| From | Kamal Mostafa <> | Subject | [PATCH 3.19.y-ckt 093/155] net: add pfmemalloc check in sk_add_backlog() | Date | Thu, 12 Nov 2015 15:17:27 -0800 |
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3.19.8-ckt10 -stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet <edumazet@google.com>
[ Upstream commit c7c49b8fde26b74277188bdc6c9dca38db6fa35b ]
Greg reported crashes hitting the following check in __sk_backlog_rcv()
BUG_ON(!sock_flag(sk, SOCK_MEMALLOC));
The pfmemalloc bit is currently checked in sk_filter().
This works correctly for TCP, because sk_filter() is ran in tcp_v[46]_rcv() before hitting the prequeue or backlog checks.
For UDP or other protocols, this does not work, because the sk_filter() is ran from sock_queue_rcv_skb(), which might be called _after_ backlog queuing if socket is owned by user by the time packet is processed by softirq handler.
Fixes: b4b9e35585089 ("netvm: set PF_MEMALLOC as appropriate during SKB processing") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: Greg Thelen <gthelen@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- include/net/sock.h | 8 ++++++++ 1 file changed, 8 insertions(+)
diff --git a/include/net/sock.h b/include/net/sock.h index 45b54d3..173743e 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -825,6 +825,14 @@ static inline __must_check int sk_add_backlog(struct sock *sk, struct sk_buff *s if (sk_rcvqueues_full(sk, limit)) return -ENOBUFS; + /* + * If the skb was allocated from pfmemalloc reserves, only + * allow SOCK_MEMALLOC sockets to use it as this socket is + * helping free memory + */ + if (skb_pfmemalloc(skb) && !sock_flag(sk, SOCK_MEMALLOC)) + return -ENOMEM; + __sk_add_backlog(sk, skb); sk->sk_backlog.len += skb->truesize; return 0; -- 1.9.1
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