Re: [syzbot] BUG: unable to handle kernel NULL pointer dereference in do_read_cache_folio

[Dmitry Vyukov]

On Tue, 4 Oct 2022 at 11:53, syzbot
<syzbot+c3616973d9db2b0cff65@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    bbed346d5a96 Merge branch 'for-next/core' 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=120e011f080000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=aae2d21e7dd80684
> dashboard link: https://syzkaller.appspot.com/bug?extid=c3616973d9db2b0cff65
> 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
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/11078f50b80b/disk-bbed346d.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/398e5f1e6c84/vmlinux-bbed346d.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+c3616973d9db2b0cff65@xxxxxxxxxxxxxxxxxxxxxxxxx

+ntfs maintainers

> ntfs: volume version 3.1.
> Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
> Mem abort info:
>   ESR = 0x0000000086000006
>   EC = 0x21: IABT (current EL), IL = 32 bits
>   SET = 0, FnV = 0
>   EA = 0, S1PTW = 0
>   FSC = 0x06: level 2 translation fault
> user pgtable: 4k pages, 48-bit VAs, pgdp=00000001515fb000
> [0000000000000000] pgd=080000015162c003, p4d=080000015162c003, pud=08000001511b5003, pmd=0000000000000000
> Internal error: Oops: 0000000086000006 [#1] PREEMPT SMP
> Modules linked in:
> CPU: 0 PID: 4711 Comm: syz-executor.1 Not tainted 6.0.0-rc7-syzkaller-18095-gbbed346d5a96 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
> pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> pc : 0x0
> lr : filemap_read_folio+0x68/0x33c mm/filemap.c:2394
> sp : ffff800015e03940
> x29: ffff800015e03940 x28: 00000000ffffffff x27: 0000000000080001
> x26: 0000000000001000 x25: 0000000000000000 x24: 0000000000000000
> x23: fffffc00044d8580 x22: fffffc00044d8580 x21: 0000000000000000
> x20: 0000000000000000 x19: fffffc00044d8580 x18: fffffffffffffff5
> x17: ffff80000bffd6bc x16: 0000000000000068 x15: 000000000000000c
> x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000004
> x11: ff808000083d0b00 x10: 0000000000000000 x9 : ffff8000083d0b00
> x8 : 0000000000000100 x7 : ffff80000818d174 x6 : ffff8000083ed3f0
> x5 : 0000000000000000 x4 : 0000000000000001 x3 : 0000000000000000
> x2 : fffffc00044d8580 x1 : fffffc00044d8580 x0 : 0000000000000000
> Call trace:
>  0x0
>  do_read_cache_folio+0x1c8/0x588 mm/filemap.c:3519
>  do_read_cache_page mm/filemap.c:3561 [inline]
>  read_cache_page+0x40/0x178 mm/filemap.c:3570
>  read_mapping_page include/linux/pagemap.h:756 [inline]
>  ntfs_map_page fs/ntfs/aops.h:75 [inline]
>  ntfs_check_logfile+0x2a4/0x8cc fs/ntfs/logfile.c:532
>  load_and_check_logfile+0x5c/0xcc fs/ntfs/super.c:1215
>  load_system_files+0x7d0/0x1220 fs/ntfs/super.c:1941
>  ntfs_fill_super+0xbac/0x1030 fs/ntfs/super.c:2891
>  mount_bdev+0x1b8/0x210 fs/super.c:1400
>  ntfs_mount+0x44/0x58 fs/ntfs/super.c:3048
>  legacy_get_tree+0x30/0x74 fs/fs_context.c:610
>  vfs_get_tree+0x40/0x140 fs/super.c:1530
>  do_new_mount+0x1dc/0x4e4 fs/namespace.c:3040
>  path_mount+0x358/0x914 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:636
>  el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:654
>  el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:581
> Code: bad PC value
> ---[ end trace 0000000000000000 ]---
>
>
> ---
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