[syzbot] [ntfs3?] KMSAN: uninit-value in ntfs_iomap_begin

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d79526b89571 Merge tag 'spi-fix-v7.0-merge-window' of git:..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17c90006580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e9e76fdaa4072fa5
dashboard link: https://syzkaller.appspot.com/bug?extid=7be88937363ac7ab7bb0
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1016255a580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16197c02580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9632d1edcebe/disk-d79526b8.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/c9f69df31226/vmlinux-d79526b8.xz
kernel image: https://storage.googleapis.com/syzbot-assets/54f77eae730c/bzImage-d79526b8.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/62ad4352d8b0/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7be889...@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 4096
ntfs3(loop0): Different NTFS sector size (2048) and media sector size (512).
=====================================================
BUG: KMSAN: uninit-value in ntfs_iomap_begin+0x8c0/0x1460 fs/ntfs3/inode.c:825
ntfs_iomap_begin+0x8c0/0x1460 fs/ntfs3/inode.c:825
iomap_iter+0x9b7/0x1540 fs/iomap/iter.c:110
iomap_read_folio+0x262/0x750 fs/iomap/buffered-io.c:587
ntfs_read_folio+0x74a/0x770 fs/ntfs3/inode.c:697
filemap_read_folio mm/filemap.c:2496 [inline]
do_read_cache_folio+0x993/0x1470 mm/filemap.c:4096
do_read_cache_page mm/filemap.c:4162 [inline]
read_cache_page+0x63/0x1e0 mm/filemap.c:4171
read_mapping_page include/linux/pagemap.h:1022 [inline]
inode_read_data+0xb3/0x6b0 fs/ntfs3/inode.c:1116
ntfs_fill_super+0x6a24/0x7e50 fs/ntfs3/super.c:1549
get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
get_tree_bdev+0x38/0x50 fs/super.c:1717
ntfs_fs_get_tree+0x35/0x40 fs/ntfs3/super.c:1788
vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
do_new_mount_fc fs/namespace.c:3760 [inline]
do_new_mount+0x885/0x1dd0 fs/namespace.c:3836
path_mount+0x7a2/0x20b0 fs/namespace.c:4146
do_mount fs/namespace.c:4159 [inline]
__do_sys_mount fs/namespace.c:4348 [inline]
__se_sys_mount+0x704/0x7f0 fs/namespace.c:4325
__x64_sys_mount+0xe4/0x150 fs/namespace.c:4325
x64_sys_call+0x39f0/0x3ea0 arch/x86/include/generated/asm/syscalls_64.h:166
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x134/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Local variable lcn created at:
ntfs_iomap_begin+0x15d/0x1460 fs/ntfs3/inode.c:786
iomap_iter+0x9b7/0x1540 fs/iomap/iter.c:110

CPU: 1 UID: 0 PID: 6051 Comm: syz.0.17 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
=====================================================


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