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bpf, sockmap: Fix memleak on ingress msg enqueue 

If backlog handler is running during a tear down operation we may enqueue
data on the ingress msg queue while tear down is trying to free it.

 sk_psock_backlog()
   sk_psock_handle_skb()
     skb_psock_skb_ingress()
       sk_psock_skb_ingress_enqueue()
         sk_psock_queue_msg(psock,msg)
                                           spin_lock(ingress_lock)
                                            sk_psock_zap_ingress()
                                             _sk_psock_purge_ingerss_msg()
                                              _sk_psock_purge_ingress_msg()
                                            -- free ingress_msg list --
                                           spin_unlock(ingress_lock)
           spin_lock(ingress_lock)
           list_add_tail(msg,ingress_msg) <- entry on list with no one
                                             left to free it.
           spin_unlock(ingress_lock)

To fix we only enqueue from backlog if the ENABLED bit is set. The tear
down logic clears the bit with ingress_lock set so we wont enqueue the
msg in the last step.

Fixes: 799aa7f98d ("skmsg: Avoid lock_sock() in sk_psock_backlog()")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210727160500.1713554-4-john.fastabend@gmail.com
This commit is contained in:
John Fastabend 2021-07-27 09:05:00 -07:00 committed by Andrii Nakryiko
parent 476d98018f
commit 9635720b7c
2 changed files with 35 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
include/linux/skmsg.h
View File

@ -285,11 +285,45 @@ static inline struct sk_psock *sk_psock(const struct sock *sk)
return rcu_dereference_sk_user_data(sk);
}
static inline void sk_psock_set_state(struct sk_psock *psock,
enum sk_psock_state_bits bit)
{
set_bit(bit, &psock->state);
}
static inline void sk_psock_clear_state(struct sk_psock *psock,
enum sk_psock_state_bits bit)
{
clear_bit(bit, &psock->state);
}
static inline bool sk_psock_test_state(const struct sk_psock *psock,
enum sk_psock_state_bits bit)
{
return test_bit(bit, &psock->state);
}
static inline void sock_drop(struct sock *sk, struct sk_buff *skb)
{
sk_drops_add(sk, skb);
kfree_skb(skb);
}
static inline void drop_sk_msg(struct sk_psock *psock, struct sk_msg *msg)
{
if (msg->skb)
sock_drop(psock->sk, msg->skb);
kfree(msg);
}
static inline void sk_psock_queue_msg(struct sk_psock *psock,
struct sk_msg *msg)
{
spin_lock_bh(&psock->ingress_lock);
list_add_tail(&msg->list, &psock->ingress_msg);
if (sk_psock_test_state(psock, SK_PSOCK_TX_ENABLED))
list_add_tail(&msg->list, &psock->ingress_msg);
else
drop_sk_msg(psock, msg);
spin_unlock_bh(&psock->ingress_lock);
}
@ -406,24 +440,6 @@ static inline void sk_psock_restore_proto(struct sock *sk,
psock->psock_update_sk_prot(sk, psock, true);
}
static inline void sk_psock_set_state(struct sk_psock *psock,
enum sk_psock_state_bits bit)
{
set_bit(bit, &psock->state);
}
static inline void sk_psock_clear_state(struct sk_psock *psock,
enum sk_psock_state_bits bit)
{
clear_bit(bit, &psock->state);
}
static inline bool sk_psock_test_state(const struct sk_psock *psock,
enum sk_psock_state_bits bit)
{
return test_bit(bit, &psock->state);
}
static inline struct sk_psock *sk_psock_get(struct sock *sk)
{
struct sk_psock *psock;

6
net/core/skmsg.c
View File

@ -584,12 +584,6 @@ static int sk_psock_handle_skb(struct sk_psock *psock, struct sk_buff *skb,
return sk_psock_skb_ingress(psock, skb);
}
static void sock_drop(struct sock *sk, struct sk_buff *skb)
{
sk_drops_add(sk, skb);
kfree_skb(skb);
}
static void sk_psock_skb_state(struct sk_psock *psock,
struct sk_psock_work_state *state,
struct sk_buff *skb,