net: ethtool: Fix the panic caused by dev being null when dumping coalesce

syzbot reported a general protection fault caused by a null pointer
dereference in coalesce_fill_reply(). The issue occurs when req_base->dev
is null, leading to an invalid memory access.

This panic occurs if dumping coalesce when no device name is specified.

Fixes: f750dfe825b9 ("ethtool: provide customized dim profile management")
Reported-by: syzbot+e77327e34cdc8c36b7d3@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=e77327e34cdc8c36b7d3
Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ethtool/coalesce.c b/net/ethtool/coalesce.c
index 759b16e3d13428a3bbe466ee1d156c1a18f6e156..3e18ca1ccc5ef663473afe79b4c135d8fb30ee5a 100644 (file)
--- a/net/ethtool/coalesce.c
+++ b/net/ethtool/coalesce.c
@@ -211,9 +211,9 @@ static int coalesce_fill_reply(struct sk_buff *skb,
 {
        const struct coalesce_reply_data *data = COALESCE_REPDATA(reply_base);
        const struct kernel_ethtool_coalesce *kcoal = &data->kernel_coalesce;
-       struct dim_irq_moder *moder = req_base->dev->irq_moder;
        const struct ethtool_coalesce *coal = &data->coalesce;
        u32 supported = data->supported_params;
+       struct dim_irq_moder *moder;
        int ret = 0;
 
        if (coalesce_put_u32(skb, ETHTOOL_A_COALESCE_RX_USECS,
@@ -272,9 +272,10 @@ static int coalesce_fill_reply(struct sk_buff *skb,
                             kcoal->tx_aggr_time_usecs, supported))
                return -EMSGSIZE;
 
-       if (!moder)
+       if (!req_base->dev || !req_base->dev->irq_moder)
                return 0;
 
+       moder = req_base->dev->irq_moder;
        rcu_read_lock();
        if (moder->profile_flags & DIM_PROFILE_RX) {
                ret = coalesce_put_profile(skb, ETHTOOL_A_COALESCE_RX_PROFILE,