• Taehee Yoo's avatar
    net: bpfilter: disallow to remove bpfilter module while being used · 71a85084
    Taehee Yoo authored
    The bpfilter.ko module can be removed while functions of the bpfilter.ko
    are executing. so panic can occurred. in order to protect that, locks can
    be used. a bpfilter_lock protects routines in the
    __bpfilter_process_sockopt() but it's not enough because __exit routine
    can be executed concurrently.
    
    Now, the bpfilter_umh can not run in parallel.
    So, the module do not removed while it's being used and it do not
    double-create UMH process.
    The members of the umh_info and the bpfilter_umh_ops are protected by
    the bpfilter_umh_ops.lock.
    
    test commands:
       while :
       do
    	iptables -I FORWARD -m string --string ap --algo kmp &
    	modprobe -rv bpfilter &
       done
    
    splat looks like:
    [  298.623435] BUG: unable to handle kernel paging request at fffffbfff807440b
    [  298.628512] #PF error: [normal kernel read fault]
    [  298.633018] PGD 124327067 P4D 124327067 PUD 11c1a3067 PMD 119eb2067 PTE 0
    [  298.638859] Oops: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
    [  298.638859] CPU: 0 PID: 2997 Comm: iptables Not tainted 4.20.0+ #154
    [  298.638859] RIP: 0010:__mutex_lock+0x6b9/0x16a0
    [  298.638859] Code: c0 00 00 e8 89 82 ff ff 80 bd 8f fc ff ff 00 0f 85 d9 05 00 00 48 8b 85 80 fc ff ff 48 bf 00 00 00 00 00 fc ff df 48 c1 e8 03 <80> 3c 38 00 0f 85 1d 0e 00 00 48 8b 85 c8 fc ff ff 49 39 47 58 c6
    [  298.638859] RSP: 0018:ffff88810e7777a0 EFLAGS: 00010202
    [  298.638859] RAX: 1ffffffff807440b RBX: ffff888111bd4d80 RCX: 0000000000000000
    [  298.638859] RDX: 1ffff110235ff806 RSI: ffff888111bd5538 RDI: dffffc0000000000
    [  298.638859] RBP: ffff88810e777b30 R08: 0000000080000002 R09: 0000000000000000
    [  298.638859] R10: 0000000000000000 R11: 0000000000000000 R12: fffffbfff168a42c
    [  298.638859] R13: ffff888111bd4d80 R14: ffff8881040e9a05 R15: ffffffffc03a2000
    [  298.638859] FS:  00007f39e3758700(0000) GS:ffff88811ae00000(0000) knlGS:0000000000000000
    [  298.638859] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    [  298.638859] CR2: fffffbfff807440b CR3: 000000011243e000 CR4: 00000000001006f0
    [  298.638859] Call Trace:
    [  298.638859]  ? mutex_lock_io_nested+0x1560/0x1560
    [  298.638859]  ? kasan_kmalloc+0xa0/0xd0
    [  298.638859]  ? kmem_cache_alloc+0x1c2/0x260
    [  298.638859]  ? __alloc_file+0x92/0x3c0
    [  298.638859]  ? alloc_empty_file+0x43/0x120
    [  298.638859]  ? alloc_file_pseudo+0x220/0x330
    [  298.638859]  ? sock_alloc_file+0x39/0x160
    [  298.638859]  ? __sys_socket+0x113/0x1d0
    [  298.638859]  ? __x64_sys_socket+0x6f/0xb0
    [  298.638859]  ? do_syscall_64+0x138/0x560
    [  298.638859]  ? entry_SYSCALL_64_after_hwframe+0x49/0xbe
    [  298.638859]  ? __alloc_file+0x92/0x3c0
    [  298.638859]  ? init_object+0x6b/0x80
    [  298.638859]  ? cyc2ns_read_end+0x10/0x10
    [  298.638859]  ? cyc2ns_read_end+0x10/0x10
    [  298.638859]  ? hlock_class+0x140/0x140
    [  298.638859]  ? sched_clock_local+0xd4/0x140
    [  298.638859]  ? sched_clock_local+0xd4/0x140
    [  298.638859]  ? check_flags.part.37+0x440/0x440
    [  298.638859]  ? __lock_acquire+0x4f90/0x4f90
    [  298.638859]  ? set_rq_offline.part.89+0x140/0x140
    [ ... ]
    
    Fixes: d2ba09c1 ("net: add skeleton of bpfilter kernel module")
    Signed-off-by: default avatarTaehee Yoo <ap420073@gmail.com>
    Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
    71a85084
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