diff mbox series

hamradio: baycom_epp: Fix return type of baycom_send_packet()

Message ID 20221102160610.1186145-1-nathan@kernel.org
State New
Headers
Series hamradio: baycom_epp: Fix return type of baycom_send_packet() |

Commit Message

Nathan Chancellor Nov. 2, 2022, 4:06 p.m. UTC 
  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/hamradio/baycom_epp.c:1119:25: 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      = baycom_send_packet,
                                ^~~~~~~~~~~~~~~~~~
  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 baycom_send_packet()
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>
---
 drivers/net/hamradio/baycom_epp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)


base-commit: 9abf2313adc1ca1b6180c508c25f22f9395cc780

Comments

Kees Cook Nov. 2, 2022, 7:08 p.m. UTC | #1 
On Wed, Nov 02, 2022 at 09:06:10AM -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/hamradio/baycom_epp.c:1119:25: 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      = baycom_send_packet,
>                                 ^~~~~~~~~~~~~~~~~~
>   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 baycom_send_packet()
> 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>

Heh, this one was already using the enum for the argument to "return",
too. :)

Reviewed-by: Kees Cook <keescook@chromium.org>
patchwork-bot+netdevbpf@kernel.org Nov. 4, 2022, 5 a.m. UTC | #2 
Hello:

This patch was applied to netdev/net-next.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Wed,  2 Nov 2022 09:06:10 -0700 you 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:
> 
> [...]

Here is the summary with links:
  - hamradio: baycom_epp: Fix return type of baycom_send_packet()
    https://git.kernel.org/netdev/net-next/c/c5733e5b15d9

You are awesome, thank you!
diff mbox series

Patch

diff --git a/drivers/net/hamradio/baycom_epp.c b/drivers/net/hamradio/baycom_epp.c
index 791b4a53d69f..bd3b0c2655a2 100644
--- a/drivers/net/hamradio/baycom_epp.c
+++ b/drivers/net/hamradio/baycom_epp.c
@@ -758,7 +758,7 @@  static void epp_bh(struct work_struct *work)
  * ===================== network driver interface =========================
  */
 
-static int baycom_send_packet(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t baycom_send_packet(struct sk_buff *skb, struct net_device *dev)
 {
 	struct baycom_state *bc = netdev_priv(dev);