netdev - Re: [PATCHv3 net] bonding: fix missed rcu protection

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Message-ID: <20220519143142.ox36nj7uvq2sq3fr@skbuf>
Date:   Thu, 19 May 2022 14:31:43 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Hangbin Liu <liuhangbin@...il.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Jay Vosburgh <j.vosburgh@...il.com>,
        Veaceslav Falico <vfalico@...il.com>,
        Andy Gospodarek <andy@...yhouse.net>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        David Ahern <dsahern@...il.com>,
        Jonathan Toppins <jtoppins@...hat.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Paolo Abeni <pabeni@...hat.com>,
        "syzbot+92beb3d46aab498710fa@...kaller.appspotmail.com" 
        <syzbot+92beb3d46aab498710fa@...kaller.appspotmail.com>
Subject: Re: [PATCHv3 net] bonding: fix missed rcu protection

On Thu, May 19, 2022 at 10:01:48AM +0800, Hangbin Liu wrote:
> When removing the rcu_read_lock in bond_ethtool_get_ts_info() as
> discussed [1], I didn't notice it could be called via setsockopt,
> which doesn't hold rcu lock, as syzbot pointed:
> 
>   stack backtrace:
>   CPU: 0 PID: 3599 Comm: syz-executor317 Not tainted 5.18.0-rc5-syzkaller-01392-g01f4685797a5 #0
>   Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
>   Call Trace:
>    <TASK>
>    __dump_stack lib/dump_stack.c:88 [inline]
>    dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
>    bond_option_active_slave_get_rcu include/net/bonding.h:353 [inline]
>    bond_ethtool_get_ts_info+0x32c/0x3a0 drivers/net/bonding/bond_main.c:5595
>    __ethtool_get_ts_info+0x173/0x240 net/ethtool/common.c:554
>    ethtool_get_phc_vclocks+0x99/0x110 net/ethtool/common.c:568
>    sock_timestamping_bind_phc net/core/sock.c:869 [inline]
>    sock_set_timestamping+0x3a3/0x7e0 net/core/sock.c:916
>    sock_setsockopt+0x543/0x2ec0 net/core/sock.c:1221
>    __sys_setsockopt+0x55e/0x6a0 net/socket.c:2223
>    __do_sys_setsockopt net/socket.c:2238 [inline]
>    __se_sys_setsockopt net/socket.c:2235 [inline]
>    __x64_sys_setsockopt+0xba/0x150 net/socket.c:2235
>    do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>    do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>    entry_SYSCALL_64_after_hwframe+0x44/0xae
>   RIP: 0033:0x7f8902c8eb39
> 
> Fix it by adding rcu_read_lock and take a ref on the real_dev.
> Since dev_hold() and dev_put() can take NULL these days, we can
> skip checking if real_dev exist.
> 
> [1] https://lore.kernel.org/netdev/27565.1642742439@famine/
> 
> Reported-by: syzbot+92beb3d46aab498710fa@...kaller.appspotmail.com
> Fixes: aa6034678e87 ("bonding: use rcu_dereference_rtnl when get bonding active slave")
> Suggested-by: Vladimir Oltean <vladimir.oltean@....com>
> Suggested-by: Jakub Kicinski <kuba@...nel.org>
> Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> ---

Reviewed-by: Vladimir Oltean <vladimir.oltean@....com>