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    Subject[PATCH 4.15 111/146] netfilter: x_tables: fix missing timer initialization in xt_LED
    Date
    4.15-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Paolo Abeni <pabeni@redhat.com>

    commit 10414014bc085aac9f787a5890b33b5605fbcfc4 upstream.

    syzbot reported that xt_LED may try to use the ledinternal->timer
    without previously initializing it:

    ------------[ cut here ]------------
    kernel BUG at kernel/time/timer.c:958!
    invalid opcode: 0000 [#1] SMP KASAN
    Dumping ftrace buffer:
    (ftrace buffer empty)
    Modules linked in:
    CPU: 1 PID: 1826 Comm: kworker/1:2 Not tainted 4.15.0+ #306
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
    Google 01/01/2011
    Workqueue: ipv6_addrconf addrconf_dad_work
    RIP: 0010:__mod_timer kernel/time/timer.c:958 [inline]
    RIP: 0010:mod_timer+0x7d6/0x13c0 kernel/time/timer.c:1102
    RSP: 0018:ffff8801d24fe9f8 EFLAGS: 00010293
    RAX: ffff8801d25246c0 RBX: ffff8801aec6cb50 RCX: ffffffff816052c6
    RDX: 0000000000000000 RSI: 00000000fffbd14b RDI: ffff8801aec6cb68
    RBP: ffff8801d24fec98 R08: 0000000000000000 R09: 1ffff1003a49fd6c
    R10: ffff8801d24feb28 R11: 0000000000000005 R12: dffffc0000000000
    R13: ffff8801d24fec70 R14: 00000000fffbd14b R15: ffff8801af608f90
    FS: 0000000000000000(0000) GS:ffff8801db500000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 00000000206d6fd0 CR3: 0000000006a22001 CR4: 00000000001606e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
    led_tg+0x1db/0x2e0 net/netfilter/xt_LED.c:75
    ip6t_do_table+0xc2a/0x1a30 net/ipv6/netfilter/ip6_tables.c:365
    ip6table_raw_hook+0x65/0x80 net/ipv6/netfilter/ip6table_raw.c:42
    nf_hook_entry_hookfn include/linux/netfilter.h:120 [inline]
    nf_hook_slow+0xba/0x1a0 net/netfilter/core.c:483
    nf_hook.constprop.27+0x3f6/0x830 include/linux/netfilter.h:243
    NF_HOOK include/linux/netfilter.h:286 [inline]
    ndisc_send_skb+0xa51/0x1370 net/ipv6/ndisc.c:491
    ndisc_send_ns+0x38a/0x870 net/ipv6/ndisc.c:633
    addrconf_dad_work+0xb9e/0x1320 net/ipv6/addrconf.c:4008
    process_one_work+0xbbf/0x1af0 kernel/workqueue.c:2113
    worker_thread+0x223/0x1990 kernel/workqueue.c:2247
    kthread+0x33c/0x400 kernel/kthread.c:238
    ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:429
    Code: 85 2a 0b 00 00 4d 8b 3c 24 4d 85 ff 75 9f 4c 8b bd 60 fd ff ff e8 bb
    57 10 00 65 ff 0d 94 9a a1 7e e9 d9 fc ff ff e8 aa 57 10 00 <0f> 0b e8 a3
    57 10 00 e9 14 fb ff ff e8 99 57 10 00 4c 89 bd 70
    RIP: __mod_timer kernel/time/timer.c:958 [inline] RSP: ffff8801d24fe9f8
    RIP: mod_timer+0x7d6/0x13c0 kernel/time/timer.c:1102 RSP: ffff8801d24fe9f8
    ---[ end trace f661ab06f5dd8b3d ]---

    The ledinternal struct can be shared between several different
    xt_LED targets, but the related timer is currently initialized only
    if the first target requires it. Fix it by unconditionally
    initializing the timer struct.

    v1 -> v2: call del_timer_sync() unconditionally, too.

    Fixes: 268cb38e1802 ("netfilter: x_tables: add LED trigger target")
    Reported-by: syzbot+10c98dc5725c6c8fc7fb@syzkaller.appspotmail.com
    Signed-off-by: Paolo Abeni <pabeni@redhat.com>
    Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    net/netfilter/xt_LED.c | 10 +++++-----
    1 file changed, 5 insertions(+), 5 deletions(-)

    --- a/net/netfilter/xt_LED.c
    +++ b/net/netfilter/xt_LED.c
    @@ -142,9 +142,10 @@ static int led_tg_check(const struct xt_
    goto exit_alloc;
    }

    - /* See if we need to set up a timer */
    - if (ledinfo->delay > 0)
    - timer_setup(&ledinternal->timer, led_timeout_callback, 0);
    + /* Since the letinternal timer can be shared between multiple targets,
    + * always set it up, even if the current target does not need it
    + */
    + timer_setup(&ledinternal->timer, led_timeout_callback, 0);

    list_add_tail(&ledinternal->list, &xt_led_triggers);

    @@ -181,8 +182,7 @@ static void led_tg_destroy(const struct

    list_del(&ledinternal->list);

    - if (ledinfo->delay > 0)
    - del_timer_sync(&ledinternal->timer);
    + del_timer_sync(&ledinternal->timer);

    led_trigger_unregister(&ledinternal->netfilter_led_trigger);


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