[syzbot] [bcachefs?] KMSAN: uninit-value in bch2_extent_crc_append (2)

From: syzbot
Date: Sat Mar 08 2025 - 23:20:39 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 48a5eed9ad58 Merge tag 'devicetree-fixes-for-6.14-2' of gi..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10a275a8580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1d47ea4b9912d894
dashboard link: https://syzkaller.appspot.com/bug?extid=79e4e34c2a37d5a9c1f7
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=134ed7a0580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16630254580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0f1f7744db24/disk-48a5eed9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0abefd13fceb/vmlinux-48a5eed9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a1858ec33bb8/bzImage-48a5eed9.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/f81e1c2bd91c/mount_2.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+79e4e34c2a37d5a9c1f7@xxxxxxxxxxxxxxxxxxxxxxxxx

bcachefs (loop0): check_allocations... done
bcachefs (loop0): going read-write
bcachefs (loop0): done starting filesystem
=====================================================
BUG: KMSAN: uninit-value in variable__ffs arch/x86/include/asm/bitops.h:251 [inline]
BUG: KMSAN: uninit-value in extent_entry_type fs/bcachefs/extents.h:59 [inline]
BUG: KMSAN: uninit-value in extent_entry_bytes fs/bcachefs/extents.h:68 [inline]
BUG: KMSAN: uninit-value in extent_entry_u64s fs/bcachefs/extents.h:81 [inline]
BUG: KMSAN: uninit-value in bch2_extent_crc_append+0x7c2/0x830 fs/bcachefs/extents.c:593
variable__ffs arch/x86/include/asm/bitops.h:251 [inline]
extent_entry_type fs/bcachefs/extents.h:59 [inline]
extent_entry_bytes fs/bcachefs/extents.h:68 [inline]
extent_entry_u64s fs/bcachefs/extents.h:81 [inline]
bch2_extent_crc_append+0x7c2/0x830 fs/bcachefs/extents.c:593
init_append_extent+0x466/0x1050 fs/bcachefs/io_write.c:729
bch2_write_extent fs/bcachefs/io_write.c:1073 [inline]
__bch2_write+0x54a9/0x8490 fs/bcachefs/io_write.c:1487
bch2_write+0xc98/0x1af0 fs/bcachefs/io_write.c:1659
closure_queue include/linux/closure.h:270 [inline]
closure_call include/linux/closure.h:432 [inline]
bch2_writepage_do_io fs/bcachefs/fs-io-buffered.c:469 [inline]
bch2_writepages+0x24a/0x3c0 fs/bcachefs/fs-io-buffered.c:652
do_writepages+0x427/0xc30 mm/page-writeback.c:2687
filemap_fdatawrite_wbc mm/filemap.c:389 [inline]
__filemap_fdatawrite_range mm/filemap.c:422 [inline]
file_write_and_wait_range+0x6f2/0x7b0 mm/filemap.c:797
bch2_fsync+0xb6/0x510 fs/bcachefs/fs-io.c:228
vfs_fsync_range+0x1f9/0x260 fs/sync.c:187
generic_write_sync include/linux/fs.h:2970 [inline]
bch2_write_iter+0x4dce/0x50f0 fs/bcachefs/fs-io-buffered.c:1072
new_sync_write fs/read_write.c:586 [inline]
vfs_write+0xb34/0x1540 fs/read_write.c:679
ksys_write+0x240/0x4b0 fs/read_write.c:731
__do_sys_write fs/read_write.c:742 [inline]
__se_sys_write fs/read_write.c:739 [inline]
__x64_sys_write+0x93/0xe0 fs/read_write.c:739
x64_sys_call+0x3161/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:2
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 stored to memory at:
bch2_extent_crc_pack+0x686/0x6b0 fs/bcachefs/extents.c:549
