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Message-ID: Subject: Re: KASAN: use-after-free Read in __dev_map_entry_free To: Eric Dumazet , Jesper Dangaard Brouer Cc: syzbot , Alexei Starovoitov , Daniel Borkmann , LKML , Network Development , syzkaller-bugs Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 2, 2019 at 1:03 PM Eric Dumazet wrote: > > > > 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(); > + Eric, Thank you for looking at it. The fix makes sense to me. Jesper, thoughts?