From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f208.google.com (mail-oi1-f208.google.com [209.85.167.208]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0E3EB3368B6 for ; Sun, 16 Aug 2026 06:46:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.208 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786862785; cv=none; b=dlIh6/Erk/PC6gRaSKmwKR5SwWbRlKfjKA8XOXMvKcFIlwuJITzyHSqKBZzTMFQ11LGttAe3GD8a+sEI4KpuaxNdx/gjp/yeWLyNGAu6k5In3AJ4iiRN0r/q3W3BmnxbK3qyYoAAh44p4DAaO9L+rVdlxqQ7n/p14MNXeJxZcqM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786862785; c=relaxed/simple; bh=cBDHEsWTeBXksJ9c9vlKC2mJbZdiQ2DN9v4xr3gB+Iw=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=u2dyaRZAXEDGtiqBSfRrPkurEr5lQ0ofUjndRqC+jA525PW5j4MnS9OAL3gR3UhT2c6ojv8WjYQpGuDYO753rufbbkYBB85pxfuox+sQaYYRh4d93RKksNQxBK3qlKQBQVv5SUUv4hod18YUKED9D8zdDqU8SBrE2t6MbbwaudU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com; arc=none smtp.client-ip=209.85.167.208 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=syzkaller.appspotmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=M3KW2WVRGUFZ5GODRSRYTGD7.apphosting.bounces.google.com Received: by mail-oi1-f208.google.com with SMTP id 5614622812f47-4b1bd8320ecso3813662b6e.3 for ; Sat, 15 Aug 2026 23:46:23 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1786862783; x=1787467583; h=content-type:to:from:subject:message-id:date:mime-version :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=xV4687rTqE9lsdbqyMEI9ZU2c9fh9f4443PgN01nqtg=; b=tPthsWv4UGz2K0SEy27djVbsHryhyAIdOYcVyTs20TR1KB6L4iUvUw/OTlnRtmU2Mo L3+DQRRau95qJyXXa1Kj8bD3EPPSTw3v9rEAYvJoHXqpua52IuPqE0mvqXx4vs1Zo2hQ N8C433//gYw2Yl932RtolErcpzckn6GAIrUvvpyyYWs+q4yv7kxakZpAE7yIWPXqrNzL 8eod7SvI5qG/waMJwoqpRMt96VmQZa8Uupi3LwizOdemyG0lU2OpHytwcdM5Jp1P1kii loZGm2hXOXBtZ3HGJVGLmb1EJt7nQMOYGMfBpENtm8pFaOqtrIwgLHKFX7DbY48GANF9 KCfQ== X-Forwarded-Encrypted: i=1; AHgh+Rq3tb1f7B1aGLO3MEP96lTNWna0fsMuAIHf/LZPcIr8oTUZEyri9W9EGgGj2ilNTu3vrr/EPD1Kb4jQWpQ=@vger.kernel.org X-Gm-Message-State: AOJu0YwB+HsJKjixbCEBABes9IIajGVHxi38dUkT3XmS8uEFR+tpqnFm Fn86t6woXJQngI3ZUnC50hkuBwiRRxVbOfV+zvKRqT0w6/sLFauE0K/xGr7eDGViG+ajCKRv4e0 KRRS/QKPCfdwr/x9+1on2x8AgI3+h2+VTtcsah+fShASDNughA8DukLjVzMs= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6808:f0d:b0:497:da7f:179a with SMTP id 5614622812f47-4b241f43193mr15366086b6e.21.1786862783012; Sat, 15 Aug 2026 23:46:23 -0700 (PDT) Date: Sat, 15 Aug 2026 23:46:22 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a815cbe.f7a79266.2f965f.000e.GAE@google.com> Subject: [syzbot] [exfat?] KCSAN: data-race in copy_folio_from_iter_atomic / fat_add_entries From: syzbot To: hirofumi@mail.parknet.co.jp, linkinjeon@kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, sj1557.seo@samsung.com, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: 3eb40771c00a Merge tag 'soc-fixes-7.2-3' of git://git.kern.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=108a9a79580000 kernel config: https://syzkaller.appspot.com/x/.config?x=e71a508528491732 dashboard link: https://syzkaller.appspot.com/bug?extid=f72da8b30ddc89cc2371 compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/b72e40f7d2c6/disk-3eb40771.