bch2_extent_crc_append+0x645/0x830 fs/bcachefs/extents.c:591
init_append_extent+0x466/0x1050 fs/bcachefs/io_write.c:729
bch2_write_extent fs/bcachefs/io_write.c:1073 [inline]
__bch2_write+0x54a9/0x8490 fs/bcachefs/io_write.c:1487
bch2_write+0xc98/0x1af0 fs/bcachefs/io_write.c:1659
closure_queue include/linux/closure.h:270 [inline]
closure_call include/linux/closure.h:432 [inline]
bch2_writepage_do_io fs/bcachefs/fs-io-buffered.c:469 [inline]
bch2_writepages+0x24a/0x3c0 fs/bcachefs/fs-io-buffered.c:652
do_writepages+0x427/0xc30 mm/page-writeback.c:2687
filemap_fdatawrite_wbc mm/filemap.c:389 [inline]
__filemap_fdatawrite_range mm/filemap.c:422 [inline]
file_write_and_wait_range+0x6f2/0x7b0 mm/filemap.c:797
bch2_fsync+0xb6/0x510 fs/bcachefs/fs-io.c:228
vfs_fsync_range+0x1f9/0x260 fs/sync.c:187
generic_write_sync include/linux/fs.h:2970 [inline]
bch2_write_iter+0x4dce/0x50f0 fs/bcachefs/fs-io-buffered.c:1072
new_sync_write fs/read_write.c:586 [inline]
vfs_write+0xb34/0x1540 fs/read_write.c:679
ksys_write+0x240/0x4b0 fs/read_write.c:731
__do_sys_write fs/read_write.c:742 [inline]
__se_sys_write fs/read_write.c:739 [inline]
__x64_sys_write+0x93/0xe0 fs/read_write.c:739
x64_sys_call+0x3161/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:2
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:
__alloc_frozen_pages_noprof+0x9a7/0xe00 mm/page_alloc.c:4762
alloc_pages_mpol+0x4cd/0x890 mm/mempolicy.c:2270
alloc_frozen_pages_noprof+0x1bf/0x1e0 mm/mempolicy.c:2341
alloc_slab_page mm/slub.c:2423 [inline]
allocate_slab+0x23a/0x1110 mm/slub.c:2587
new_slab mm/slub.c:2640 [inline]
___slab_alloc+0x1287/0x3540 mm/slub.c:3826
__slab_alloc mm/slub.c:3916 [inline]
__slab_alloc_node mm/slub.c:3991 [inline]
slab_alloc_node mm/slub.c:4152 [inline]
kmem_cache_alloc_noprof+0x84e/0xe10 mm/slub.c:4171
mempool_alloc_slab+0x36/0x50 mm/mempool.c:559
mempool_init_node+0x202/0x4d0 mm/mempool.c:217
mempool_init_noprof+0x57/0x70 mm/mempool.c:246
bioset_init+0x279/0xb30 block/bio.c:1707
bch2_fs_fs_io_buffered_init+0x4a/0xc0 fs/bcachefs/fs-io-buffered.c:1084
bch2_fs_alloc fs/bcachefs/super.c:934 [inline]
bch2_fs_open+0x5654/0x5ba0 fs/bcachefs/super.c:2064
bch2_fs_get_tree+0x98a/0x24e0 fs/bcachefs/fs.c:2190
vfs_get_tree+0xb1/0x5a0 fs/super.c:1814
do_new_mount+0x71f/0x15e0 fs/namespace.c:3560
path_mount+0x742/0x1f10 fs/namespace.c:3887
do_mount fs/namespace.c:3900 [inline]
__do_sys_mount fs/namespace.c:4111 [inline]
__se_sys_mount+0x71f/0x800 fs/namespace.c:4088
__x64_sys_mount+0xe4/0x150 fs/namespace.c:4088
x64_sys_call+0x39bf/0x3c30 arch/x86/include/generated/asm/syscalls_64.h:166
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: 5782 Comm: syz-executor407 Not tainted 6.14.0-rc5-syzkaller-00016-g48a5eed9ad58 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
=====================================================

---
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Next message: Saurabh Singh Sengar: "Re: [PATCH 1/1] Drivers: hv: vmbus: Don't release fb_mmio resource in vmbus_free_mmio()"
Previous message: Michael Kelley: "RE: [PATCH 1/1] fbdev: hyperv_fb: Fix hang in kdump kernel when on Hyper-V Gen 2 VMs"
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