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From: Kees Cook <keescook@chromium.org>
To: Nathan Chancellor <nathan@kernel.org>
Cc: "David S. Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	netdev@vger.kernel.org,
	Nick Desaulniers <ndesaulniers@google.com>,
	Tom Rix <trix@redhat.com>,
	Sami Tolvanen <samitolvanen@google.com>,
	llvm@lists.linux.dev, linux-kernel@vger.kernel.org,
	patches@lists.linux.dev
Subject: Re: [PATCH] net: ethernet: ti: Fix return type of netcp_ndo_start_xmit()
Date: Wed, 2 Nov 2022 12:08:12 -0700	[thread overview]
Message-ID: <202211021208.F66688DFF1@keescook> (raw)
In-Reply-To: <20221102160933.1601260-1-nathan@kernel.org>

On Wed, Nov 02, 2022 at 09:09:33AM -0700, Nathan Chancellor wrote:
> With clang's kernel control flow integrity (kCFI, CONFIG_CFI_CLANG),
> indirect call targets are validated against the expected function
> pointer prototype to make sure the call target is valid to help mitigate
> ROP attacks. If they are not identical, there is a failure at run time,
> which manifests as either a kernel panic or thread getting killed. A
> proposed warning in clang aims to catch these at compile time, which
> reveals:
> 
>   drivers/net/ethernet/ti/netcp_core.c:1944:21: error: incompatible function pointer types initializing 'netdev_tx_t (*)(struct sk_buff *, struct net_device *)' (aka 'enum netdev_tx (*)(struct sk_buff *, struct net_device *)') with an expression of type 'int (struct sk_buff *, struct net_device *)' [-Werror,-Wincompatible-function-pointer-types-strict]
>           .ndo_start_xmit         = netcp_ndo_start_xmit,
>                                     ^~~~~~~~~~~~~~~~~~~~
>   1 error generated.
> 
> ->ndo_start_xmit() in 'struct net_device_ops' expects a return type of
> 'netdev_tx_t', not 'int'. Adjust the return type of
> netcp_ndo_start_xmit() to match the prototype's to resolve the warning
> and CFI failure.
> 
> Link: https://github.com/ClangBuiltLinux/linux/issues/1750
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

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

-- 
Kees Cook

  reply	other threads:[~2022-11-02 19:08 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-02 16:09 [PATCH] net: ethernet: ti: Fix return type of netcp_ndo_start_xmit() Nathan Chancellor
2022-11-02 19:08 ` Kees Cook [this message]
2022-11-04  5:00 ` patchwork-bot+netdevbpf

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