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[81.185.169.230]) by smtp.gmail.com with ESMTPSA id z13sm16904472wrw.36.2019.04.02.13.03.34 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 02 Apr 2019 13:03:35 -0700 (PDT) Subject: Re: KASAN: use-after-free Read in __dev_map_entry_free To: syzbot , ast@kernel.org, daniel@iogearbox.net, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, syzkaller-bugs@googlegroups.com References: <0000000000009cd09a056f1451d1@google.com> From: Eric Dumazet Message-ID: Date: Tue, 2 Apr 2019 13:03:30 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <0000000000009cd09a056f1451d1@google.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/20/2018 08:19 AM, syzbot wrote: > Hello, > > syzbot found the following crash on: > > HEAD commit:    f0dc7f9c6dd9 Merge git://git.kernel.org/pub/scm/linux/kern.. > git tree:       bpf-next > console output: https://syzkaller.appspot.com/x/log.txt?x=15ad7d10400000 > kernel config:  https://syzkaller.appspot.com/x/.config?x=fa9c20c48788d1c1 > dashboard link: https://syzkaller.appspot.com/bug?extid=457d3e2ffbcf31aee5c0 > compiler:       gcc (GCC) 8.0.1 20180413 (experimental) > syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1195225f800000 > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=171a7ce4400000 > > IMPORTANT: if you fix the bug, please add the following tag to the commit: > Reported-by: syzbot+457d3e2ffbcf31aee5c0@syzkaller.appspotmail.com > > ================================================================== > BUG: KASAN: use-after-free in dev_map_flush_old kernel/bpf/devmap.c:365 [inline] > BUG: KASAN: use-after-free in __dev_map_entry_free+0x2a8/0x300 kernel/bpf/devmap.c:379 > Read of size 8 at addr ffff8801b8da38c8 by task ksoftirqd/1/18 > > CPU: 1 PID: 18 Comm: ksoftirqd/1 Not tainted 4.17.0+ #39 > 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+0x1b9/0x294 lib/dump_stack.c:113 >  print_address_description+0x6c/0x20b mm/kasan/report.c:256 >  kasan_report_error mm/kasan/report.c:354 [inline] >  kasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412 >  __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433 >  dev_map_flush_old kernel/bpf/devmap.c:365 [inline] >  __dev_map_entry_free+0x2a8/0x300 kernel/bpf/devmap.c:379 >  __rcu_reclaim kernel/rcu/rcu.h:178 [inline] >  rcu_do_batch kernel/rcu/tree.c:2558 [inline] >  invoke_rcu_callbacks kernel/rcu/tree.c:2818 [inline] >  __rcu_process_callbacks kernel/rcu/tree.c:2785 [inline] >  rcu_process_callbacks+0xe9d/0x1760 kernel/rcu/tree.c:2802 >  __do_softirq+0x2e0/0xaf5 kernel/softirq.c:284 >  run_ksoftirqd+0x86/0x100 kernel/softirq.c:645 >  smpboot_thread_fn+0x417/0x870 kernel/smpboot.c:164 >  kthread+0x345/0x410 kernel/kthread.c:240 >  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412 > > Allocated by task 6675: >  save_stack+0x43/0xd0 mm/kasan/kasan.c:448 >  set_track mm/kasan/kasan.c:460 [inline] >  kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553 >  kmem_cache_alloc_trace+0x152/0x780 mm/slab.c:3620 >  kmalloc include/linux/slab.h:513 [inline] >  kzalloc include/linux/slab.h:706 [inline] >  dev_map_alloc+0x208/0x7f0 kernel/bpf/devmap.c:102 >  find_and_alloc_map kernel/bpf/syscall.c:129 [inline] >  map_create+0x393/0x1010 kernel/bpf/syscall.c:453 >  __do_sys_bpf kernel/bpf/syscall.c:2351 [inline] >  __se_sys_bpf kernel/bpf/syscall.c:2328 [inline] >  __x64_sys_bpf+0x303/0x510 kernel/bpf/syscall.c:2328 >  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:290 >  entry_SYSCALL_64_after_hwframe+0x49/0xbe > > Freed by task 26: >  save_stack+0x43/0xd0 mm/kasan/kasan.c:448 >  set_track mm/kasan/kasan.c:460 [inline] >  __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521 >  kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528 >  __cache_free mm/slab.c:3498 [inline] >  kfree+0xd9/0x260 mm/slab.c:3813 >  dev_map_free+0x4fa/0x670 kernel/bpf/devmap.c:191 >  bpf_map_free_deferred+0xba/0xf0 kernel/bpf/syscall.c:262 >  process_one_work+0xc64/0x1b70 kernel/workqueue.c:2153 >  worker_thread+0x181/0x13a0 kernel/workqueue.c:2296 >  kthread+0x345/0x410 kernel/kthread.c:240 >  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412 > > The buggy address belongs to the object at ffff8801b8da37c0 >  which belongs to the cache kmalloc-512 of size 512 > The buggy address is located 264 bytes inside of >  512-byte region [ffff8801b8da37c0, ffff8801b8da39c0) > The buggy address belongs to the page: > page:ffffea0006e368c0 count:1 mapcount:0 mapping:ffff8801da800940 index:0xffff8801b8da3540 > flags: 0x2fffc0000000100(slab) > raw: 02fffc0000000100 ffffea0007217b88 ffffea0006e30cc8 ffff8801da800940 > raw: ffff8801b8da3540 ffff8801b8da3040 0000000100000004 0000000000000000 > page dumped because: kasan: bad access detected > > Memory state around the buggy address: >  ffff8801b8da3780: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb >  ffff8801b8da3800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >> ffff8801b8da3880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >                                               ^ >  ffff8801b8da3900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >  ffff8801b8da3980: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc > ================================================================== > > > --- > This bug 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 bug report. See: > https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with syzbot. > syzbot can test patches for this bug, for details see: > https://goo.gl/tpsmEJ#testing-patches What about something like : diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c index 191b79948424f4b21b7aa120abc03801264bf0a6..1e525d70f83354e451b738ffb8e42d83b5fa932f 100644 --- a/kernel/bpf/devmap.c +++ b/kernel/bpf/devmap.c @@ -164,6 +164,9 @@ static void dev_map_free(struct bpf_map *map) bpf_clear_redirect_map(map); synchronize_rcu(); + /* Make sure prior __dev_map_entry_free() have completed. */ + rcu_barrier(); + /* To ensure all pending flush operations have completed wait for flush * bitmap to indicate all flush_needed bits to be zero on _all_ cpus. * Because the above synchronize_rcu() ensures the map is disconnected