From 375e4e33c18dfa05c5dfd5f3dfffeb29343dd4c7 Mon Sep 17 00:00:00 2001 From: Weiming Shi Date: Tue, 21 Apr 2026 23:54:12 -0700 Subject: [PATCH] bpf: Fix NULL pointer dereference in bpf_sk_storage_clone and diag paths bpf_selem_unlink_nofail() sets SDATA(selem)->smap to NULL before removing the selem from the storage hlist. A concurrent RCU reader in bpf_sk_storage_clone() can observe the selem still on the list with smap already NULL, causing a NULL pointer dereference. general protection fault, probably for non-canonical address 0xdffffc000000000a: KASAN: null-ptr-deref in range [0x0000000000000050-0x0000000000000057] RIP: 0010:bpf_sk_storage_clone+0x1cd/0xaa0 net/core/bpf_sk_storage.c:174 Call Trace: sk_clone+0xfed/0x1980 net/core/sock.c:2591 inet_csk_clone_lock+0x30/0x760 net/ipv4/inet_connection_sock.c:1222 tcp_create_openreq_child+0x35/0x2680 net/ipv4/tcp_minisocks.c:571 tcp_v4_syn_recv_sock+0x123/0xf90 net/ipv4/tcp_ipv4.c:1729 tcp_check_req+0x8e1/0x2580 include/net/tcp.h:855 tcp_v4_rcv+0x1845/0x3b80 net/ipv4/tcp_ipv4.c:2347 Add a NULL check for smap in bpf_sk_storage_clone(). bpf_sk_storage_diag_put_all() has the same issue. Add a NULL check and pass the validated smap directly to diag_get(), which is refactored to take smap as a parameter instead of reading it internally. bpf_sk_storage_diag_put() uses diag->maps[i] which is always valid under its refcount, so diag->maps[i] is passed directly to diag_get(). Fixes: 5d800f87d0a5 ("bpf: Support lockless unlink when freeing map or local storage") Reported-by: Xiang Mei Acked-by: Amery Hung Signed-off-by: Weiming Shi Signed-off-by: Martin KaFai Lau Link: https://patch.msgid.link/20260422065411.1007737-2-bestswngs@gmail.com --- net/core/bpf_sk_storage.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/net/core/bpf_sk_storage.c b/net/core/bpf_sk_storage.c index 14eb7812bda4..dc3e8fce8809 100644 --- a/net/core/bpf_sk_storage.c +++ b/net/core/bpf_sk_storage.c @@ -172,7 +172,7 @@ int bpf_sk_storage_clone(const struct sock *sk, struct sock *newsk) struct bpf_map *map; smap = rcu_dereference(SDATA(selem)->smap); - if (!(smap->map.map_flags & BPF_F_CLONE)) + if (!smap || !(smap->map.map_flags & BPF_F_CLONE)) continue; /* Note that for lockless listeners adding new element @@ -531,10 +531,10 @@ bpf_sk_storage_diag_alloc(const struct nlattr *nla_stgs) } EXPORT_SYMBOL_GPL(bpf_sk_storage_diag_alloc); -static int diag_get(struct bpf_local_storage_data *sdata, struct sk_buff *skb) +static int diag_get(struct bpf_local_storage_map *smap, + struct bpf_local_storage_data *sdata, struct sk_buff *skb) { struct nlattr *nla_stg, *nla_value; - struct bpf_local_storage_map *smap; /* It cannot exceed max nlattr's payload */ BUILD_BUG_ON(U16_MAX - NLA_HDRLEN < BPF_LOCAL_STORAGE_MAX_VALUE_SIZE); @@ -543,7 +543,6 @@ static int diag_get(struct bpf_local_storage_data *sdata, struct sk_buff *skb) if (!nla_stg) return -EMSGSIZE; - smap = rcu_dereference(sdata->smap); if (nla_put_u32(skb, SK_DIAG_BPF_STORAGE_MAP_ID, smap->map.id)) goto errout; @@ -596,9 +595,11 @@ static int bpf_sk_storage_diag_put_all(struct sock *sk, struct sk_buff *skb, saved_len = skb->len; hlist_for_each_entry_rcu(selem, &sk_storage->list, snode) { smap = rcu_dereference(SDATA(selem)->smap); + if (!smap) + continue; diag_size += nla_value_size(smap->map.value_size); - if (nla_stgs && diag_get(SDATA(selem), skb)) + if (nla_stgs && diag_get(smap, SDATA(selem), skb)) /* Continue to learn diag_size */ err = -EMSGSIZE; } @@ -665,7 +666,7 @@ int bpf_sk_storage_diag_put(struct bpf_sk_storage_diag *diag, diag_size += nla_value_size(diag->maps[i]->value_size); - if (nla_stgs && diag_get(sdata, skb)) + if (nla_stgs && diag_get((struct bpf_local_storage_map *)diag->maps[i], sdata, skb)) /* Continue to learn diag_size */ err = -EMSGSIZE; }