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    Subject[PATCH 5.4 43/71] sit: do not call ipip6_dev_free() from sit_init_net()
    Date
    From: Eric Dumazet <edumazet@google.com>

    [ Upstream commit e28587cc491ef0f3c51258fdc87fbc386b1d4c59 ]

    ipip6_dev_free is sit dev->priv_destructor, already called
    by register_netdevice() if something goes wrong.

    Alternative would be to make ipip6_dev_free() robust against
    multiple invocations, but other drivers do not implement this
    strategy.

    syzbot reported:

    dst_release underflow
    WARNING: CPU: 0 PID: 5059 at net/core/dst.c:173 dst_release+0xd8/0xe0 net/core/dst.c:173
    Modules linked in:
    CPU: 1 PID: 5059 Comm: syz-executor.4 Not tainted 5.16.0-rc5-syzkaller #0
    Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
    RIP: 0010:dst_release+0xd8/0xe0 net/core/dst.c:173
    Code: 4c 89 f2 89 d9 31 c0 5b 41 5e 5d e9 da d5 44 f9 e8 1d 90 5f f9 c6 05 87 48 c6 05 01 48 c7 c7 80 44 99 8b 31 c0 e8 e8 67 29 f9 <0f> 0b eb 85 0f 1f 40 00 53 48 89 fb e8 f7 8f 5f f9 48 83 c3 a8 48
    RSP: 0018:ffffc9000aa5faa0 EFLAGS: 00010246
    RAX: d6894a925dd15a00 RBX: 00000000ffffffff RCX: 0000000000040000
    RDX: ffffc90005e19000 RSI: 000000000003ffff RDI: 0000000000040000
    RBP: 0000000000000000 R08: ffffffff816a1f42 R09: ffffed1017344f2c
    R10: ffffed1017344f2c R11: 0000000000000000 R12: 0000607f462b1358
    R13: 1ffffffff1bfd305 R14: ffffe8ffffcb1358 R15: dffffc0000000000
    FS: 00007f66c71a2700(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
    CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 00007f88aaed5058 CR3: 0000000023e0f000 CR4: 00000000003506f0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
    <TASK>
    dst_cache_destroy+0x107/0x1e0 net/core/dst_cache.c:160
    ipip6_dev_free net/ipv6/sit.c:1414 [inline]
    sit_init_net+0x229/0x550 net/ipv6/sit.c:1936
    ops_init+0x313/0x430 net/core/net_namespace.c:140
    setup_net+0x35b/0x9d0 net/core/net_namespace.c:326
    copy_net_ns+0x359/0x5c0 net/core/net_namespace.c:470
    create_new_namespaces+0x4ce/0xa00 kernel/nsproxy.c:110
    unshare_nsproxy_namespaces+0x11e/0x180 kernel/nsproxy.c:226
    ksys_unshare+0x57d/0xb50 kernel/fork.c:3075
    __do_sys_unshare kernel/fork.c:3146 [inline]
    __se_sys_unshare kernel/fork.c:3144 [inline]
    __x64_sys_unshare+0x34/0x40 kernel/fork.c:3144
    do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
    entry_SYSCALL_64_after_hwframe+0x44/0xae
    RIP: 0033:0x7f66c882ce99
    Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 bc ff ff ff f7 d8 64 89 01 48
    RSP: 002b:00007f66c71a2168 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
    RAX: ffffffffffffffda RBX: 00007f66c893ff60 RCX: 00007f66c882ce99
    RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000048040200
    RBP: 00007f66c8886ff1 R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
    R13: 00007fff6634832f R14: 00007f66c71a2300 R15: 0000000000022000
    </TASK>

    Fixes: cf124db566e6 ("net: Fix inconsistent teardown and release of private netdev state.")
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Reported-by: syzbot <syzkaller@googlegroups.com>
    Link: https://lore.kernel.org/r/20211216111741.1387540-1-eric.dumazet@gmail.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    net/ipv6/sit.c | 1 -
    1 file changed, 1 deletion(-)

    diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
    index 7f9cae4c49e7e..16e75a996b749 100644
    --- a/net/ipv6/sit.c
    +++ b/net/ipv6/sit.c
    @@ -1876,7 +1876,6 @@ static int __net_init sit_init_net(struct net *net)
    return 0;

    err_reg_dev:
    - ipip6_dev_free(sitn->fb_tunnel_dev);
    free_netdev(sitn->fb_tunnel_dev);
    err_alloc_dev:
    return err;
    --
    2.33.0


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