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Message-ID: <d6294506-75a8-4a23-aa98-65b719c1d368@web.de>
Date: Sat, 30 Dec 2023 21:14:13 +0100
From: Markus Elfring <Markus.Elfring@....de>
To: bpf@...r.kernel.org, netdev@...r.kernel.org,
kernel-janitors@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
Andrii Nakryiko <andrii@...nel.org>, Daniel Borkmann <daniel@...earbox.net>,
Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
Martin KaFai Lau <martin.lau@...ux.dev>, Song Liu <song@...nel.org>,
Stanislav Fomichev <sdf@...gle.com>, Yonghong Song <yonghong.song@...ux.dev>
Cc: LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 5/5] bpf: Improve exception handling in trie_update_elem()
From: Markus Elfring <elfring@...rs.sourceforge.net>
Date: Sat, 30 Dec 2023 20:28:11 +0100
The kfree() function was called in some cases by
the trie_update_elem() function during error handling
even if the passed variable contained a null pointer.
This issue was detected by using the Coccinelle software.
* Thus adjust jump targets.
* Reorder data processing steps at the end.
* Delete an initialisation (for the variable “new_node”)
and a repeated pointer check which became unnecessary
with this refactoring.
Signed-off-by: Markus Elfring <elfring@...rs.sourceforge.net>
---
kernel/bpf/lpm_trie.c | 24 +++++++++++-------------
1 file changed, 11 insertions(+), 13 deletions(-)
diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index b32be680da6c..6c372d831d0f 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -307,7 +307,7 @@ static long trie_update_elem(struct bpf_map *map,
void *_key, void *value, u64 flags)
{
struct lpm_trie *trie = container_of(map, struct lpm_trie, map);
- struct lpm_trie_node *node, *im_node = NULL, *new_node = NULL;
+ struct lpm_trie_node *node, *im_node = NULL, *new_node;
struct lpm_trie_node __rcu **slot;
struct bpf_lpm_trie_key *key = _key;
unsigned long irq_flags;
@@ -327,13 +327,13 @@ static long trie_update_elem(struct bpf_map *map,
if (trie->n_entries == trie->map.max_entries) {
ret = -ENOSPC;
- goto out;
+ goto unlock;
}
new_node = lpm_trie_node_alloc(trie, value);
if (!new_node) {
ret = -ENOMEM;
- goto out;
+ goto unlock;
}
trie->n_entries++;
@@ -368,7 +368,7 @@ static long trie_update_elem(struct bpf_map *map,
*/
if (!node) {
rcu_assign_pointer(*slot, new_node);
- goto out;
+ goto decrement_counter;
}
/* If the slot we picked already exists, replace it with @new_node
@@ -384,7 +384,7 @@ static long trie_update_elem(struct bpf_map *map,
rcu_assign_pointer(*slot, new_node);
kfree_rcu(node, rcu);
- goto out;
+ goto decrement_counter;
}
/* If the new node matches the prefix completely, it must be inserted
@@ -394,13 +394,13 @@ static long trie_update_elem(struct bpf_map *map,
next_bit = extract_bit(node->data, matchlen);
rcu_assign_pointer(new_node->child[next_bit], node);
rcu_assign_pointer(*slot, new_node);
- goto out;
+ goto decrement_counter;
}
im_node = lpm_trie_node_alloc(trie, NULL);
if (!im_node) {
ret = -ENOMEM;
- goto out;
+ goto decrement_counter;
}
im_node->prefixlen = matchlen;
@@ -419,15 +419,13 @@ static long trie_update_elem(struct bpf_map *map,
/* Finally, assign the intermediate node to the determined slot */
rcu_assign_pointer(*slot, im_node);
-out:
if (ret) {
- if (new_node)
- trie->n_entries--;
-
- kfree(new_node);
kfree(im_node);
+decrement_counter:
+ trie->n_entries--;
+ kfree(new_node);
}
-
+unlock:
spin_unlock_irqrestore(&trie->lock, irq_flags);
return ret;
--
2.43.0
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