From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oo1-f80.google.com (mail-oo1-f80.google.com [209.85.161.80]) (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 8BE5E32D0D4 for ; Fri, 29 May 2026 21:34:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.161.80 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780090463; cv=none; b=lwyJiVEQudhv+JGFRrFx2iUE1K3fzDXqjDjhTrg7jmRFfY+HNA18whSfSQU5ztbgyT5xKzkUfJux11HiKppbxhidTvJogqHUaDK5PPbrpitn6NWoWQSj5nyELlys7PXJ1gLHkTbfqM1EC9ZlGBSb+Ls6zHKUBpMi/2OeEV835us= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780090463; c=relaxed/simple; bh=Yv6HaMsvX8OWpLQa5+Y2ygx/cOlhTf5VSP8dXoErOM0=; h=MIME-Version:Date:Message-ID:Subject:From:To:Content-Type; b=OKt33r1XzHbLPqjvJINSmEvt6xOsHaAPtq98AoIzqepb/k3ehHFSX4DCWwHxHaw0x3GppgeLgQCCTDP4/haQJryW7Efu8qh2WubtN5+CAVO6yxvdDdO88vKuAUgoWI11wHWoQfnPgWcLCKuk7hxx4tTpf8fhZS6nLOVdUAtgvsI= 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=209.85.161.80 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-oo1-f80.google.com with SMTP id 006d021491bc7-69e0b32a9ffso946201eaf.3 for ; Fri, 29 May 2026 14:34:22 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1780090461; x=1780695261; h=to:from:subject:message-id:date:mime-version:x-gm-message-state :from:to:cc:subject:date:message-id:reply-to; bh=B6aPnpvyAVuQFC8Pl1asar8RzwoQlcJgQai84S0/104=; b=JYAvGCalfjvKmszxdlvcUvvEPPVMAT84oWWS3Hfhcz76FVZ2LD0mNkKpeH4fHaDNFb Aip/gzhE5bQzExt9Oz3fSS1lPv1QHrdQkrpFLItm++tY+287WGKN8q5Cb1OVAgdmcWLH 3J7wxCGkh6DhprRh2IrGOQh/zIwP0RuPumnzhu5IBSdlEE/l/Pk9JRCqJGMHxZU7gPbA V0uJj1S1qvBzL5h8iXD3yfOZACktxLiLxiFRUxijHteRh0EaUYT2pNIJHVThdU26j78k AzRBTyPtYVW5nvFCQ8Pxv4ISKiVOxLAsxzXvatnejrvresbwO1597RhBz5qDXKG2dAeP pAqQ== X-Forwarded-Encrypted: i=1; AFNElJ/Jzz2rx/IoxVyJ7CjmBfV46iKloSVFGTV5fEYI3ij2WSM76JAL/2CejklRfQ96QcU5QrjLxDYMpGTwxS0=@vger.kernel.org X-Gm-Message-State: AOJu0YwXb+tVF1B4i37PTfb1TCiuLpDZ6xCoE6qxaGHjSJkNZ1aVxD+Y x6w9vLNh/Pf05FOifqGBp/FkHSCxe/fpH6pR5SBDW/V6h2RmU0TzSI8fiqjBKC46YdpRVDdTWna p34vDyLpbgUKgsM1bbmS5CQn5wiDrZlDsFdimNRwVCziUpVIV9BKzoaP+eUY= Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Received: by 2002:a05:6820:6ac2:b0:69d:eccd:e5a7 with SMTP id 006d021491bc7-69e10403fc5mr507800eaf.1.1780090461483; Fri, 29 May 2026 14:34:21 -0700 (PDT) Date: Fri, 29 May 2026 14:34:21 -0700 X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <6a1a065d.ba3b1513.1890b4.0004.GAE@google.com> Subject: [syzbot] [mm?] KCSAN: data-race in _copy_to_iter / _copy_to_iter (2) From: syzbot To: akpm@linux-foundation.org, baolin.wang@linux.alibaba.com, hughd@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, syzkaller-bugs@googlegroups.com Content-Type: text/plain; charset="UTF-8" Hello, syzbot found the following issue on: HEAD commit: d60ec36cab33 Merge tag 'mm-hotfixes-stable-2026-05-25-16-2.. git tree: upstream console output: https://syzkaller.appspot.com/x/log.txt?x=142ce056580000 kernel config: https://syzkaller.appspot.com/x/.config?x=d830408e2d151f21 dashboard link: https://syzkaller.appspot.com/bug?extid=3058ff8dcc2e370c7572 compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 Unfortunately, I don't have any reproducer for this issue yet. Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/bc5554f13e6c/disk-d60ec36c.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/d0317a873b98/vmlinux-d60ec36c.xz kernel image: https://storage.googleapis.com/syzbot-assets/6ceafe75f601/bzImage-d60ec36c.xz IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+3058ff8dcc2e370c7572@syzkaller.appspotmail.com ================================================================== BUG: KCSAN: data-race in _copy_to_iter / _copy_to_iter write to 0xffff888131894000 of 1024 bytes by task 49 on cpu 1: memcpy_to_iter lib/iov_iter.c:77 [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_to_iter+0x602/0xea0 lib/iov_iter.c:197 copy_page_to_iter+0x178/0x210 lib/iov_iter.c:374 copy_folio_to_iter include/linux/uio.h:204 [inline] shmem_file_read_iter+0x29e/0x4b0 mm/shmem.c:3426 lo_rw_aio+0x67d/0x730 drivers/block/loop.c:-1 do_req_filebacked drivers/block/loop.c:-1 [inline] loop_handle_cmd drivers/block/loop.c:1925 [inline] loop_process_work+0x56c/0xac0 drivers/block/loop.c:1960 loop_workfn+0x31/0x40 drivers/block/loop.c:1984 process_one_work kernel/workqueue.c:3314 [inline] process_scheduled_works+0x4f0/0x9c0 kernel/workqueue.c:3397 worker_thread+0x58a/0x780 kernel/workqueue.c:3478 kthread+0x22a/0x280 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 read to 0xffff888131894000 of 512 bytes by task 3290 on cpu 0: instrument_copy_to_user include/linux/instrumented.h:130 [inline] copy_to_user_iter lib/iov_iter.c:24 [inline] iterate_ubuf include/linux/iov_iter.h:30 [inline] iterate_and_advance2 include/linux/iov_iter.h:302 [inline] iterate_and_advance include/linux/iov_iter.h:330 [inline] _copy_to_iter+0x130/0xea0 lib/iov_iter.c:197 copy_page_to_iter+0x178/0x210 lib/iov_iter.c:374 copy_folio_to_iter include/linux/uio.h:204 [inline] filemap_read+0x407/0xa10 mm/filemap.c:2857 blkdev_read_iter+0x22d/0x2e0 block/fops.c:855 new_sync_read fs/read_write.c:493 [inline] vfs_read+0x6c0/0x7f0 fs/read_write.c:574 ksys_read+0xdc/0x1a0 fs/read_write.c:717 __do_sys_read fs/read_write.c:726 [inline] __se_sys_read fs/read_write.c:724 [inline] __x64_sys_read+0x40/0x50 fs/read_write.c:724 x64_sys_call+0x2886/0x3020 arch/x86/include/generated/asm/syscalls_64.h:1 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f Reported by Kernel Concurrency Sanitizer on: CPU: 0 UID: 0 PID: 3290 Comm: udevd Not tainted syzkaller #0 PREEMPT(full) Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026 ================================================================== --- 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