From abaeb096ca38cad02c8a68c49ddd7efc043c319a Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Wed, 2 May 2018 13:50:29 -0700 Subject: [PATCH] bpf: sockmap, fix error handling in redirect failures When a redirect failure happens we release the buffers in-flight without calling a sk_mem_uncharge(), the uncharge is called before dropping the sock lock for the redirecte, however we missed updating the ring start index. When no apply actions are in progress this is OK because we uncharge the entire buffer before the redirect. But, when we have apply logic running its possible that only a portion of the buffer is being redirected. In this case we only do memory accounting for the buffer slice being redirected and expect to be able to loop over the BPF program again and/or if a sock is closed uncharge the memory at sock destruct time. With an invalid start index however the program logic looks at the start pointer index, checks the length, and when seeing the length is zero (from the initial release and failure to update the pointer) aborts without uncharging/releasing the remaining memory. The fix for this is simply to update the start index. To avoid fixing this error in two locations we do a small refactor and remove one case where it is open-coded. Then fix it in the single function. Signed-off-by: John Fastabend Signed-off-by: Alexei Starovoitov --- kernel/bpf/sockmap.c | 28 ++++++++++++---------------- 1 file changed, 12 insertions(+), 16 deletions(-) diff --git a/kernel/bpf/sockmap.c b/kernel/bpf/sockmap.c index 052c313b12db..098eca568c2b 100644 --- a/kernel/bpf/sockmap.c +++ b/kernel/bpf/sockmap.c @@ -393,7 +393,8 @@ static void return_mem_sg(struct sock *sk, int bytes, struct sk_msg_buff *md) } while (i != md->sg_end); } -static void free_bytes_sg(struct sock *sk, int bytes, struct sk_msg_buff *md) +static void free_bytes_sg(struct sock *sk, int bytes, + struct sk_msg_buff *md, bool charge) { struct scatterlist *sg = md->sg_data; int i = md->sg_start, free; @@ -403,11 +404,13 @@ static void free_bytes_sg(struct sock *sk, int bytes, struct sk_msg_buff *md) if (bytes < free) { sg[i].length -= bytes; sg[i].offset += bytes; - sk_mem_uncharge(sk, bytes); + if (charge) + sk_mem_uncharge(sk, bytes); break; } - sk_mem_uncharge(sk, sg[i].length); + if (charge) + sk_mem_uncharge(sk, sg[i].length); put_page(sg_page(&sg[i])); bytes -= sg[i].length; sg[i].length = 0; @@ -418,6 +421,7 @@ static void free_bytes_sg(struct sock *sk, int bytes, struct sk_msg_buff *md) if (i == MAX_SKB_FRAGS) i = 0; } + md->sg_start = i; } static int free_sg(struct sock *sk, int start, struct sk_msg_buff *md) @@ -576,10 +580,10 @@ static int bpf_tcp_sendmsg_do_redirect(struct sock *sk, int send, struct sk_msg_buff *md, int flags) { + bool ingress = !!(md->flags & BPF_F_INGRESS); struct smap_psock *psock; struct scatterlist *sg; - int i, err, free = 0; - bool ingress = !!(md->flags & BPF_F_INGRESS); + int err = 0; sg = md->sg_data; @@ -607,16 +611,8 @@ static int bpf_tcp_sendmsg_do_redirect(struct sock *sk, int send, out_rcu: rcu_read_unlock(); out: - i = md->sg_start; - while (sg[i].length) { - free += sg[i].length; - put_page(sg_page(&sg[i])); - sg[i].length = 0; - i++; - if (i == MAX_SKB_FRAGS) - i = 0; - } - return free; + free_bytes_sg(NULL, send, md, false); + return err; } static inline void bpf_md_init(struct smap_psock *psock) @@ -720,7 +716,7 @@ more_data: break; case __SK_DROP: default: - free_bytes_sg(sk, send, m); + free_bytes_sg(sk, send, m, true); apply_bytes_dec(psock, send); *copied -= send; psock->sg_size -= send; -- 2.30.2