[PATCH net-next] ethtool: always write dev in ethnl_parse_header_dev_get

Commit 0976b888a150 ("ethtool: fix null-ptr-deref on ref tracker")
made the write to req_info.dev conditional, but as Eric points out
in a different follow up the structure is often allocated on the
stack and not kzalloc()'d so seems safer to always write the dev,
in case it's garbage on input.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/ethtool/netlink.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index 767fb3f17267..f09c62302a9a 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c

@@ -141,10 +141,9 @@ int ethnl_parse_header_dev_get(struct ethnl_req_info *req_info,
 		return -EINVAL;
 	}
 
-	if (dev) {
-		req_info->dev = dev;
+	req_info->dev = dev;
+	if (dev)
 		netdev_tracker_alloc(dev, &req_info->dev_tracker, GFP_KERNEL);
-	}
 	req_info->flags = flags;
 	return 0;
 }

-- 
2.31.1

On 12/14/21 7:47 AM, Jakub Kicinski wrote:

Commit 0976b888a150 ("ethtool: fix null-ptr-deref on ref tracker")
made the write to req_info.dev conditional, but as Eric points out
in a different follow up the structure is often allocated on the
stack and not kzalloc()'d so seems safer to always write the dev,
in case it's garbage on input.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Yep, this was basically how I wanted to fix this.


Reviewed-by: Eric Dumazet <redacted>

Hello:

This patch was applied to netdev/net-next.git (master)
by David S. Miller [off-list ref]:

On Tue, 14 Dec 2021 07:47:25 -0800 you wrote:

Commit 0976b888a150 ("ethtool: fix null-ptr-deref on ref tracker")
made the write to req_info.dev conditional, but as Eric points out
in a different follow up the structure is often allocated on the
stack and not kzalloc()'d so seems safer to always write the dev,
in case it's garbage on input.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>

[...]

Here is the summary with links:
  - [net-next] ethtool: always write dev in ethnl_parse_header_dev_get
    https://git.kernel.org/netdev/net-next/c/3bc14ea0d12a

You are awesome, thank you!
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