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/19423dd4d544/vmlinux-3eb40771.xz kernel image: https://storage.googleapis.com/syzbot-assets/08b66d3a6723/bzImage-3eb40771.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+f72da8b30ddc89cc2371@syzkaller.appspotmail.com ================================================================== BUG: KCSAN: data-race in copy_folio_from_iter_atomic / fat_add_entries write to 0xffff8881090508c0 of 32 bytes by task 4733 on cpu 1: fat_add_entries+0x7d8/0x11c0 fs/fat/dir.c:1409 msdos_add_entry+0x1a2/0x270 fs/fat/namei_msdos.c:250 msdos_create+0x205/0x350 fs/fat/namei_msdos.c:289 lookup_open fs/namei.c:4508 [inline] open_last_lookups fs/namei.c:4608 [inline] path_openat+0xcfb/0x2000 fs/namei.c:4860 do_file_open+0x16c/0x290 fs/namei.c:4892 do_sys_openat2+0xa0/0x130 fs/open.c:1368 do_sys_open fs/open.c:1374 [inline] __do_sys_openat fs/open.c:1390 [inline] __se_sys_openat fs/open.c:1385 [inline] __x64_sys_openat+0xf2/0x120 fs/open.c:1385 x64_sys_call+0x1e39/0x3020 arch/x86/include/generated/asm/syscalls_64.h:258 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f read to 0xffff888109050800 of 2048 bytes by task 40 on cpu 0: memcpy_from_iter lib/iov_iter.c:85 [inline] iterate_bvec include/linux/iov_iter.h:123 [inline] iterate_and_advance2 include/linux/iov_iter.h:306 [inline] iterate_and_advance include/linux/iov_iter.h:330 [inline] __copy_from_iter lib/iov_iter.c:261 [inline] copy_folio_from_iter_atomic+0x728/0x10a0 lib/iov_iter.c:491 generic_perform_write+0x2c4/0x490 mm/filemap.c:4382 shmem_file_write_iter+0xc5/0xf0 mm/shmem.c:3424 lo_rw_aio+0x6a9/0x760 drivers/block/loop.c:-1 do_req_filebacked drivers/block/loop.c:-1 [inline] loop_handle_cmd drivers/block/loop.c:1917 [inline] loop_process_work+0x567/0xac0 drivers/block/loop.c:1952 loop_workfn+0x31/0x40 drivers/block/loop.c:1976 process_one_work kernel/workqueue.c:3322 [inline] process_scheduled_works+0x4d4/0x9a0 kernel/workqueue.c:3405 worker_thread+0x569/0x750 kernel/workqueue.c:3486 kthread+0x221/0x270 kernel/kthread.c:436 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 Reported by Kernel Concurrency Sanitizer on: CPU: 0 UID: 0 PID: 40 Comm: kworker/u8:2 Not tainted syzkaller #0 PREEMPT(lazy) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026 Workqueue: loop4 loop_workfn ================================================================== --- This report is generated by a bot. It may contain errors. See https://goo.gl/tpsmEJ for more information about syzbot. syzbot engineers can be reached at syzkaller@googlegroups.com. syzbot will keep track of this issue. See: https://goo.gl/tpsmEJ#status for how to communicate with syzbot. If the report is already addressed, let syzbot know by replying with: #syz fix: exact-commit-title If you want to overwrite report's subsystems, reply with: #syz set subsystems: new-subsystem (See the list of subsystem names on the web dashboard) If the report is a duplicate of another one, reply with: #syz dup: exact-subject-of-another-report If you want to undo deduplication, reply with: #syz undup