In the Linux kernel, the following vulnerability has been resolved:

hfs: fix to initialize fields of hfs_inode_info after hfs_alloc_inode()

Syzbot reports uninitialized value access issue as below:

loop0: detected capacity change from 0 to 64

BUG: KMSAN: uninit-value in hfs_revalidate_dentry+0x307/0x3f0 fs/hfs/sysdep.c:30 hfs_revalidate_dentry+0x307/0x3f0 fs/hfs/sysdep.c:30 d_revalidate fs/namei.c:862 [inline] lookup_fast+0x89e/0x8e0 fs/namei.c:1649 walk_component fs/namei.c:2001 [inline] link_path_walk+0x817/0x1480 fs/namei.c:2332 path_lookupat+0xd9/0x6f0 fs/namei.c:2485 filename_lookup+0x22e/0x740 fs/namei.c:2515 user_path_at_empty+0x8b/0x390 fs/namei.c:2924 user_path_at include/linux/namei.h:57 [inline] do_mount fs/namespace.c:3689 [inline] __do_sys_mount fs/namespace.c:3898 [inline] __se_sys_mount+0x66b/0x810 fs/namespace.c:3875 __x64_sys_mount+0xe4/0x140 fs/namespace.c:3875 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x63/0x6b

BUG: KMSAN: uninit-value in hfs_ext_read_extent fs/hfs/extent.c:196 [inline] BUG: KMSAN: uninit-value in hfs_get_block+0x92d/0x1620 fs/hfs/extent.c:366 hfs_ext_read_extent fs/hfs/extent.c:196 [inline] hfs_get_block+0x92d/0x1620 fs/hfs/extent.c:366 block_read_full_folio+0x4ff/0x11b0 fs/buffer.c:2271 hfs_read_folio+0x55/0x60 fs/hfs/inode.c:39 filemap_read_folio+0x148/0x4f0 mm/filemap.c:2426 do_read_cache_folio+0x7c8/0xd90 mm/filemap.c:3553 do_read_cache_page mm/filemap.c:3595 [inline] read_cache_page+0xfb/0x2f0 mm/filemap.c:3604 read_mapping_page include/linux/pagemap.h:755 [inline] hfs_btree_open+0x928/0x1ae0 fs/hfs/btree.c:78 hfs_mdb_get+0x260c/0x3000 fs/hfs/mdb.c:204 hfs_fill_super+0x1fb1/0x2790 fs/hfs/super.c:406 mount_bdev+0x628/0x920 fs/super.c:1359 hfs_mount+0xcd/0xe0 fs/hfs/super.c:456 legacy_get_tree+0x167/0x2e0 fs/fs_context.c:610 vfs_get_tree+0xdc/0x5d0 fs/super.c:1489 do_new_mount+0x7a9/0x16f0 fs/namespace.c:3145 path_mount+0xf98/0x26a0 fs/namespace.c:3475 do_mount fs/namespace.c:3488 [inline] __do_sys_mount fs/namespace.c:3697 [inline] __se_sys_mount+0x919/0x9e0 fs/namespace.c:3674 __ia32_sys_mount+0x15b/0x1b0 fs/namespace.c:3674 do_syscall_32_irqs_on arch/x86/entry/common.c:112 [inline] __do_fast_syscall_32+0xa2/0x100 arch/x86/entry/common.c:178 do_fast_syscall_32+0x37/0x80 arch/x86/entry/common.c:203 do_SYSENTER_32+0x1f/0x30 arch/x86/entry/common.c:246 entry_SYSENTER_compat_after_hwframe+0x70/0x82

Uninit was created at: __alloc_pages+0x9a6/0xe00 mm/page_alloc.c:4590 __alloc_pages_node include/linux/gfp.h:238 [inline] alloc_pages_node include/linux/gfp.h:261 [inline] alloc_slab_page mm/slub.c:2190 [inline] allocate_slab mm/slub.c:2354 [inline] new_slab+0x2d7/0x1400 mm/slub.c:2407 ___slab_alloc+0x16b5/0x3970 mm/slub.c:3540 __slab_alloc mm/slub.c:3625 [inline] __slab_alloc_node mm/slub.c:3678 [inline] slab_alloc_node mm/slub.c:3850 [inline] kmem_cache_alloc_lru+0x64d/0xb30 mm/slub.c:3879 alloc_inode_sb include/linux/fs.h:3018 [inline] hfs_alloc_inode+0x5a/0xc0 fs/hfs/super.c:165 alloc_inode+0x83/0x440 fs/inode.c:260 new_inode_pseudo fs/inode.c:1005 [inline] new_inode+0x38/0x4f0 fs/inode.c:1031 hfs_new_inode+0x61/0x1010 fs/hfs/inode.c:186 hfs_mkdir+0x54/0x250 fs/hfs/dir.c:228 vfs_mkdir+0x49a/0x700 fs/namei.c:4126 do_mkdirat+0x529/0x810 fs/namei.c:4149 __do_sys_mkdirat fs/namei.c:4164 [inline] __se_sys_mkdirat fs/namei.c:4162 [inline] __x64_sys_mkdirat+0xc8/0x120 fs/namei.c:4162 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcf/0x1e0 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x63/0x6b

It missed to initialize .tz_secondswest, .cached_start and .cached_blocks fields in struct hfs_inode_info after hfs_alloc_inode(), fix it.

Weakness

The product uses or accesses a resource that has not been initialized.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/10f7163bfb5f8b4e0c9c05a939f20b8540e33c65
• https://git.kernel.org/stable/c/26a2ed107929a855155429b11e1293b83e6b2a8b
• https://git.kernel.org/stable/c/4a52861cd76e79f1a593beb23d096523eb9732c2
• https://git.kernel.org/stable/c/58d83fc160505a7009c39dec64effaac5129b971
• https://git.kernel.org/stable/c/9c4e40b9b731220f9464975e49da75496e3865c4
• https://git.kernel.org/stable/c/d3493d6f0dfb1ab5225b62faa77732983f2187a1
• https://git.kernel.org/stable/c/d55aae5c1730d6b70d5d8eaff00113cd34772ea3
• https://git.kernel.org/stable/c/f7316b2b2f11cf0c6de917beee8d3de728be24db
• https://lists.debian.org/debian-lts-announce/2024/10/msg00003.html
• https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html