[syzbot] [btrfs?] KMSAN: uninit-value in btrfs_compress_heuristic

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 614da38e2f7a Merge tag 'hid-for-linus-2024051401' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14573014980000
kernel config: https://syzkaller.appspot.com/x/.config?x=f5d2cbf33633f507
dashboard link: https://syzkaller.appspot.com/bug?extid=ca895d3f00092ebf1408
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/89eafb874b71/disk-614da38e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/356000512ad9/vmlinux-614da38e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/839c73939115/bzImage-614da38e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ca895d...@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in btrfs_compress_heuristic+0xb34/0x31f0 fs/btrfs/compression.c:1507
btrfs_compress_heuristic+0xb34/0x31f0 fs/btrfs/compression.c:1507
inode_need_compress fs/btrfs/inode.c:812 [inline]
btrfs_run_delalloc_range+0x158f/0x16e0 fs/btrfs/inode.c:2281
writepage_delalloc+0x244/0x6b0 fs/btrfs/extent_io.c:1213
__extent_writepage fs/btrfs/extent_io.c:1465 [inline]
extent_write_cache_pages fs/btrfs/extent_io.c:2142 [inline]
extent_writepages+0x1c01/0x3850 fs/btrfs/extent_io.c:2264
btrfs_writepages+0x35/0x40 fs/btrfs/inode.c:7929
do_writepages+0x427/0xc30 mm/page-writeback.c:2613
filemap_fdatawrite_wbc+0x1d8/0x270 mm/filemap.c:397
start_delalloc_inodes+0xb02/0x17c0 fs/btrfs/inode.c:9404
btrfs_start_delalloc_roots+0x89e/0x1030 fs/btrfs/inode.c:9481
shrink_delalloc fs/btrfs/space-info.c:648 [inline]
flush_space+0xbd6/0x16d0 fs/btrfs/space-info.c:758
btrfs_async_reclaim_metadata_space+0x76d/0x9c0 fs/btrfs/space-info.c:1088
process_one_work kernel/workqueue.c:3267 [inline]
process_scheduled_works+0xa81/0x1bd0 kernel/workqueue.c:3348
worker_thread+0xea5/0x1560 kernel/workqueue.c:3429
kthread+0x3e2/0x540 kernel/kthread.c:389
ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Uninit was stored to memory at:
heuristic_collect_sample fs/btrfs/compression.c:1461 [inline]
btrfs_compress_heuristic+0x303/0x31f0 fs/btrfs/compression.c:1496
inode_need_compress fs/btrfs/inode.c:812 [inline]
btrfs_run_delalloc_range+0x158f/0x16e0 fs/btrfs/inode.c:2281
writepage_delalloc+0x244/0x6b0 fs/btrfs/extent_io.c:1213
__extent_writepage fs/btrfs/extent_io.c:1465 [inline]
extent_write_cache_pages fs/btrfs/extent_io.c:2142 [inline]
extent_writepages+0x1c01/0x3850 fs/btrfs/extent_io.c:2264
btrfs_writepages+0x35/0x40 fs/btrfs/inode.c:7929
do_writepages+0x427/0xc30 mm/page-writeback.c:2613
filemap_fdatawrite_wbc+0x1d8/0x270 mm/filemap.c:397
start_delalloc_inodes+0xb02/0x17c0 fs/btrfs/inode.c:9404
btrfs_start_delalloc_roots+0x89e/0x1030 fs/btrfs/inode.c:9481
shrink_delalloc fs/btrfs/space-info.c:648 [inline]
flush_space+0xbd6/0x16d0 fs/btrfs/space-info.c:758
btrfs_async_reclaim_metadata_space+0x76d/0x9c0 fs/btrfs/space-info.c:1088
process_one_work kernel/workqueue.c:3267 [inline]
process_scheduled_works+0xa81/0x1bd0 kernel/workqueue.c:3348
worker_thread+0xea5/0x1560 kernel/workqueue.c:3429
kthread+0x3e2/0x540 kernel/kthread.c:389
ret_from_fork+0x6d/0x90 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Uninit was stored to memory at:
memcpy_from_iter lib/iov_iter.c:73 [inline]
iterate_bvec include/linux/iov_iter.h:122 [inline]
iterate_and_advance2 include/linux/iov_iter.h:249 [inline]
iterate_and_advance include/linux/iov_iter.h:271 [inline]
__copy_from_iter lib/iov_iter.c:249 [inline]
copy_page_from_iter_atomic+0x12b7/0x2ae0 lib/iov_iter.c:481
btrfs_copy_from_user+0x176/0x4c0 fs/btrfs/file.c:59
btrfs_buffered_write+0x119a/0x2ab0 fs/btrfs/file.c:1339
btrfs_do_write_iter+0x395/0x2270 fs/btrfs/file.c:1688
btrfs_file_write_iter+0x38/0x50 fs/btrfs/file.c:1705
__kernel_write_iter+0x64d/0xc80 fs/read_write.c:523
dump_emit_page fs/coredump.c:895 [inline]
dump_user_range+0x8dc/0xee0 fs/coredump.c:956
elf_core_dump+0x57c7/0x5ae0 fs/binfmt_elf.c:2083
do_coredump+0x32d5/0x4920 fs/coredump.c:769
get_signal+0x267e/0x2d00 kernel/signal.c:2896
arch_do_signal_or_restart+0x53/0xcb0 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x5d/0x160 kernel/entry/common.c:218
do_syscall_64+0xdc/0x1e0 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
__alloc_pages+0x9d6/0xe70 mm/page_alloc.c:4598
alloc_pages_mpol+0x299/0x990 mm/mempolicy.c:2264
alloc_pages+0x1bf/0x1e0 mm/mempolicy.c:2335
dump_user_range+0x4a/0xee0 fs/coredump.c:940
elf_core_dump+0x57c7/0x5ae0 fs/binfmt_elf.c:2083
do_coredump+0x32d5/0x4920 fs/coredump.c:769
get_signal+0x267e/0x2d00 kernel/signal.c:2896
arch_do_signal_or_restart+0x53/0xcb0 arch/x86/kernel/signal.c:310
exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:328 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0x5d/0x160 kernel/entry/common.c:218
do_syscall_64+0xdc/0x1e0 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 PID: 3751 Comm: kworker/u8:28 Not tainted 6.9.0-syzkaller-02707-g614da38e2f7a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Workqueue: events_unbound btrfs_async_reclaim_metadata_space
=====================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup