From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ot1-f78.google.com (mail-ot1-f78.google.com [209.85.210.78]) (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 6DD5A39E6FF for ; Thu, 16 Apr 2026 10:23:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.78 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776335013; cv=none; b=upzJF4zna6h1gr5rp+9jz2odk93UTY82dP/5uXUECSkJLAzITVYbxb7LGWF8ob1AHNAu3tZMfcSdeckn5tY1Y/RFY8uQZn3pgVjl3LBE/0hBzTNm9wY5gQ9AD9bHYtiu3s1pDDZF9KtniIzrf7l73fzP42fgo9lZces1NmNGgBQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776335013; c=relaxed/simple; bh=86rrRW0OeEjfz9g5De6WIdSIDA+rFEgesRYg8zJNz5k=; h=MIME-Version:Date:In-Reply-To:Message-ID:Subject:From:To: Content-Type; 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006d021491bc7-68eb6754550mr8852634eaf.30.1776335011373; Thu, 16 Apr 2026 03:23:31 -0700 (PDT) Date: Thu, 16 Apr 2026 03:23:31 -0700 In-Reply-To: <69ca48ca.050a0220.183828.001a.GAE@google.com> X-Google-Appengine-App-Id: s~syzkaller X-Google-Appengine-App-Id-Alias: syzkaller Message-ID: <69e0b8a3.a00a0220.8f24c.017a.GAE@google.com> Subject: Re: [syzbot] [mm?] KASAN: use-after-free Read in copy_folio_from_iter_atomic (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, tahernady45@gmail.com Content-Type: text/plain; charset="UTF-8" syzbot has found a reproducer for the following issue on: HEAD commit: e6efabc0afca Add linux-next specific files for 20260414 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=17908702580000 kernel config: https://syzkaller.appspot.com/x/.config?x=56c2b36de3316f1b dashboard link: https://syzkaller.appspot.com/bug?extid=6cc93ec9a4035badb85f compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8 syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14c798ce580000 C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1142c4ce580000 Downloadable assets: disk image: https://storage.googleapis.com/syzbot-assets/e7099cbf73e4/disk-e6efabc0.raw.xz vmlinux: https://storage.googleapis.com/syzbot-assets/439c402df1b9/vmlinux-e6efabc0.xz kernel image: https://storage.googleapis.com/syzbot-assets/fc0c0175fc76/bzImage-e6efabc0.xz mounted in repro: https://storage.googleapis.com/syzbot-assets/94fa7bad6be9/mount_0.gz fsck result: failed (log: https://syzkaller.appspot.com/x/fsck.log?x=17017b16580000) IMPORTANT: if you fix the issue, please add the following tag to the commit: Reported-by: syzbot+6cc93ec9a4035badb85f@syzkaller.appspotmail.com ================================================================== BUG: KASAN: use-after-free in memcpy_from_iter lib/iov_iter.c:85 [inline] BUG: KASAN: use-after-free in iterate_bvec include/linux/iov_iter.h:123 [inline] BUG: KASAN: use-after-free in iterate_and_advance2 include/linux/iov_iter.h:306 [inline] BUG: KASAN: use-after-free in iterate_and_advance include/linux/iov_iter.h:330 [inline] BUG: KASAN: use-after-free in __copy_from_iter lib/iov_iter.c:261 [inline] BUG: KASAN: use-after-free in copy_folio_from_iter_atomic+0xbb5/0x1ad0 lib/iov_iter.c:491 Read of size 4096 at addr ffff888037cb3000 by task kworker/u8:7/1020 CPU: 0 UID: 0 PID: 1020 Comm: kworker/u8:7 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026 Workqueue: loop0 loop_workfn Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description+0x55/0x1e0 mm/kasan/report.c:378 print_report+0x58/0x70 mm/kasan/report.c:482 kasan_report+0x117/0x150 mm/kasan/report.c:595 check_region_inline mm/kasan/generic.c:-1 [inline] kasan_check_range+0x264/0x2c0 mm/kasan/generic.c:200 __asan_memcpy+0x29/0x70 mm/kasan/shadow.c:105 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+0xbb5/0x1ad0 lib/iov_iter.c:491 generic_perform_write+0x5b1/0x8b0 mm/filemap.c:4342 