[syzbot] [fs?] KMSAN: uninit-value in full_proxy_unlocked_ioctl

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    b4b0881156fb Merge tag 'docs-6.14-2' of git://git.lwn.net/..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=12a04518580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7d0bb5e08cf54aa2
dashboard link: https://syzkaller.appspot.com/bug?extid=8928e473a91452caca2f
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=150776b0580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16aaab64580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4dbe3cd3dcb8/disk-b4b08811.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/592d90859f86/vmlinux-b4b08811.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4cfde2b63c7f/bzImage-b4b08811.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8928e473a91452caca2f@xxxxxxxxxxxxxxxxxxxxxxxxx

=====================================================
BUG: KMSAN: uninit-value in full_proxy_unlocked_ioctl+0xed/0x3a0 fs/debugfs/file.c:399
 full_proxy_unlocked_ioctl+0xed/0x3a0 fs/debugfs/file.c:399
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:906 [inline]
 __se_sys_ioctl+0x246/0x440 fs/ioctl.c:892
 __x64_sys_ioctl+0x96/0xe0 fs/ioctl.c:892
 x64_sys_call+0x19f0/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:17
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was stored to memory at:
 __debugfs_file_get+0xe59/0xef0 fs/debugfs/file.c:120
 full_proxy_open_regular+0x67/0xa00 fs/debugfs/file.c:447
 do_dentry_open+0x1bdd/0x26b0 fs/open.c:955
 vfs_open+0x53/0x5b0 fs/open.c:1085
 do_open fs/namei.c:3830 [inline]
 path_openat+0x56a1/0x6250 fs/namei.c:3989
 do_filp_open+0x268/0x600 fs/namei.c:4016
 do_sys_openat2+0x1bf/0x2f0 fs/open.c:1427
 do_sys_open fs/open.c:1442 [inline]
 __do_sys_openat fs/open.c:1458 [inline]
 __se_sys_openat fs/open.c:1453 [inline]
 __x64_sys_openat+0x2a1/0x310 fs/open.c:1453
 x64_sys_call+0x36f5/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was stored to memory at:
 __debugfs_file_get+0xdff/0xef0 fs/debugfs/file.c:118
 full_proxy_open_regular+0x67/0xa00 fs/debugfs/file.c:447
 do_dentry_open+0x1bdd/0x26b0 fs/open.c:955
 vfs_open+0x53/0x5b0 fs/open.c:1085
 do_open fs/namei.c:3830 [inline]
 path_openat+0x56a1/0x6250 fs/namei.c:3989
 do_filp_open+0x268/0x600 fs/namei.c:4016
 do_sys_openat2+0x1bf/0x2f0 fs/open.c:1427
 do_sys_open fs/open.c:1442 [inline]
 __do_sys_openat fs/open.c:1458 [inline]
 __se_sys_openat fs/open.c:1453 [inline]
 __x64_sys_openat+0x2a1/0x310 fs/open.c:1453
 x64_sys_call+0x36f5/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4121 [inline]
 slab_alloc_node mm/slub.c:4164 [inline]
 __kmalloc_cache_noprof+0x8e3/0xdf0 mm/slub.c:4320
 kmalloc_noprof include/linux/slab.h:901 [inline]
 __debugfs_file_get+0x31d/0xef0 fs/debugfs/file.c:101
 full_proxy_open_regular+0x67/0xa00 fs/debugfs/file.c:447
 do_dentry_open+0x1bdd/0x26b0 fs/open.c:955
 vfs_open+0x53/0x5b0 fs/open.c:1085
 do_open fs/namei.c:3830 [inline]
 path_openat+0x56a1/0x6250 fs/namei.c:3989
 do_filp_open+0x268/0x600 fs/namei.c:4016
 do_sys_openat2+0x1bf/0x2f0 fs/open.c:1427
 do_sys_open fs/open.c:1442 [inline]
 __do_sys_openat fs/open.c:1458 [inline]
 __se_sys_openat fs/open.c:1453 [inline]
 __x64_sys_openat+0x2a1/0x310 fs/open.c:1453
 x64_sys_call+0x36f5/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1e0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 5781 Comm: syz-executor325 Not tainted 6.13.0-syzkaller-09585-gb4b0881156fb #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
=====================================================


---
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@xxxxxxxxxxxxxxxx.

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