Patch "s390/lcs: Fix return type of lcs_start_xmit()" has been added to the 6.0-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    s390/lcs: Fix return type of lcs_start_xmit()

to the 6.0-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     s390-lcs-fix-return-type-of-lcs_start_xmit.patch
and it can be found in the queue-6.0 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit d872c40b1c8995dbb6f617be00e36c82be97c33d
Author: Nathan Chancellor <nathan@xxxxxxxxxx>
Date:   Thu Nov 3 10:01:30 2022 -0700

    s390/lcs: Fix return type of lcs_start_xmit()
    
    [ Upstream commit bb16db8393658e0978c3f0d30ae069e878264fa3 ]
    
    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/s390/net/lcs.c:2090:21: 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         = lcs_start_xmit,
                                        ^~~~~~~~~~~~~~
      drivers/s390/net/lcs.c:2097:21: 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         = lcs_start_xmit,
                                        ^~~~~~~~~~~~~~
    
    ->ndo_start_xmit() in 'struct net_device_ops' expects a return type of
    'netdev_tx_t', not 'int'. Adjust the return type of lcs_start_xmit() to
    match the prototype's to resolve the warning and potential CFI failure,
    should s390 select ARCH_SUPPORTS_CFI_CLANG in the future.
    
    Link: https://github.com/ClangBuiltLinux/linux/issues/1750
    Reviewed-by: Alexandra Winter <wintera@xxxxxxxxxxxxx>
    Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx>
    Signed-off-by: Nathan Chancellor <nathan@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/s390/net/lcs.c b/drivers/s390/net/lcs.c
index 84c8981317b4..38f312664ce7 100644
--- a/drivers/s390/net/lcs.c
+++ b/drivers/s390/net/lcs.c
@@ -1519,9 +1519,8 @@ lcs_txbuffer_cb(struct lcs_channel *channel, struct lcs_buffer *buffer)
 /*
  * Packet transmit function called by network stack
  */
-static int
-__lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb,
-		 struct net_device *dev)
+static netdev_tx_t __lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb,
+				    struct net_device *dev)
 {
 	struct lcs_header *header;
 	int rc = NETDEV_TX_OK;
@@ -1582,8 +1581,7 @@ __lcs_start_xmit(struct lcs_card *card, struct sk_buff *skb,
 	return rc;
 }
 
-static int
-lcs_start_xmit(struct sk_buff *skb, struct net_device *dev)
+static netdev_tx_t lcs_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct lcs_card *card;
 	int rc;