From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it1-f199.google.com ([209.85.166.199]:51193 "EHLO mail-it1-f199.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730845AbeKGObt (ORCPT ); Wed, 7 Nov 2018 09:31:49 -0500 Received: by mail-it1-f199.google.com with SMTP id p206-v6so13947355itc.0 for ; Tue, 06 Nov 2018 21:03:05 -0800 (PST) MIME-Version: 1.0 Date: Tue, 06 Nov 2018 21:03:04 -0800 Message-ID: <0000000000008628be057a0c089f@google.com> Subject: KASAN: use-after-free Read in locks_remove_flock From: syzbot To: bfields@fieldses.org, jlayton@kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk Content-Type: text/plain; charset="UTF-8"; format=flowed; delsp=yes Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Hello, syzbot found the following crash on: HEAD commit: d881de30d29e Add linux-next specific files for 20181107 git tree: linux-next console output: https://syzkaller.appspot.com/x/log.txt?x=16e42f5b400000 kernel config: https://syzkaller.appspot.com/x/.config?x=caa433e1c8778437 dashboard link: https://syzkaller.appspot.com/bug?extid=34a98afb89842107f03f compiler: gcc (GCC) 8.0.1 20180413 (experimental) Unfortunately, I don't have any reproducer for this crash yet. IMPORTANT: if you fix the bug, please add the following tag to the commit: Reported-by: syzbot+34a98afb89842107f03f@syzkaller.appspotmail.com ================================================================== BUG: KASAN: use-after-free in locks_remove_flock+0x33c/0x350 fs/locks.c:2567 Read of size 8 at addr ffff8801c92fc040 by task syz-executor1/15515 CPU: 1 PID: 15515 Comm: syz-executor1 Not tainted 4.20.0-rc1-next-20181107+ #107 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x244/0x39d lib/dump_stack.c:113 print_address_description.cold.7+0x9/0x1ff mm/kasan/report.c:256 kasan_report_error mm/kasan/report.c:354 [inline] kasan_report.cold.8+0x242/0x309 mm/kasan/report.c:412 __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 locks_remove_flock+0x33c/0x350 fs/locks.c:2567 locks_remove_file+0x148/0x5c0 fs/locks.c:2607 __fput+0x2f0/0xa70 fs/file_table.c:271 ____fput+0x15/0x20 fs/file_table.c:312 task_work_run+0x1e8/0x2a0 kernel/task_work.c:113 tracehook_notify_resume include/linux/tracehook.h:188 [inline] exit_to_usermode_loop+0x318/0x380 arch/x86/entry/common.c:166 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline] syscall_return_slowpath arch/x86/entry/common.c:268 [inline] do_syscall_64+0x6be/0x820 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x457569 Code: fd b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 cb b3 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007fc1e8ed4c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000049 RAX: 0000000000000000 RBX: 0000000000000002 RCX: 0000000000457569 RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000003 RBP: 000000000072bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007fc1e8ed56d4 R13: 00000000004bdd9e R14: 00000000004ccdb8 R15: 00000000ffffffff Allocated by task 15515: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] kasan_kmalloc+0xc7/0xe0 mm/kasan/kasan.c:553 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490 kmem_cache_alloc+0x12e/0x730 mm/slab.c:3554 kmem_cache_zalloc include/linux/slab.h:731 [inline] locks_alloc_lock+0x9e/0x300 fs/locks.c:304 flock_make_lock+0x22c/0x2a0 fs/locks.c:438 __do_sys_flock fs/locks.c:2057 [inline] __se_sys_flock fs/locks.c:2038 [inline] __x64_sys_flock+0x12b/0x350 fs/locks.c:2038 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe Freed by task 15515: save_stack+0x43/0xd0 mm/kasan/kasan.c:448 set_track mm/kasan/kasan.c:460 [inline] __kasan_slab_free+0x102/0x150 mm/kasan/kasan.c:521 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 __cache_free mm/slab.c:3498 [inline] kmem_cache_free+0x83/0x290 mm/slab.c:3760 locks_free_lock+0x295/0x420 fs/locks.c:341 __do_sys_flock fs/locks.c:2078 [inline] __se_sys_flock fs/locks.c:2038 [inline] __x64_sys_flock+0x289/0x350 fs/locks.c:2038 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe The buggy address belongs to the object at ffff8801c92fc000 which belongs to the cache file_lock_cache of size 264 The buggy address is located 64 bytes inside of 264-byte region [ffff8801c92fc000, ffff8801c92fc108) The buggy address belongs to the page: page:ffffea000724bf00 count:1 mapcount:0 mapping:ffff8801d9a1c3c0 index:0x0 flags: 0x2fffc0000000200(slab) raw: 02fffc0000000200 ffff8801d9a82e48 ffffea00075e1608 ffff8801d9a1c3c0 raw: 0000000000000000 ffff8801c92fc000 000000010000000c 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8801c92fbf00: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc ffff8801c92fbf80: fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc fc > ffff8801c92fc000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8801c92fc080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8801c92fc100: fb fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb ================================================================== ------------[ cut here ]------------ downgrading a read lock WARNING: CPU: 0 PID: 15521 at kernel/locking/lockdep.c:3556 __lock_downgrade kernel/locking/lockdep.c:3556 [inline] WARNING: CPU: 0 PID: 15521 at kernel/locking/lockdep.c:3556 lock_downgrade+0x4d7/0x900 kernel/locking/lockdep.c:3819 --- This bug is generated by a bot. 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