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bpf: sockmap: initialize sg table entries properly

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When CONFIG_DEBUG_SG is set, sg->sg_magic is initialized in
sg_init_table() and it is verified in sg api while navigating. We hit
BUG_ON when magic check is failed.

In functions sg_tcp_sendpage and sg_tcp_sendmsg, the struct containing
the scatterlist is already zeroed out. So to avoid extra memset, we
use sg_init_marker() to initialize sg_magic.

Fixed following things:
- In bpf_tcp_sendpage: initialize sg using sg_init_marker
- In bpf_tcp_sendmsg: Replace sg_init_table with sg_init_marker
- In bpf_tcp_push: Replace memset with sg_init_table where consumed
  sg entry needs to be re-initialized.

Signed-off-by: Prashant Bhole <bhole_prashant_q7@lab.ntt.co.jp>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Prashant Bhole 2018-03-30 09:21:00 +09:00 committed by Daniel Borkmann
parent f385178679
commit 6ef6d84cee
1 changed files with 8 additions and 5 deletions
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13
kernel/bpf/sockmap.c
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@ -341,7 +341,7 @@ retry:
md->sg_start++;
if (md->sg_start == MAX_SKB_FRAGS)
md->sg_start = 0;
memset(sg, 0, sizeof(*sg));
sg_init_table(sg, 1);
if (md->sg_start == md->sg_end)
break;
@ -843,7 +843,7 @@ static int bpf_tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size)
}
sg = md.sg_data;
sg_init_table(sg, MAX_SKB_FRAGS);
sg_init_marker(sg, MAX_SKB_FRAGS);
rcu_read_unlock();
lock_sock(sk);
@ -950,10 +950,14 @@ static int bpf_tcp_sendpage(struct sock *sk, struct page *page,
lock_sock(sk);
if (psock->cork_bytes)
if (psock->cork_bytes) {
m = psock->cork;
else
sg = &m->sg_data[m->sg_end];
} else {
m = &md;
sg = m->sg_data;
sg_init_marker(sg, MAX_SKB_FRAGS);
}
/* Catch case where ring is full and sendpage is stalled. */
if (unlikely(m->sg_end == m->sg_start &&
@ -961,7 +965,6 @@ static int bpf_tcp_sendpage(struct sock *sk, struct page *page,
goto out_err;
psock->sg_size += size;
sg = &m->sg_data[m->sg_end];
sg_set_page(sg, page, size, offset);
get_page(page);
m->sg_copy[m->sg_end] = true;