Re: [syzbot] [squashfs?] KMSAN: uninit-value in pick_link

[syzbot <syzbot+24ac24ff58dc5b0d26b9@syzkaller.appspotmail.com>]

Hello,

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

loop0: detected capacity change from 0 to 8
folio: ffffea0001163860, isize: -419430361, idx: 0, length: -419430361, squashfs_symlink_read_folio
error: 0, squashfs_symlink_read_folio
err: 0, folio: ffffea0001163860, folio uptod: 1, do_read_cache_folio
=====================================================
BUG: KMSAN: uninit-value in pick_link+0xd8c/0x1690 fs/namei.c:1850
 pick_link+0xd8c/0x1690 fs/namei.c:1850
 step_into+0x156f/0x1640 fs/namei.c:1909
 open_last_lookups fs/namei.c:3674 [inline]
 path_openat+0x39da/0x6100 fs/namei.c:3883
 do_filp_open+0x20e/0x590 fs/namei.c:3913
 do_sys_openat2+0x1bf/0x2f0 fs/open.c:1416
 do_sys_open fs/open.c:1431 [inline]
 __do_sys_openat fs/open.c:1447 [inline]
 __se_sys_openat fs/open.c:1442 [inline]
 __x64_sys_openat+0x2a1/0x310 fs/open.c:1442
 x64_sys_call+0x1fe/0x3c10 arch/x86/include/generated/asm/syscalls_64.h:258
 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_pages_noprof+0x9d6/0xe70 mm/page_alloc.c:4719
 alloc_pages_mpol_noprof+0x299/0x990 mm/mempolicy.c:2263
 alloc_pages_noprof mm/mempolicy.c:2343 [inline]
 folio_alloc_noprof+0x1db/0x310 mm/mempolicy.c:2350
 filemap_alloc_folio_noprof+0xa6/0x440 mm/filemap.c:1008
 do_read_cache_folio+0x121/0x10c0 mm/filemap.c:3753
 do_read_cache_page mm/filemap.c:3856 [inline]
 read_cache_page+0x63/0x1d0 mm/filemap.c:3865
 read_mapping_page include/linux/pagemap.h:907 [inline]
 page_get_link+0x73/0xab0 fs/namei.c:5272
 pick_link+0xd6c/0x1690
 step_into+0x156f/0x1640 fs/namei.c:1909
 open_last_lookups fs/namei.c:3674 [inline]
 path_openat+0x39da/0x6100 fs/namei.c:3883
 do_filp_open+0x20e/0x590 fs/namei.c:3913
 do_sys_openat2+0x1bf/0x2f0 fs/open.c:1416
 do_sys_open fs/open.c:1431 [inline]
 __do_sys_openat fs/open.c:1447 [inline]
 __se_sys_openat fs/open.c:1442 [inline]
 __x64_sys_openat+0x2a1/0x310 fs/open.c:1442
 x64_sys_call+0x1fe/0x3c10 arch/x86/include/generated/asm/syscalls_64.h:258
 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: 5977 Comm: syz.0.15 Not tainted 6.10.0-syzkaller-12708-g2f8c4f506285-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
=====================================================


Tested on:

commit:         2f8c4f50 Merge tag 'auxdisplay-for-v6.11-tag1' of git:..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=1192af45980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ea3a063e5f96c3d6
dashboard link: https://syzkaller.appspot.com/bug?extid=24ac24ff58dc5b0d26b9
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=137d83bd980000