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

syzbot
2024-07-31T08:12:28Z

Hello,

syzbot found the following issue on:

HEAD commit: 2f8c4f506285 Merge tag 'auxdisplay-for-v6.11-tag1' of git:..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=145d019d980000
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
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1629a655980000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16bfb899980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ed9f828b1910/disk-2f8c4f50.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b8bdff998eb1/vmlinux-2f8c4f50.xz
kernel image: https://storage.googleapis.com/syzbot-assets/41b7030717aa/bzImage-2f8c4f50.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/6b20d8f48921/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+24ac24ff58dc5b0d26b9@syzkaller.appspotmail.com

loop0: detected capacity change from 0 to 8
=====================================================
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+0x12a/0xfd0 mm/filemap.c:3753
do_read_cache_page mm/filemap.c:3855 [inline]
read_cache_page+0x63/0x1d0 mm/filemap.c:3864
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: 0 UID: 0 PID: 5191 Comm: syz-executor190 Not tainted 6.10.0-syzkaller-12708-g2f8c4f506285 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
=====================================================

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