[syzbot] [ntfs3?] KMSAN: uninit-value in longest_match_std (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 610a9b8f49fb Linux 6.7-rc8
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=11a0f711e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=e51fe20c3e51ba7f
dashboard link: https://syzkaller.appspot.com/bug?extid=08d8956768c96a2c52cf
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=141f845ee80000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1413cf11e80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/28ecdd56de1e/disk-610a9b8f.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3c5afc17c174/vmlinux-610a9b8f.xz
kernel image: https://storage.googleapis.com/syzbot-assets/96ff79b2992d/bzImage-610a9b8f.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/689e00cd89ff/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+08d895...@syzkaller.appspotmail.com

ntfs3: loop0: Failed to initialize $Extend/$ObjId.
=====================================================
BUG: KMSAN: uninit-value in longest_match_std+0x5d9/0xe00 fs/ntfs3/lznt.c:60
longest_match_std+0x5d9/0xe00 fs/ntfs3/lznt.c:60
compress_chunk fs/ntfs3/lznt.c:170 [inline]
compress_lznt+0x41b/0xef0 fs/ntfs3/lznt.c:336
ni_write_frame+0xf89/0x1c80 fs/ntfs3/frecord.c:2839
ntfs_compress_write+0x2521/0x3b70 fs/ntfs3/file.c:995
ntfs_file_write_iter+0x89b/0xd30 fs/ntfs3/file.c:1081
call_write_iter include/linux/fs.h:2020 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x8ef/0x1490 fs/read_write.c:584
ksys_write+0x20f/0x4c0 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__x64_sys_write+0x93/0xd0 fs/read_write.c:646
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was created at:
__alloc_pages+0x9a4/0xe00 mm/page_alloc.c:4591
alloc_pages_mpol+0x62b/0x9d0 mm/mempolicy.c:2133
alloc_pages mm/mempolicy.c:2204 [inline]
folio_alloc+0x1da/0x380 mm/mempolicy.c:2211
filemap_alloc_folio+0xa5/0x430 mm/filemap.c:974
__filemap_get_folio+0xa5a/0x1760 mm/filemap.c:1918
pagecache_get_page+0x4a/0x1a0 mm/folio-compat.c:99
find_or_create_page include/linux/pagemap.h:740 [inline]
ntfs_get_frame_pages+0xdc/0x9f0 fs/ntfs3/file.c:794
ntfs_compress_write+0x1b0b/0x3b70 fs/ntfs3/file.c:944
ntfs_file_write_iter+0x89b/0xd30 fs/ntfs3/file.c:1081
call_write_iter include/linux/fs.h:2020 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x8ef/0x1490 fs/read_write.c:584
ksys_write+0x20f/0x4c0 fs/read_write.c:637
__do_sys_write fs/read_write.c:649 [inline]
__se_sys_write fs/read_write.c:646 [inline]
__x64_sys_write+0x93/0xd0 fs/read_write.c:646
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0x44/0x110 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x63/0x6b

CPU: 0 PID: 4999 Comm: syz-executor227 Not tainted 6.7.0-rc8-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
=====================================================


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