linux-kernel - Re: [syzbot] [bcachefs?] KMSAN: uninit-value in bch2_extent_crc

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [day] [month] [year] [list]
Message-ID: <67e4faf9.050a0220.2f068f.0022.GAE@google.com>
Date: Thu, 27 Mar 2025 00:15:05 -0700
From: syzbot <syzbot+79e4e34c2a37d5a9c1f7@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org, richard120310@...il.com, 
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [bcachefs?] KMSAN: uninit-value in bch2_extent_crc_append
 (2)

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KMSAN: uninit-value in bch2_extent_crc_append

bcachefs (loop0): stripes_read... done
bcachefs (loop0): snapshots_read... done
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:388 [inline]
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 file_write_and_wait_range+0x6f2/0x7b0 mm/filemap.c:796
 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:388 [inline]
 __filemap_fdatawrite_range mm/filemap.c:421 [inline]
 file_write_and_wait_range+0x6f2/0x7b0 mm/filemap.c:796
 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:4763
 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:2065
 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: 1 UID: 0 PID: 6726 Comm: syz.0.16 Not tainted 6.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
=====================================================


Tested on:

commit:         38fec10e Linux 6.14
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=10036de4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=b250f29c9561410d
dashboard link: https://syzkaller.appspot.com/bug?extid=79e4e34c2a37d5a9c1f7
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.