shmem_file_write_iter+0xfb/0x120 mm/shmem.c:3478 lo_rw_aio+0xc80/0xf00 include/linux/percpu-rwsem.h:-1 do_req_filebacked drivers/block/loop.c:433 [inline] loop_handle_cmd drivers/block/loop.c:1925 [inline] loop_process_work+0x637/0x11b0 drivers/block/loop.c:1960 process_one_work kernel/workqueue.c:3308 [inline] process_scheduled_works+0xb68/0x1910 kernel/workqueue.c:3399 worker_thread+0xa90/0x1040 kernel/workqueue.c:3485 kthread+0x388/0x470 kernel/kthread.c:436 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x38 pfn:0x37cb3 flags: 0x80000000000000(node=0|zone=1) raw: 0080000000000000 ffffea0000d17548 ffffea0001353448 0000000000000000 raw: 0000000000000038 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected page_owner tracks the page as freed page last allocated via order 0, migratetype Unmovable, gfp_mask 0xdc0(GFP_KERNEL|__GFP_ZERO), pid 6098, tgid 6098 (syz.0.91), ts 154383709391, free_ts 154428922615 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x231/0x280 mm/page_alloc.c:1858 prep_new_page mm/page_alloc.c:1866 [inline] get_page_from_freelist+0x27d6/0x2850 mm/page_alloc.c:3946 __alloc_frozen_pages_noprof+0x18d/0x380 mm/page_alloc.c:5226 alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2490 alloc_frozen_pages_noprof mm/mempolicy.c:2561 [inline] alloc_pages_noprof+0xd2/0x2f0 mm/mempolicy.c:2581 lbmLogInit fs/jfs/jfs_logmgr.c:1813 [inline] lmLogInit+0x357/0x1a00 fs/jfs/jfs_logmgr.c:1267 open_inline_log fs/jfs/jfs_logmgr.c:1173 [inline] lmLogOpen+0x4e1/0xfa0 fs/jfs/jfs_logmgr.c:1067 jfs_mount_rw+0xee/0x670 fs/jfs/jfs_mount.c:257 jfs_fill_super+0x754/0xd80 fs/jfs/super.c:532 get_tree_bdev_flags+0x431/0x4f0 fs/super.c:1694 vfs_get_tree+0x92/0x2a0 fs/super.c:1754 fc_mount fs/namespace.c:1193 [inline] do_new_mount_fc fs/namespace.c:3758 [inline] do_new_mount+0x341/0xd30 fs/namespace.c:3834 do_mount fs/namespace.c:4167 [inline] __do_sys_mount fs/namespace.c:4399 [inline] __se_sys_mount+0x31d/0x420 fs/namespace.c:4376 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0x15f/0xf80 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f page last free pid 5945 tgid 5945 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] __free_pages_prepare mm/page_alloc.c:1402 [inline] __free_frozen_pages+0xf9b/0x10f0 mm/page_alloc.c:2943 lbmLogShutdown fs/jfs/jfs_logmgr.c:1861 [inline] lmLogShutdown+0x44e/0x850 fs/jfs/jfs_logmgr.c:1681 lmLogClose+0x28a/0x520 fs/jfs/jfs_logmgr.c:1457 jfs_umount+0x2fb/0x3d0 fs/jfs/jfs_umount.c:124 jfs_put_super+0x8c/0x190 fs/jfs/super.c:194 generic_shutdown_super+0x13d/0x2d0 fs/super.c:646 kill_block_super+0x44/0x90 fs/super.c:1725 deactivate_locked_super+0xbc/0x130 fs/super.c:476 cleanup_mnt+0x437/0x4d0 fs/namespace.c:1312 task_work_run+0x1d9/0x270 kernel/task_work.c:233 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] __exit_to_user_mode_loop kernel/entry/common.c:67 [inline] exit_to_user_mode_loop+0xed/0x480 kernel/entry/common.c:98 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline] syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:238 [inline] syscall_exit_to_user_mode include/linux/entry-common.h:328 [inline] do_syscall_64+0x33e/0xf80 arch/x86/entry/syscall_64.c:100 entry_SYSCALL_64_after_hwframe+0x77/0x7f Memory state around the buggy address: ffff888037cb2f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff888037cb2f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff888037cb3000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ^ ffff888037cb3080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ffff888037cb3100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ================================================================== --- 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.