Re: [syzbot] [fs?] KMSAN: uninit-value in full_proxy_poll

[Charalampos Mitrodimas]

On 3/2/25 3:14 AM, syzbot wrote:
> 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=146c5ddf980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=7d0bb5e08cf54aa2
> dashboard link: https://syzkaller.appspot.com/bug?extid=a84ce0b8e1f3da037bf7
> 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=10cb8518580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=122a0b24580000
>
> 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+a84ce0b8e1f3da037bf7@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> =====================================================
> BUG: KMSAN: uninit-value in full_proxy_poll+0xdf/0x3b0 fs/debugfs/file.c:411
>   full_proxy_poll+0xdf/0x3b0 fs/debugfs/file.c:411
>   vfs_poll include/linux/poll.h:82 [inline]
>   ep_item_poll fs/eventpoll.c:1060 [inline]
>   ep_insert+0x19c7/0x2740 fs/eventpoll.c:1736
>   do_epoll_ctl+0xd83/0x17f0 fs/eventpoll.c:2394
>   __do_sys_epoll_ctl fs/eventpoll.c:2445 [inline]
>   __se_sys_epoll_ctl fs/eventpoll.c:2436 [inline]
>   __x64_sys_epoll_ctl+0x1b5/0x210 fs/eventpoll.c:2436
>   x64_sys_call+0x1658/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:234
>   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+0xe86/0xef0 fs/debugfs/file.c:122
>   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+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: 0 UID: 0 PID: 5778 Comm: syz-executor303 Not tainted 6.13.0-syzkaller-09585-gb4b0881156fb #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 12/27/2024
> =====================================================
>
>
> ---
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>
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>
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>
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>
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>
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>
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|#syz test: |git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git|57b314752ec0ad42685bc78b376326f1f4c04669|