Re: [syzbot] Re: [syzbot] [fuse?] KASAN: null-ptr-deref Read in fuse_copy_do

[syzbot <syzbot+87b8e6ed25dbc41759f7@syzkaller.appspotmail.com>]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: Re: [syzbot] [fuse?] KASAN: null-ptr-deref Read in fuse_copy_do
Author: bernd.schubert@fastmail.fm

#syz test: https://github.com/bsbernd/linux folio-syzbot-debug


On 11/27/24 19:04, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    445d9f05fa14 Merge tag 'nfsd-6.13' of git://git.kernel.org..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=12733530580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=3c44a32edb32752c
> dashboard link: https://syzkaller.appspot.com/bug?extid=87b8e6ed25dbc41759f7
> compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11fd43c0580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15cf2f5f980000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/9fd8dd2a6550/disk-445d9f05.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/af034d90afcb/vmlinux-445d9f05.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/07a713832258/bzImage-445d9f05.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+87b8e6ed25dbc41759f7@syzkaller.appspotmail.com
> 
> ==================================================================
> BUG: KASAN: null-ptr-deref in fuse_copy_do+0x183/0x320 fs/fuse/dev.c:809
> Write of size 5 at addr 0000000000000000 by task syz-executor159/5840
> 
> CPU: 0 UID: 0 PID: 5840 Comm: syz-executor159 Not tainted 6.12.0-syzkaller-09734-g445d9f05fa14 #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> Call Trace:
>  <TASK>
>  __dump_stack lib/dump_stack.c:94 [inline]
>  dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
>  kasan_report+0xd9/0x110 mm/kasan/report.c:602
>  check_region_inline mm/kasan/generic.c:183 [inline]
>  kasan_check_range+0xef/0x1a0 mm/kasan/generic.c:189
>  __asan_memcpy+0x3c/0x60 mm/kasan/shadow.c:106
>  fuse_copy_do+0x183/0x320 fs/fuse/dev.c:809
>  fuse_copy_one fs/fuse/dev.c:1065 [inline]
>  fuse_copy_args+0x1e6/0x770 fs/fuse/dev.c:1083
>  copy_out_args fs/fuse/dev.c:1966 [inline]
>  fuse_dev_do_write+0x1cc1/0x3720 fs/fuse/dev.c:2052
>  fuse_dev_write+0x14f/0x1e0 fs/fuse/dev.c:2087
>  new_sync_write fs/read_write.c:586 [inline]
>  vfs_write+0x5ae/0x1150 fs/read_write.c:679
>  ksys_write+0x12b/0x250 fs/read_write.c:731
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fa4c9df3c0f
> Code: 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 89 5e 02 00 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 31 44 89 c7 48 89 44 24 08 e8 dc 5e 02 00 48
> RSP: 002b:00007fa4c9da71e0 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
> RAX: ffffffffffffffda RBX: 00007fa4c9e7f3e8 RCX: 00007fa4c9df3c0f
> RDX: 0000000000000015 RSI: 0000000020000540 RDI: 0000000000000003
> RBP: 00007fa4c9e7f3e0 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000293 R12: 00007fa4c9e4c33c
> R13: 00007fa4c9e44027 R14: 00007fff3bcf2380 R15: 00007fa4c9e4a338
>  </TASK>
> ==================================================================
> 
> 
> ---
> 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 syzkaller@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 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.
> 
> 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
>