=====================================================
BUG: KMSAN: uninit-value in iov_iter_alignment_iovec+0x1a8/0x470 lib/iov_iter.c:892
 iov_iter_alignment_iovec+0x1a8/0x470 lib/iov_iter.c:892
 iov_iter_alignment+0x1ac/0x2d0 lib/iov_iter.c:937
 __blockdev_direct_IO+0x170/0x6460 fs/direct-io.c:1121
 blockdev_direct_IO include/linux/fs.h:3280 [inline]
 exfat_direct_IO+0x191/0x900 fs/exfat/inode.c:482
 generic_file_direct_write+0x275/0x6a0 mm/filemap.c:3977
 __generic_file_write_iter+0x242/0x460 mm/filemap.c:4141
 exfat_file_write_iter+0x894/0xfb0 fs/exfat/file.c:598
 io_write+0xbd3/0x20a0 io_uring/rw.c:1059
 io_issue_sqe+0x429/0x22c0 io_uring/io_uring.c:1739
 io_queue_sqe io_uring/io_uring.c:1953 [inline]
 io_submit_sqe io_uring/io_uring.c:2209 [inline]
 io_submit_sqes+0x125c/0x2f30 io_uring/io_uring.c:2324
 __do_sys_io_uring_enter io_uring/io_uring.c:3343 [inline]
 __se_sys_io_uring_enter+0x406/0x41c0 io_uring/io_uring.c:3279
 __x64_sys_io_uring_enter+0x11f/0x1a0 io_uring/io_uring.c:3279
 x64_sys_call+0x2b54/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:427
 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:4091 [inline]
 slab_alloc_node mm/slub.c:4134 [inline]
 __do_kmalloc_node mm/slub.c:4263 [inline]
 __kmalloc_noprof+0x661/0xf30 mm/slub.c:4276
 kmalloc_noprof include/linux/slab.h:882 [inline]
 io_alloc_async_data+0xc0/0x220 io_uring/io_uring.c:1650
 io_rw_alloc_async io_uring/rw.c:228 [inline]
 io_prep_rw_setup io_uring/rw.c:245 [inline]
 io_prep_rw+0x921/0xcd0 io_uring/rw.c:286
 io_prep_rwv+0xb3/0x4e0 io_uring/rw.c:305
 io_prep_writev+0x3a/0x50 io_uring/rw.c:325
 io_init_req io_uring/io_uring.c:2124 [inline]
 io_submit_sqe io_uring/io_uring.c:2171 [inline]
 io_submit_sqes+0x112e/0x2f30 io_uring/io_uring.c:2324
 __do_sys_io_uring_enter io_uring/io_uring.c:3343 [inline]
 __se_sys_io_uring_enter+0x406/0x41c0 io_uring/io_uring.c:3279
 __x64_sys_io_uring_enter+0x11f/0x1a0 io_uring/io_uring.c:3279
 x64_sys_call+0x2b54/0x3ba0 arch/x86/include/generated/asm/syscalls_64.h:427
 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: 13472 Comm: syz.4.1724 Tainted: G        W          6.12.0-rc3-syzkaller-00087-gc964ced77262 #0
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
=====================================================