[PATCH v2 bpf-next 2/2] bpf: sockmap: initialize sg table entries properly
From: Prashant Bhole <hidden>
Date: 2018-03-30 00:22:50
Subsystem:
bpf [general] (safe dynamic programs and tools), the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, Linus Torvalds
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 <redacted> --- kernel/bpf/sockmap.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c
index 69c5bccabd22..b4f01656c452 100644
--- a/kernel/bpf/sockmap.c
+++ b/kernel/bpf/sockmap.c@@ -312,7 +312,7 @@ static int bpf_tcp_push(struct sock *sk, int apply_bytes, 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;
@@ -656,7 +656,7 @@ 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);
@@ -763,10 +763,14 @@ 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 &&
@@ -774,7 +778,6 @@ 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;
--
2.14.3