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Date: Sun, 04 Feb 2024 03:44:30 -0800
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Subject: Re: [syzbot] [btrfs?] KMSAN: uninit-value in bcmp (2)
From: syzbot <syzbot+3ce5dea5b1539ff36769@syzkaller.appspotmail.com>
To: amir73il@gmail.com, clm@fb.com, dsterba@suse.com, jack@suse.cz, 
	josef@toxicpanda.com, linux-btrfs@vger.kernel.org, 
	linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, 
	repnop@google.com, syzkaller-bugs@googlegroups.com
Content-Type: text/plain; charset="UTF-8"

syzbot has found a reproducer for the following issue on:

HEAD commit:    9f8413c4a66f Merge tag 'cgroup-for-6.8' of git://git.kerne..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=10fcfdc0180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=656820e61b758b15
dashboard link: https://syzkaller.appspot.com/bug?extid=3ce5dea5b1539ff36769
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=139dd53fe80000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=12685aa8180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/79d9f2f4b065/disk-9f8413c4.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cbc68430d9c6/vmlinux-9f8413c4.xz
kernel image: https://storage.googleapis.com/syzbot-assets/9740ad9fc172/bzImage-9f8413c4.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/25f4008bd752/mount_0.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3ce5dea5b1539ff36769@syzkaller.appspotmail.com

=====================================================
BUG: KMSAN: uninit-value in memcmp lib/string.c:692 [inline]
BUG: KMSAN: uninit-value in bcmp+0x186/0x1c0 lib/string.c:713
 memcmp lib/string.c:692 [inline]
 bcmp+0x186/0x1c0 lib/string.c:713
 fanotify_fh_equal fs/notify/fanotify/fanotify.c:51 [inline]
 fanotify_fid_event_equal fs/notify/fanotify/fanotify.c:72 [inline]
 fanotify_should_merge fs/notify/fanotify/fanotify.c:168 [inline]
 fanotify_merge+0x15f5/0x27e0 fs/notify/fanotify/fanotify.c:209
 fsnotify_insert_event+0x1d0/0x600 fs/notify/notification.c:113
 fanotify_handle_event+0x47f7/0x6140 fs/notify/fanotify/fanotify.c:966
 send_to_group fs/notify/fsnotify.c:360 [inline]
 fsnotify+0x2510/0x3530 fs/notify/fsnotify.c:570
 fsnotify_parent include/linux/fsnotify.h:80 [inline]
 fsnotify_file include/linux/fsnotify.h:100 [inline]
 fsnotify_close include/linux/fsnotify.h:362 [inline]
 __fput+0x578/0x10c0 fs/file_table.c:368
 __fput_sync+0x74/0x90 fs/file_table.c:467
 __do_sys_close fs/open.c:1554 [inline]
 __se_sys_close+0x28a/0x4c0 fs/open.c:1539
 __x64_sys_close+0x48/0x60 fs/open.c:1539
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

Uninit was created at:
 slab_post_alloc_hook+0x129/0xa70 mm/slab.h:768
 slab_alloc_node mm/slub.c:3478 [inline]
 slab_alloc mm/slub.c:3486 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3493 [inline]
 kmem_cache_alloc+0x579/0xa90 mm/slub.c:3502
 fanotify_alloc_fid_event fs/notify/fanotify/fanotify.c:584 [inline]
 fanotify_alloc_event fs/notify/fanotify/fanotify.c:817 [inline]
 fanotify_handle_event+0x2ff6/0x6140 fs/notify/fanotify/fanotify.c:952
 send_to_group fs/notify/fsnotify.c:360 [inline]
 fsnotify+0x2510/0x3530 fs/notify/fsnotify.c:570
 fsnotify_parent include/linux/fsnotify.h:80 [inline]
 fsnotify_file include/linux/fsnotify.h:100 [inline]
 fsnotify_close include/linux/fsnotify.h:362 [inline]
 __fput+0x578/0x10c0 fs/file_table.c:368
 __fput_sync+0x74/0x90 fs/file_table.c:467
 __do_sys_close fs/open.c:1554 [inline]
 __se_sys_close+0x28a/0x4c0 fs/open.c:1539
 __x64_sys_close+0x48/0x60 fs/open.c:1539
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x6d/0x140 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

CPU: 0 PID: 5010 Comm: syz-executor120 Not tainted 6.7.0-syzkaller-00562-g9f8413c4a66f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
=====================================================


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If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.