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

[syzbot <syzbot+63ba511937b4080e2ff3@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    bcc8eda6d349 Merge tag 'turbostat-2024.11.30' of git://git..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15ad15e8580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=53ebff8e07a0ee6f
dashboard link: https://syzkaller.appspot.com/bug?extid=63ba511937b4080e2ff3
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/63b4b090e8f0/disk-bcc8eda6.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c1f37f73b54c/vmlinux-bcc8eda6.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9c076d69bc6d/bzImage-bcc8eda6.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+63ba511937b4080e2ff3@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: null-ptr-deref in fuse_copy_one fs/fuse/dev.c:1065 [inline]
BUG: KASAN: null-ptr-deref in fuse_copy_args+0x2d8/0x9c0 fs/fuse/dev.c:1083
Read of size 1 at addr 0000000000000000 by task syz.4.900/10122

CPU: 1 UID: 0 PID: 10122 Comm: syz.4.900 Not tainted 6.12.0-syzkaller-12113-gbcc8eda6d349 #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+0x241/0x360 lib/dump_stack.c:120
 print_report+0xe8/0x550 mm/kasan/report.c:492
 kasan_report+0x143/0x180 mm/kasan/report.c:602
 kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
 __asan_memcpy+0x29/0x70 mm/kasan/shadow.c:105
 fuse_copy_one fs/fuse/dev.c:1065 [inline]
 fuse_copy_args+0x2d8/0x9c0 fs/fuse/dev.c:1083
 fuse_dev_do_read+0xcbd/0x11e0 fs/fuse/dev.c:1357
 fuse_dev_read+0x170/0x220 fs/fuse/dev.c:1424
 new_sync_read fs/read_write.c:484 [inline]
 vfs_read+0x991/0xb70 fs/read_write.c:565
 ksys_read+0x18f/0x2b0 fs/read_write.c:708
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7ff6ba57f25c
Code: ec 28 48 89 54 24 18 48 89 74 24 10 89 7c 24 08 e8 99 8e 02 00 48 8b 54 24 18 48 8b 74 24 10 41 89 c0 8b 7c 24 08 31 c0 0f 05 <48> 3d 00 f0 ff ff 77 34 44 89 c7 48 89 44 24 08 e8 ef 8e 02 00 48
RSP: 002b:00007ff6bb396fd0 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 0000000020002100 RCX: 00007ff6ba57f25c
RDX: 0000000000002000 RSI: 0000000020002100 RDI: 0000000000000003
RBP: 00007ff6ba5f3986 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000003 R11: 0000000000000246 R12: 0000000000000003
R13: 0000000020000c80 R14: 00007ff6ba745fa0 R15: 00007ffecabbe838
 </TASK>
==================================================================


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