Re: [syzbot] Re: [syzbot] [net?] WARNING: refcount bug in ethnl_phy_done

From: syzbot
Date: Fri Sep 13 2024 - 03:27:54 EST


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Subject: Re: [syzbot] [net?] WARNING: refcount bug in ethnl_phy_done
Author: lizhi.xu@xxxxxxxxxxxxx

Distinguish whether dev is initialized by phy start or phy doit

#syz test

diff --git a/net/ethtool/phy.c b/net/ethtool/phy.c
index 4ef7c6e32d10..fe11de6bddab 100644
--- a/net/ethtool/phy.c
+++ b/net/ethtool/phy.c
@@ -13,6 +13,7 @@
struct phy_req_info {
struct ethnl_req_info base;
struct phy_device_node *pdn;
+ u8 dev_start_doit;
};

#define PHY_REQINFO(__req_base) \
@@ -157,6 +158,9 @@ int ethnl_phy_doit(struct sk_buff *skb, struct genl_info *info)
if (ret < 0)
return ret;

+ if (req_info.base.dev)
+ req_info.dev_start_doit = 0;
+
rtnl_lock();

ret = ethnl_phy_parse_request(&req_info.base, tb, info->extack);
@@ -223,10 +227,14 @@ int ethnl_phy_start(struct netlink_callback *cb)
false);
ctx->ifindex = 0;
ctx->phy_index = 0;
+ ctx->phy_req_info->dev_start_doit = 0;

if (ret)
kfree(ctx->phy_req_info);

+ if (ctx->phy_req_info->base.dev)
+ ctx->phy_req_info->dev_start_doit = 1;
+
return ret;
}

@@ -234,7 +242,7 @@ int ethnl_phy_done(struct netlink_callback *cb)
{
struct ethnl_phy_dump_ctx *ctx = (void *)cb->ctx;

- if (ctx->phy_req_info->base.dev)
+ if (ctx->phy_req_info->base.dev && ctx->phy_req_info->dev_start_doit)
ethnl_parse_header_dev_put(&ctx->phy_req_info->base);

kfree(ctx->phy_req_info);