[PATCH][net-next] netfilter: ebtables: use array_size() helper in copy_{from,to}_user()

[PATCH][net-next] netfilter: ebtables: use array_size() helper in copy_{from,to}_user()

[Gustavo A. R. Silva]

Use array_size() helper instead of the open-coded version in
copy_{from,to}_user().  These sorts of multiplication factors
need to be wrapped in array_size().

Link: https://github.com/KSPP/linux/issues/160
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
---
 net/bridge/netfilter/ebtables.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/bridge/netfilter/ebtables.c b/net/bridge/netfilter/ebtables.c
index 83d1798dfbb4..32fa05ec4a6d 100644
--- a/net/bridge/netfilter/ebtables.c
+++ b/net/bridge/netfilter/ebtables.c
@@ -1071,7 +1071,7 @@ static int do_replace_finish(struct net *net, struct ebt_replace *repl,
 	 */
 	if (repl->num_counters &&
 	   copy_to_user(repl->counters, counterstmp,
-	   repl->num_counters * sizeof(struct ebt_counter))) {
+	   array_size(repl->num_counters, sizeof(struct ebt_counter)))) {
 		/* Silent error, can't fail, new table is already in place */
 		net_warn_ratelimited("ebtables: counters copy to user failed while replacing table\n");
 	}
@@ -1399,7 +1399,8 @@ static int do_update_counters(struct net *net, const char *name,
 		goto unlock_mutex;
 	}
 
-	if (copy_from_user(tmp, counters, num_counters * sizeof(*counters))) {
+	if (copy_from_user(tmp, counters,
+			   array_size(num_counters, sizeof(*counters)))) {
 		ret = -EFAULT;
 		goto unlock_mutex;
 	}
@@ -1532,7 +1533,7 @@ static int copy_counters_to_user(struct ebt_table *t,
 	write_unlock_bh(&t->lock);
 
 	if (copy_to_user(user, counterstmp,
-	   nentries * sizeof(struct ebt_counter)))
+	    array_size(nentries, sizeof(struct ebt_counter))))
 		ret = -EFAULT;
 	vfree(counterstmp);
 	return ret;
-- 
2.27.0

Re: [PATCH][net-next] netfilter: ebtables: use array_size() helper in copy_{from,to}_user()

[Kees Cook]

On Tue, Sep 28, 2021 at 03:06:47PM -0500, Gustavo A. R. Silva wrote:
> Use array_size() helper instead of the open-coded version in
> copy_{from,to}_user().  These sorts of multiplication factors
> need to be wrapped in array_size().
> 
> Link: https://github.com/KSPP/linux/issues/160
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Thanks!

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

I see that this is marked "Awaiting Upstream" (for an ebtables
maintainer ack?)
https://patchwork.kernel.org/project/netdevbpf/patch/20210928200647.GA266402@embeddedor/

-- 
Kees Cook

Re: [PATCH][net-next] netfilter: ebtables: use array_size() helper in copy_{from,to}_user()

[Pablo Neira Ayuso]

On Thu, Oct 21, 2021 at 10:00:34AM -0700, Kees Cook wrote:
> On Tue, Sep 28, 2021 at 03:06:47PM -0500, Gustavo A. R. Silva wrote:
> > Use array_size() helper instead of the open-coded version in
> > copy_{from,to}_user().  These sorts of multiplication factors
> > need to be wrapped in array_size().
> > 
> > Link: https://github.com/KSPP/linux/issues/160
> > Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
> 
> Thanks!
> 
> Reviewed-by: Kees Cook <keescook@chromium.org>
> 
> I see that this is marked "Awaiting Upstream" (for an ebtables
> maintainer ack?)
> https://patchwork.kernel.org/project/netdevbpf/patch/20210928200647.GA266402@embeddedor/

I'll route this through the netfilter tree, thanks.