[PATCH] net: 802: Use memset_startat() to clear struct fields

[PATCH] net: 802: Use memset_startat() to clear struct fields

[Kees Cook]

In preparation for FORTIFY_SOURCE performing compile-time and run-time
field bounds checking for memset(), avoid intentionally writing across
neighboring fields.

Use memset_startat() so memset() doesn't get confused about writing
beyond the destination member that is intended to be the starting point
of zeroing through the end of the struct.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
 net/802/hippi.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/802/hippi.c b/net/802/hippi.c
index 887e73d520e4..1997b7dd265e 100644
--- a/net/802/hippi.c
+++ b/net/802/hippi.c
@@ -65,7 +65,7 @@ static int hippi_header(struct sk_buff *skb, struct net_device *dev,
 	hip->le.src_addr_type	= 2;	/* 12 bit SC address */
 
 	memcpy(hip->le.src_switch_addr, dev->dev_addr + 3, 3);
-	memset(&hip->le.reserved, 0, 16);
+	memset_startat(&hip->le, 0, reserved);
 
 	hip->snap.dsap		= HIPPI_EXTENDED_SAP;
 	hip->snap.ssap		= HIPPI_EXTENDED_SAP;
-- 
2.30.2

Re: [PATCH] net: 802: Use memset_startat() to clear struct fields

[patchwork-bot+netdevbpf]

Hello:

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

On Thu, 18 Nov 2021 12:30:45 -0800 you wrote:
> In preparation for FORTIFY_SOURCE performing compile-time and run-time
> field bounds checking for memset(), avoid intentionally writing across
> neighboring fields.
> 
> Use memset_startat() so memset() doesn't get confused about writing
> beyond the destination member that is intended to be the starting point
> of zeroing through the end of the struct.
> 
> [...]

Here is the summary with links:
  - net: 802: Use memset_startat() to clear struct fields
    https://git.kernel.org/netdev/net-next/c/e3617433c3da

You are awesome, thank you!
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