Re: KASAN: use-after-free Read in bpf_tcp_close

[Daniel Borkmann]

[ +John ]

On 05/26/2018 10:54 AM, syzbot wrote:
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:ÂÂÂ 3fb48d881dbe Merge branch 'bpf-fib-mtu-check'
> git tree:ÂÂÂÂÂÂ bpf-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=15fc1977800000
> kernel config:Â https://syzkaller.appspot.com/x/.config?x=b632d8e2c2ab2c1
> dashboard link: https://syzkaller.appspot.com/bug?extid=fce8f2462c403d02af98
> compiler:ÂÂÂÂÂÂ gcc (GCC) 8.0.1 20180413 (experimental)
> syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=1310c857800000
> C reproducer:ÂÂ https://syzkaller.appspot.com/x/repro.c?x=17de7177800000
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+fce8f2462c403d02af98@xxxxxxxxxxxxxxxxxxxxxxxxx

Should be fixed by: https://patchwork.ozlabs.org/patch/920695/

> ==================================================================
> BUG: KASAN: use-after-free in hlist_del_rcu include/linux/rculist.h:427 [inline]
> BUG: KASAN: use-after-free in bpf_tcp_close+0xd7f/0xf80 kernel/bpf/sockmap.c:271
> Read of size 8 at addr ffff8801c884cf90 by task syz-executor330/11778
> 
> CPU: 1 PID: 11778 Comm: syz-executor330 Not tainted 4.17.0-rc4+ #18
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
> Â__dump_stack lib/dump_stack.c:77 [inline]
> Âdump_stack+0x1b9/0x294 lib/dump_stack.c:113
> Âprint_address_description+0x6c/0x20b mm/kasan/report.c:256
> Âkasan_report_error mm/kasan/report.c:354 [inline]
> Âkasan_report.cold.7+0x242/0x2fe mm/kasan/report.c:412
> Â__asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:433
> Âhlist_del_rcu include/linux/rculist.h:427 [inline]
> Âbpf_tcp_close+0xd7f/0xf80 kernel/bpf/sockmap.c:271
> Âinet_release+0x104/0x1f0 net/ipv4/af_inet.c:427
> Âinet6_release+0x50/0x70 net/ipv6/af_inet6.c:459
> Âsock_release+0x96/0x1b0 net/socket.c:594
> Âsock_close+0x16/0x20 net/socket.c:1149
> Â__fput+0x34d/0x890 fs/file_table.c:209
> Â____fput+0x15/0x20 fs/file_table.c:243
> Âtask_work_run+0x1e4/0x290 kernel/task_work.c:113
> Âexit_task_work include/linux/task_work.h:22 [inline]
> Âdo_exit+0x1aee/0x2730 kernel/exit.c:865
> Âdo_group_exit+0x16f/0x430 kernel/exit.c:968
> Âget_signal+0x886/0x1960 kernel/signal.c:2469
> Âdo_signal+0x98/0x2040 arch/x86/kernel/signal.c:810
> Âexit_to_usermode_loop+0x28a/0x310 arch/x86/entry/common.c:162
> Âprepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
> Âsyscall_return_slowpath arch/x86/entry/common.c:265 [inline]
> Âdo_syscall_64+0x6ac/0x800 arch/x86/entry/common.c:290
> Âentry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x445ed9
> RSP: 002b:00007f0078c0adb8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
> RAX: fffffffffffffe00 RBX: 00000000006dbc24 RCX: 0000000000445ed9
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000006dbc24
> RBP: 00000000006dbc20 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
> R13: 00007ffcd147dbef R14: 00007f0078c0b9c0 R15: 0000000000000007
> 
> Allocated by task 11787:
> Âsave_stack+0x43/0xd0 mm/kasan/kasan.c:448
> Âset_track mm/kasan/kasan.c:460 [inline]
> Âkasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
> Â__do_kmalloc_node mm/slab.c:3682 [inline]
> Â__kmalloc_node+0x47/0x70 mm/slab.c:3689
> Âkmalloc_node include/linux/slab.h:554 [inline]
> Âalloc_sock_hash_elem kernel/bpf/sockmap.c:2114 [inline]
> Âsock_hash_ctx_update_elem.isra.23+0xa57/0x1560 kernel/bpf/sockmap.c:2245
> Âsock_hash_update_elem+0x14f/0x2d0 kernel/bpf/sockmap.c:2303
> Âmap_update_elem+0x5c4/0xc90 kernel/bpf/syscall.c:760
> Â__do_sys_bpf kernel/bpf/syscall.c:2134 [inline]
> Â__se_sys_bpf kernel/bpf/syscall.c:2105 [inline]
> Â__x64_sys_bpf+0x32a/0x4f0 kernel/bpf/syscall.c:2105
> Âdo_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
> Âentry_SYSCALL_64_after_hwframe+0x49/0xbe
> 
> Freed by task 8998:
> Âsave_stack+0x43/0xd0 mm/kasan/kasan.c:448
> Âset_track mm/kasan/kasan.c:460 [inline]
> Â__kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
> Âkasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
> Â__cache_free mm/slab.c:3498 [inline]
> Âkfree+0xd9/0x260 mm/slab.c:3813
> Âsock_hash_free+0x24e/0x6e0 kernel/bpf/sockmap.c:2093
> Âbpf_map_free_deferred+0xba/0xf0 kernel/bpf/syscall.c:259
> Âprocess_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
> Âworker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
> Âkthread+0x345/0x410 kernel/kthread.c:238
> Âret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
> 
> The buggy address belongs to the object at ffff8801c884cf80
> Âwhich belongs to the cache kmalloc-64 of size 64
> The buggy address is located 16 bytes inside of
> Â64-byte region [ffff8801c884cf80, ffff8801c884cfc0)
> The buggy address belongs to the page:
> page:ffffea0007221300 count:1 mapcount:0 mapping:ffff8801c884c000 index:0x0
> flags: 0x2fffc0000000100(slab)
> raw: 02fffc0000000100 ffff8801c884c000 0000000000000000 0000000100000020
> raw: ffffea00072e08e0 ffffea0006e99660 ffff8801da800340 0000000000000000
> page dumped because: kasan: bad access detected
> 
> Memory state around the buggy address:
> Âffff8801c884ce80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> Âffff8801c884cf00: 00 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc
>> ffff8801c884cf80: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc
> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ ^
> Âffff8801c884d000: fc fc fc fc fc fc fc fc fb fb fb fb fb fb fb fb
> Âffff8801c884d080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ==================================================================
> 
> 
> ---
> This bug is generated by a bot. It may contain errors.
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> 
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