diff options
| -rw-r--r-- | net/netlink/af_netlink.c | 34 |
1 files changed, 22 insertions, 12 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 8f060d7f9a0e..0a49a8c7c564 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -2785,6 +2785,7 @@ static int netlink_dump(struct sock *sk) struct sk_buff *skb = NULL; struct nlmsghdr *nlh; int len, err = -ENOBUFS; + int alloc_min_size; int alloc_size; mutex_lock(nlk->cb_mutex); @@ -2793,9 +2794,6 @@ static int netlink_dump(struct sock *sk) goto errout_skb; } - cb = &nlk->cb; - alloc_size = max_t(int, cb->min_dump_alloc, NLMSG_GOODSIZE); - if (!netlink_rx_is_mmaped(sk) && atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) goto errout_skb; @@ -2805,23 +2803,35 @@ static int netlink_dump(struct sock *sk) * to reduce number of system calls on dump operations, if user * ever provided a big enough buffer. */ - if (alloc_size < nlk->max_recvmsg_len) { - skb = netlink_alloc_skb(sk, - nlk->max_recvmsg_len, - nlk->portid, + cb = &nlk->cb; + alloc_min_size = max_t(int, cb->min_dump_alloc, NLMSG_GOODSIZE); + + if (alloc_min_size < nlk->max_recvmsg_len) { + alloc_size = nlk->max_recvmsg_len; + skb = netlink_alloc_skb(sk, alloc_size, nlk->portid, GFP_KERNEL | __GFP_NOWARN | __GFP_NORETRY); - /* available room should be exact amount to avoid MSG_TRUNC */ - if (skb) - skb_reserve(skb, skb_tailroom(skb) - - nlk->max_recvmsg_len); } - if (!skb) + if (!skb) { + alloc_size = alloc_min_size; skb = netlink_alloc_skb(sk, alloc_size, nlk->portid, GFP_KERNEL); + } if (!skb) goto errout_skb; + + /* Trim skb to allocated size. User is expected to provide buffer as + * large as max(min_dump_alloc, 16KiB (mac_recvmsg_len capped at + * netlink_recvmsg())). dump will pack as many smaller messages as + * could fit within the allocated skb. skb is typically allocated + * with larger space than required (could be as much as near 2x the + * requested size with align to next power of 2 approach). Allowing + * dump to use the excess space makes it difficult for a user to have a + * reasonable static buffer based on the expected largest dump of a + * single netdev. The outcome is MSG_TRUNC error. + */ + skb_reserve(skb, skb_tailroom(skb) - alloc_size); netlink_skb_set_owner_r(skb, sk); len = cb->dump(skb, cb); |