[PATCH net] flow_dissector: fix false-positive __read_overflow2_field() warning

[PATCH net] flow_dissector: fix false-positive __read_overflow2_field() warning

[Jakub Kicinski]

Bounds checking is unhappy that we try to copy both Ethernet
addresses but pass pointer to the first one. Luckily destination
address is the first field so pass the pointer to the entire header,
whatever.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
I feel like we talked about this one.
I wonder if my position now is consistent with what I said
in the past :)

 net/core/flow_dissector.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/core/flow_dissector.c b/net/core/flow_dissector.c
index 03b6e649c428..912bda212db2 100644
--- a/net/core/flow_dissector.c
+++ b/net/core/flow_dissector.c
@@ -1032,7 +1032,7 @@ bool __skb_flow_dissect(const struct net *net,
 		key_eth_addrs = skb_flow_dissector_target(flow_dissector,
 							  FLOW_DISSECTOR_KEY_ETH_ADDRS,
 							  target_container);
-		memcpy(key_eth_addrs, &eth->h_dest, sizeof(*key_eth_addrs));
+		memcpy(key_eth_addrs, eth, sizeof(*key_eth_addrs));
 	}
 
 proto_again:
-- 
2.34.1

Re: [PATCH net] flow_dissector: fix false-positive __read_overflow2_field() warning

[Kees Cook]

On Wed, Apr 06, 2022 at 02:15:21PM -0700, Jakub Kicinski wrote:
> Bounds checking is unhappy that we try to copy both Ethernet
> addresses but pass pointer to the first one. Luckily destination
> address is the first field so pass the pointer to the entire header,
> whatever.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Ah yes, thanks! I had prepared this patch last week, but failed to
actually send it. :|

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook

Re: [PATCH net] flow_dissector: fix false-positive __read_overflow2_field() warning

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <davem@davemloft.net>:

On Wed,  6 Apr 2022 14:15:21 -0700 you wrote:
> Bounds checking is unhappy that we try to copy both Ethernet
> addresses but pass pointer to the first one. Luckily destination
> address is the first field so pass the pointer to the entire header,
> whatever.
> 
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
> 
> [...]

Here is the summary with links:
  - [net] flow_dissector: fix false-positive __read_overflow2_field() warning
    https://git.kernel.org/netdev/net/c/1b808993e194

You are awesome, thank you!
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