[PATCH] netfilter: ipset: Replace strlcpy with strscpy

[PATCH] netfilter: ipset: Replace strlcpy with strscpy

[Azeem Shaikh]

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().

Direct replacement is safe here since return value from all
callers of STRLCPY macro were ignored.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
---
 net/netfilter/ipset/ip_set_hash_netiface.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/net/netfilter/ipset/ip_set_hash_netiface.c b/net/netfilter/ipset/ip_set_hash_netiface.c
index 031073286236..95aeb31c60e0 100644
--- a/net/netfilter/ipset/ip_set_hash_netiface.c
+++ b/net/netfilter/ipset/ip_set_hash_netiface.c
@@ -40,7 +40,7 @@ MODULE_ALIAS("ip_set_hash:net,iface");
 #define IP_SET_HASH_WITH_MULTI
 #define IP_SET_HASH_WITH_NET0
 
-#define STRLCPY(a, b)	strlcpy(a, b, IFNAMSIZ)
+#define STRSCPY(a, b)	strscpy(a, b, IFNAMSIZ)
 
 /* IPv4 variant */
 
@@ -182,11 +182,11 @@ hash_netiface4_kadt(struct ip_set *set, const struct sk_buff *skb,
 
 		if (!eiface)
 			return -EINVAL;
-		STRLCPY(e.iface, eiface);
+		STRSCPY(e.iface, eiface);
 		e.physdev = 1;
 #endif
 	} else {
-		STRLCPY(e.iface, SRCDIR ? IFACE(in) : IFACE(out));
+		STRSCPY(e.iface, SRCDIR ? IFACE(in) : IFACE(out));
 	}
 
 	if (strlen(e.iface) == 0)
@@ -400,11 +400,11 @@ hash_netiface6_kadt(struct ip_set *set, const struct sk_buff *skb,
 
 		if (!eiface)
 			return -EINVAL;
-		STRLCPY(e.iface, eiface);
+		STRSCPY(e.iface, eiface);
 		e.physdev = 1;
 #endif
 	} else {
-		STRLCPY(e.iface, SRCDIR ? IFACE(in) : IFACE(out));
+		STRSCPY(e.iface, SRCDIR ? IFACE(in) : IFACE(out));
 	}
 
 	if (strlen(e.iface) == 0)
-- 
2.41.0.162.gfafddb0af9-goog

Re: [PATCH] netfilter: ipset: Replace strlcpy with strscpy

[Kees Cook]

On Tue, Jun 13, 2023 at 12:34:37AM +0000, Azeem Shaikh wrote:
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> 
> Direct replacement is safe here since return value from all
> callers of STRLCPY macro were ignored.

Yeah, the macro name is probably not super helpful here. It seems like
it should have originally be named IFNAME_CPY or something.

> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
> 
> Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>

But, regardless:

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

-- 
Kees Cook

Re: [PATCH] netfilter: ipset: Replace strlcpy with strscpy

[Simon Horman]

On Tue, Jun 13, 2023 at 12:34:37AM +0000, Azeem Shaikh wrote:
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> 
> Direct replacement is safe here since return value from all
> callers of STRLCPY macro were ignored.
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
> 
> Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>

Reviewed-by: Simon Horman <simon.horman@corigine.com>

Re: [PATCH] netfilter: ipset: Replace strlcpy with strscpy

[Jozsef Kadlecsik]

On Tue, 13 Jun 2023, Azeem Shaikh wrote:

> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> 
> Direct replacement is safe here since return value from all
> callers of STRLCPY macro were ignored.
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
> 
> Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>

Acked-by: Jozsef Kadlecsik <kadlec@netfilter.org>

Best regards,
Jozsef

> ---
>  net/netfilter/ipset/ip_set_hash_netiface.c |   10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/net/netfilter/ipset/ip_set_hash_netiface.c b/net/netfilter/ipset/ip_set_hash_netiface.c
> index 031073286236..95aeb31c60e0 100644
> --- a/net/netfilter/ipset/ip_set_hash_netiface.c
> +++ b/net/netfilter/ipset/ip_set_hash_netiface.c
> @@ -40,7 +40,7 @@ MODULE_ALIAS("ip_set_hash:net,iface");
>  #define IP_SET_HASH_WITH_MULTI
>  #define IP_SET_HASH_WITH_NET0
>  
> -#define STRLCPY(a, b)	strlcpy(a, b, IFNAMSIZ)
> +#define STRSCPY(a, b)	strscpy(a, b, IFNAMSIZ)
>  
>  /* IPv4 variant */
>  
> @@ -182,11 +182,11 @@ hash_netiface4_kadt(struct ip_set *set, const struct sk_buff *skb,
>  
>  		if (!eiface)
>  			return -EINVAL;
> -		STRLCPY(e.iface, eiface);
> +		STRSCPY(e.iface, eiface);
>  		e.physdev = 1;
>  #endif
>  	} else {
> -		STRLCPY(e.iface, SRCDIR ? IFACE(in) : IFACE(out));
> +		STRSCPY(e.iface, SRCDIR ? IFACE(in) : IFACE(out));
>  	}
>  
>  	if (strlen(e.iface) == 0)
> @@ -400,11 +400,11 @@ hash_netiface6_kadt(struct ip_set *set, const struct sk_buff *skb,
>  
>  		if (!eiface)
>  			return -EINVAL;
> -		STRLCPY(e.iface, eiface);
> +		STRSCPY(e.iface, eiface);
>  		e.physdev = 1;
>  #endif
>  	} else {
> -		STRLCPY(e.iface, SRCDIR ? IFACE(in) : IFACE(out));
> +		STRSCPY(e.iface, SRCDIR ? IFACE(in) : IFACE(out));
>  	}
>  
>  	if (strlen(e.iface) == 0)
> -- 
> 2.41.0.162.gfafddb0af9-goog
> 
> 
> 

-
E-mail  : kadlec@blackhole.kfki.hu, kadlecsik.jozsef@wigner.hu
PGP key : https://wigner.hu/~kadlec/pgp_public_key.txt
Address : Wigner Research Centre for Physics
          H-1525 Budapest 114, POB. 49, Hungary

Re: [PATCH] netfilter: ipset: Replace strlcpy with strscpy

[Kees Cook]

On Tue, 13 Jun 2023 00:34:37 +0000, Azeem Shaikh wrote:
> strlcpy() reads the entire source buffer first.
> This read may exceed the destination size limit.
> This is both inefficient and can lead to linear read
> overflows if a source string is not NUL-terminated [1].
> In an effort to remove strlcpy() completely [2], replace
> strlcpy() here with strscpy().
> 
> [...]

Since this got Acked and it's a trivial change, I'll take this via the
hardening tree. Thanks!

Applied to for-next/hardening, thanks!

[1/1] netfilter: ipset: Replace strlcpy with strscpy
      https://git.kernel.org/kees/c/0b2fa86361f4

-- 
Kees Cook