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bpf: skmsg, fix potential psock NULL pointer dereference

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Report from Dan Carpenter,

 net/core/skmsg.c:792 sk_psock_write_space()
 error: we previously assumed 'psock' could be null (see line 790)

 net/core/skmsg.c
   789 psock = sk_psock(sk);
   790 if (likely(psock && sk_psock_test_state(psock, SK_PSOCK_TX_ENABLED)))
 Check for NULL
   791 schedule_work(&psock->work);
   792 write_space = psock->saved_write_space;
                     ^^^^^^^^^^^^^^^^^^^^^^^^
   793          rcu_read_unlock();
   794          write_space(sk);

Ensure psock dereference on line 792 only occurs if psock is not null.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Fixes: 604326b41a ("bpf, sockmap: convert to generic sk_msg interface")
Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
John Fastabend 2019-11-21 08:25:09 -08:00 committed by David S. Miller
parent 7599a896f2
commit 8163999db4
1 changed files with 8 additions and 5 deletions
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13
net/core/skmsg.c
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@ -793,15 +793,18 @@ static void sk_psock_strp_data_ready(struct sock *sk)
static void sk_psock_write_space(struct sock *sk) static void sk_psock_write_space(struct sock *sk)
{ {
struct sk_psock *psock; struct sk_psock *psock;
void (*write_space)(struct sock *sk); void (*write_space)(struct sock *sk) = NULL;
rcu_read_lock(); rcu_read_lock();
psock = sk_psock(sk); psock = sk_psock(sk);
if (likely(psock && sk_psock_test_state(psock, SK_PSOCK_TX_ENABLED))) if (likely(psock)) {
schedule_work(&psock->work); if (sk_psock_test_state(psock, SK_PSOCK_TX_ENABLED))
write_space = psock->saved_write_space; schedule_work(&psock->work);
write_space = psock->saved_write_space;
}
rcu_read_unlock(); rcu_read_unlock();
write_space(sk); if (write_space)
write_space(sk);
} }
int sk_psock_init_strp(struct sock *sk, struct sk_psock *psock) int sk_psock_init_strp(struct sock *sk, struct sk_psock *psock)