Patch "netfilter: nf_tables: nft_obj_filter fits into cb->ctx" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    netfilter: nf_tables: nft_obj_filter fits into cb->ctx

to the 6.1-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:
     netfilter-nf_tables-nft_obj_filter-fits-into-cb-ctx.patch
and it can be found in the queue-6.1 subdirectory.

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



commit 883be28063c1849b7ad0d0bdea6570577292279f
Author: Phil Sutter <phil@xxxxxx>
Date:   Fri Oct 20 19:34:32 2023 +0200

    netfilter: nf_tables: nft_obj_filter fits into cb->ctx
    
    [ Upstream commit 5a893b9cdf6fa5758f43d323a1d7fa6d1bf489ff ]
    
    No need to allocate it if one may just use struct netlink_callback's
    scratch area for it.
    
    Signed-off-by: Phil Sutter <phil@xxxxxx>
    Signed-off-by: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
    Stable-dep-of: bd662c4218f9 ("netfilter: nf_tables: Add locking for NFT_MSG_GETOBJ_RESET requests")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 48cd3e2dde69c..05c93af417120 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -7425,7 +7425,7 @@ struct nft_obj_dump_ctx {
 static int nf_tables_dump_obj(struct sk_buff *skb, struct netlink_callback *cb)
 {
 	const struct nfgenmsg *nfmsg = nlmsg_data(cb->nlh);
-	struct nft_obj_dump_ctx *ctx = cb->data;
+	struct nft_obj_dump_ctx *ctx = (void *)cb->ctx;
 	struct net *net = sock_net(skb->sk);
 	int family = nfmsg->nfgen_family;
 	struct nftables_pernet *nft_net;
@@ -7487,34 +7487,28 @@ static int nf_tables_dump_obj(struct sk_buff *skb, struct netlink_callback *cb)
 
 static int nf_tables_dump_obj_start(struct netlink_callback *cb)
 {
+	struct nft_obj_dump_ctx *ctx = (void *)cb->ctx;
 	const struct nlattr * const *nla = cb->data;
-	struct nft_obj_dump_ctx *ctx = NULL;
 
-	ctx = kzalloc(sizeof(*ctx), GFP_ATOMIC);
-	if (!ctx)
-		return -ENOMEM;
+	BUILD_BUG_ON(sizeof(*ctx) > sizeof(cb->ctx));
 
 	if (nla[NFTA_OBJ_TABLE]) {
 		ctx->table = nla_strdup(nla[NFTA_OBJ_TABLE], GFP_ATOMIC);
-		if (!ctx->table) {
-			kfree(ctx);
+		if (!ctx->table)
 			return -ENOMEM;
-		}
 	}
 
 	if (nla[NFTA_OBJ_TYPE])
 		ctx->type = ntohl(nla_get_be32(nla[NFTA_OBJ_TYPE]));
 
-	cb->data = ctx;
 	return 0;
 }
 
 static int nf_tables_dump_obj_done(struct netlink_callback *cb)
 {
-	struct nft_obj_dump_ctx *ctx = cb->data;
+	struct nft_obj_dump_ctx *ctx = (void *)cb->ctx;
 
 	kfree(ctx->table);
-	kfree(ctx);
 
 	return 0;
 }