=====================================================
BUG: KMSAN: uninit-value in iov_iter_alignment_iovec+0x19e/0x470 lib/iov_iter.c:796
 iov_iter_alignment_iovec+0x19e/0x470 lib/iov_iter.c:796
 iov_iter_alignment+0x174/0x2d0 lib/iov_iter.c:841
 check_direct_IO fs/btrfs/direct-io.c:786 [inline]
 check_direct_read fs/btrfs/direct-io.c:1008 [inline]
 btrfs_direct_read+0x2eb/0xcb0 fs/btrfs/direct-io.c:1037
 btrfs_file_read_iter+0xce/0x310 fs/btrfs/file.c:3809
 io_iter_do_read io_uring/rw.c:834 [inline]
 __io_read+0xbf9/0x24b0 io_uring/rw.c:951
 io_read+0x6b/0x3c0 io_uring/rw.c:1031
 __io_issue_sqe+0x2bb/0x790 io_uring/io_uring.c:1824
 io_issue_sqe+0xae/0x1d00 io_uring/io_uring.c:1847
 io_queue_sqe io_uring/io_uring.c:2074 [inline]
 io_submit_sqe io_uring/io_uring.c:2334 [inline]
 io_submit_sqes+0x1252/0x3030 io_uring/io_uring.c:2447
 __do_sys_io_uring_enter io_uring/io_uring.c:3514 [inline]
 __se_sys_io_uring_enter+0x3b7/0x4c30 io_uring/io_uring.c:3453
 __x64_sys_io_uring_enter+0x114/0x1a0 io_uring/io_uring.c:3453
 x64_sys_call+0x3a8c/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:427
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 slab_post_alloc_hook mm/slub.c:4977 [inline]
 slab_alloc_node mm/slub.c:5280 [inline]
 __do_kmalloc_node mm/slub.c:5641 [inline]
 __kmalloc_noprof+0xabb/0x1b40 mm/slub.c:5654
 kmalloc_noprof include/linux/slab.h:961 [inline]
 io_cache_alloc_new+0x55/0x140 io_uring/alloc_cache.c:40
 io_cache_alloc io_uring/alloc_cache.h:59 [inline]
 io_uring_alloc_async_data io_uring/io_uring.h:323 [inline]
 io_rw_alloc_async io_uring/rw.c:202 [inline]
 __io_prep_rw+0x1cd/0x1350 io_uring/rw.c:261
 io_prep_rw io_uring/rw.c:322 [inline]
 io_prep_rwv+0x43/0x5a0 io_uring/rw.c:344
 io_prep_readv+0x38/0x50 io_uring/rw.c:359
 io_init_req io_uring/io_uring.c:2248 [inline]
 io_submit_sqe io_uring/io_uring.c:2295 [inline]
 io_submit_sqes+0x1122/0x3030 io_uring/io_uring.c:2447
 __do_sys_io_uring_enter io_uring/io_uring.c:3514 [inline]
 __se_sys_io_uring_enter+0x3b7/0x4c30 io_uring/io_uring.c:3453
 __x64_sys_io_uring_enter+0x114/0x1a0 io_uring/io_uring.c:3453
 x64_sys_call+0x3a8c/0x3e30 arch/x86/include/generated/asm/syscalls_64.h:427
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0xfa0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 15775 Comm: syz.3.2097 Tainted: G        W           syzkaller #0 PREEMPT(none) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
=====================================================