Re: [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_delete_cat

[syzbot <syzbot+fdedff847a0e5e84c39f@syzkaller.appspotmail.com>]

syzbot has found a reproducer for the following issue on:

HEAD commit:    97e36f4aa06f Revert "sched/core: kmsan: do not instrument ..
git tree:       https://github.com/google/kmsan.git master
console output: https://syzkaller.appspot.com/x/log.txt?x=1776cd44c80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=46c642641b9ef616
dashboard link: https://syzkaller.appspot.com/bug?extid=fdedff847a0e5e84c39f
compiler:       Debian clang version 15.0.7, GNU ld (GNU Binutils for Debian) 2.35.2
userspace arch: i386
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1602e2acc80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=14c73260c80000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9931a9627dc6/disk-97e36f4a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1aafdb2fd6dc/vmlinux-97e36f4a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/90df5872c7ff/bzImage-97e36f4a.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/ad4aeec6ed10/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fdedff847a0e5e84c39f@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 1024
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BUG: KMSAN: uninit-value in hfsplus_lookup+0x679/0xf20 fs/hfsplus/dir.c:83
 hfsplus_lookup+0x679/0xf20 fs/hfsplus/dir.c:83
 __lookup_slow+0x528/0x730 fs/namei.c:1685
 lookup_slow+0x6a/0xc0 fs/namei.c:1702
 walk_component+0x462/0x650 fs/namei.c:1993
 lookup_last fs/namei.c:2450 [inline]
 path_lookupat+0x27d/0x6f0 fs/namei.c:2474
 filename_lookup+0x250/0x800 fs/namei.c:2503
 user_path_at_empty+0x87/0x3a0 fs/namei.c:2876
 user_path_at include/linux/namei.h:57 [inline]
 path_setxattr+0x82/0x3f0 fs/xattr.c:645
 __do_sys_lsetxattr fs/xattr.c:673 [inline]
 __se_sys_lsetxattr fs/xattr.c:669 [inline]
 __ia32_sys_lsetxattr+0xed/0x170 fs/xattr.c:669
 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+0x9f6/0xe90 mm/page_alloc.c:5572
 alloc_pages+0xab0/0xd80 mm/mempolicy.c:2287
 alloc_slab_page mm/slub.c:1851 [inline]
 allocate_slab mm/slub.c:1998 [inline]
 new_slab+0x425/0x15f0 mm/slub.c:2051
 ___slab_alloc+0x109c/0x32d0 mm/slub.c:3193
 __slab_alloc mm/slub.c:3292 [inline]
 __slab_alloc_node mm/slub.c:3345 [inline]
 slab_alloc_node mm/slub.c:3442 [inline]
 slab_alloc mm/slub.c:3460 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3467 [inline]
 kmem_cache_alloc_lru+0x5fb/0xa50 mm/slub.c:3483
 alloc_inode_sb include/linux/fs.h:3119 [inline]
 hfsplus_alloc_inode+0x5a/0xc0 fs/hfsplus/super.c:627
 alloc_inode+0x83/0x440 fs/inode.c:259
 iget_locked+0x2dd/0xe80 fs/inode.c:1286
 hfsplus_iget+0x63/0xb70 fs/hfsplus/super.c:64
 hfsplus_btree_open+0x13e/0x1d20 fs/hfsplus/btree.c:150
 hfsplus_fill_super+0x12bb/0x2a80 fs/hfsplus/super.c:473
 mount_bdev+0x50e/0x840 fs/super.c:1359
 hfsplus_mount+0x4d/0x60 fs/hfsplus/super.c:641
 legacy_get_tree+0x110/0x290 fs/fs_context.c:610
 vfs_get_tree+0xa5/0x500 fs/super.c:1489
 do_new_mount+0x69a/0x1580 fs/namespace.c:3145
 path_mount+0x725/0x1ec0 fs/namespace.c:3475
 do_mount fs/namespace.c:3488 [inline]
 __do_sys_mount fs/namespace.c:3697 [inline]
 __se_sys_mount+0x734/0x840 fs/namespace.c:3674
 __ia32_sys_mount+0xe3/0x150 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

CPU: 1 PID: 5005 Comm: syz-executor236 Not tainted 6.2.0-syzkaller-81152-g97e36f4aa06f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/16/2023
=====================================================