tree+0x30/0x74 fs/fs_context.c:610
 vfs_get_tree+0x40/0x140 fs/super.c:1531
 do_new_mount+0x1dc/0x4e4 fs/namespace.c:3040
 path_mount+0x358/0x890 fs/namespace.c:3370
 do_mount fs/namespace.c:3383 [inline]
 __do_sys_mount fs/namespace.c:3591 [inline]
 __se_sys_mount fs/namespace.c:3568 [inline]
 __arm64_sys_mount+0x2c4/0x3c4 fs/namespace.c:3568
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall arch/arm64/kernel/syscall.c:52 [inline]
 el0_svc_common+0x138/0x220 arch/arm64/kernel/syscall.c:142
 do_el0_svc+0x48/0x164 arch/arm64/kernel/syscall.c:206
 el0_svc+0x58/0x150 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:584
Code: f9416116 b4000396 90035097 910b02f7 (f85f82d5) 
---[ end trace 0000000000000000 ]---
----------------
Code disassembly (best guess):
   0:	f9416116 	ldr	x22, [x8, #704]
   4:	b4000396 	cbz	x22, 0x74
   8:	90035097 	adrp	x23, 0x6a10000
   c:	910b02f7 	add	x23, x23, #0x2c0
* 10:	f85f82d5 	ldur	x21, [x22, #-8] <-- trapping instruction


---
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