[syzbot] [squashfs?] KMSAN: uninit-value in squashfs_get_parent

[syzbot <syzbot+157bdef5cf596ad0da2c@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    d4b779985a6c Merge tag 'for-6.17/dm-fixes' of git://git.ke..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11f35f62580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=1b093ccee5a9e08c
dashboard link: https://syzkaller.appspot.com/bug?extid=157bdef5cf596ad0da2c
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11eb8712580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=13f35f62580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/dfaa51c15f16/disk-d4b77998.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b0cba4bd6519/vmlinux-d4b77998.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6d7ca6f9de66/bzImage-d4b77998.xz
mounted in repro #1: https://storage.googleapis.com/syzbot-assets/adb7ed65b055/mount_4.gz
mounted in repro #2: https://storage.googleapis.com/syzbot-assets/93757edce8f3/mount_7.gz
  fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=10f9ef62580000)

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+157bdef5cf596ad0da2c@syzkaller.appspotmail.com

loop2: detected capacity change from 0 to 8
=====================================================
BUG: KMSAN: uninit-value in squashfs_inode_lookup fs/squashfs/export.c:50 [inline]
BUG: KMSAN: uninit-value in squashfs_export_iget fs/squashfs/export.c:74 [inline]
BUG: KMSAN: uninit-value in squashfs_get_parent+0x3e9/0x540 fs/squashfs/export.c:108
 squashfs_inode_lookup fs/squashfs/export.c:50 [inline]
 squashfs_export_iget fs/squashfs/export.c:74 [inline]
 squashfs_get_parent+0x3e9/0x540 fs/squashfs/export.c:108
 reconnect_one fs/exportfs/expfs.c:130 [inline]
 reconnect_path+0x305/0xd30 fs/exportfs/expfs.c:220
 exportfs_decode_fh_raw+0x8bf/0xef0 fs/exportfs/expfs.c:535
 do_handle_to_path+0xe5/0x310 fs/fhandle.c:270
 handle_to_path fs/fhandle.c:394 [inline]
 do_handle_open+0xcb4/0x1220 fs/fhandle.c:409
 __do_sys_open_by_handle_at fs/fhandle.c:449 [inline]
 __se_sys_open_by_handle_at fs/fhandle.c:440 [inline]
 __x64_sys_open_by_handle_at+0xa6/0x100 fs/fhandle.c:440
 x64_sys_call+0x2f60/0x3e20 arch/x86/include/generated/asm/syscalls_64.h:305
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Uninit was created at:
 __alloc_frozen_pages_noprof+0x689/0xf00 mm/page_alloc.c:5171
 alloc_pages_mpol+0x328/0x860 mm/mempolicy.c:2416
 alloc_frozen_pages_noprof+0xf7/0x200 mm/mempolicy.c:2487
 alloc_slab_page mm/slub.c:2492 [inline]
 allocate_slab+0x24d/0x1220 mm/slub.c:2660
 new_slab mm/slub.c:2714 [inline]
 ___slab_alloc+0xff3/0x3470 mm/slub.c:3901
 __slab_alloc mm/slub.c:3992 [inline]
 __slab_alloc_node mm/slub.c:4067 [inline]
 slab_alloc_node mm/slub.c:4228 [inline]
 kmem_cache_alloc_lru_noprof+0x922/0xed0 mm/slub.c:4259
 squashfs_alloc_inode+0x5a/0xd0 fs/squashfs/super.c:673
 alloc_inode+0x8a/0x4a0 fs/inode.c:346
 new_inode+0x39/0x460 fs/inode.c:1145
 squashfs_fill_super+0x218c/0x3670 fs/squashfs/super.c:339
 get_tree_bdev_flags+0x6e3/0x920 fs/super.c:1692
 get_tree_bdev+0x38/0x50 fs/super.c:1715
 squashfs_get_tree+0x35/0x40 fs/squashfs/super.c:493
 vfs_get_tree+0xb0/0x5c0 fs/super.c:1815
 do_new_mount+0x733/0x1420 fs/namespace.c:3808
 path_mount+0x6db/0x1e90 fs/namespace.c:4123
 do_mount fs/namespace.c:4136 [inline]
 __do_sys_mount fs/namespace.c:4347 [inline]
 __se_sys_mount+0x6eb/0x7d0 fs/namespace.c:4324
 __x64_sys_mount+0xe4/0x150 fs/namespace.c:4324
 x64_sys_call+0x3604/0x3e20 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd9/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 0 UID: 0 PID: 6220 Comm: syz.2.23 Not tainted syzkaller #0 PREEMPT(none) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
=====================================================


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