Patch "bpf: Handle BPF_EXIST and BPF_NOEXIST for LPM trie" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

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

    bpf: Handle BPF_EXIST and BPF_NOEXIST for LPM trie

to the 5.10-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:
     bpf-handle-bpf_exist-and-bpf_noexist-for-lpm-trie.patch
and it can be found in the queue-5.10 subdirectory.

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



commit 76e6c8742f579214cf5d288a44f6bd092f761e63
Author: Hou Tao <houtao1@xxxxxxxxxx>
Date:   Fri Dec 6 19:06:16 2024 +0800

    bpf: Handle BPF_EXIST and BPF_NOEXIST for LPM trie
    
    [ Upstream commit eae6a075e9537dd69891cf77ca5a88fa8a28b4a1 ]
    
    Add the currently missing handling for the BPF_EXIST and BPF_NOEXIST
    flags. These flags can be specified by users and are relevant since LPM
    trie supports exact matches during update.
    
    Fixes: b95a5c4db09b ("bpf: add a longest prefix match trie map implementation")
    Reviewed-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
    Acked-by: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
    Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
    Link: https://lore.kernel.org/r/20241206110622.1161752-4-houtao@xxxxxxxxxxxxxxx
    Signed-off-by: Alexei Starovoitov <ast@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index 8370b391f1d6c..07f11f108f6ab 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -364,6 +364,10 @@ static int trie_update_elem(struct bpf_map *map,
 	 * simply assign the @new_node to that slot and be done.
 	 */
 	if (!node) {
+		if (flags == BPF_EXIST) {
+			ret = -ENOENT;
+			goto out;
+		}
 		rcu_assign_pointer(*slot, new_node);
 		goto out;
 	}
@@ -372,18 +376,31 @@ static int trie_update_elem(struct bpf_map *map,
 	 * which already has the correct data array set.
 	 */
 	if (node->prefixlen == matchlen) {
+		if (!(node->flags & LPM_TREE_NODE_FLAG_IM)) {
+			if (flags == BPF_NOEXIST) {
+				ret = -EEXIST;
+				goto out;
+			}
+			trie->n_entries--;
+		} else if (flags == BPF_EXIST) {
+			ret = -ENOENT;
+			goto out;
+		}
+
 		new_node->child[0] = node->child[0];
 		new_node->child[1] = node->child[1];
 
-		if (!(node->flags & LPM_TREE_NODE_FLAG_IM))
-			trie->n_entries--;
-
 		rcu_assign_pointer(*slot, new_node);
 		kfree_rcu(node, rcu);
 
 		goto out;
 	}
 
+	if (flags == BPF_EXIST) {
+		ret = -ENOENT;
+		goto out;
+	}
+
 	/* If the new node matches the prefix completely, it must be inserted
 	 * as an ancestor. Simply insert it between @node and *@slot.
 	 */