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bpf: Fix NULL pointer dereference in bpf_sk_storage_clone and diag paths

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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:
  <IRQ>
  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: 5d800f87d0 ("bpf: Support lockless unlink when freeing map or local storage")
Reported-by: Xiang Mei <xmei5@asu.edu>
Acked-by: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20260422065411.1007737-2-bestswngs@gmail.com
This commit is contained in:
Weiming Shi 2026-04-21 23:54:12 -07:00 committed by Martin KaFai Lau
parent cd0eb48b38
commit 375e4e33c1
1 changed files with 7 additions and 6 deletions
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13
net/core/bpf_sk_storage.c
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@ -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;
}