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bpf, sockmap: fix use-after-free when the stream parser resizes the skb #8010

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bpf, sockmap: fix use-after-free when the stream parser resizes the skb #8010

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26 changes: 21 additions & 5 deletions net/core/skmsg.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1146,14 +1146,30 @@ static int sk_psock_strp_parse(struct strparser *strp, struct sk_buff *skb)
struct bpf_prog *prog;
int ret = skb->len;

rcu_read_lock();
guard(rcu)();
prog = READ_ONCE(psock->progs.stream_parser);
if (likely(prog)) {
skb->sk = psock->sk;
ret = bpf_prog_run_pin_on_cpu(prog, skb);
skb->sk = NULL;
struct sk_buff *parse_skb = skb;

/*
* strparser chains the message skbs through skb->frag_list and
* keeps a pointer into that list in strp->skb_nextp. The parser
* program may call bpf_skb_change_tail() and friends, which go
* through __pskb_pull_tail() and free the frag_list skbs that
* strparser still tracks. Run the program on a clone when a
* frag_list is present so it cannot drop frags strparser owns.
*/
if (skb_has_frag_list(skb)) {
parse_skb = skb_clone(skb, GFP_ATOMIC);
if (!parse_skb)
return -ENOMEM;
}
parse_skb->sk = psock->sk;
ret = bpf_prog_run_pin_on_cpu(prog, parse_skb);
parse_skb->sk = NULL;
if (parse_skb != skb)
kfree_skb(parse_skb);
}
rcu_read_unlock();
return ret;
}

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