From: Mukesh Kacker <mukesh.kac...@oracle.com> rds_send_queue_rm() allows for the "current datagram" being queued to exceed SO_SNDBUF thresholds by checking bytes queued without counting in length of current datagram. (Since sk_sndbuf is set to twice requested SO_SNDBUF value as a kernel heuristic this is usually fine!)
If this "current datagram" squeezing past the threshold is itself many times the size of the sk_sndbuf threshold itself then even twice the SO_SNDBUF does not save us and it gets queued but cannot be transmitted. Threads block and deadlock and device becomes unusable. The check for this datagram not exceeding SNDBUF thresholds (EMSGSIZE) is not done on this datagram as that check is only done if queueing attempt fails. (Datagrams that follow this datagram fail queueing attempts, go through the check and eventually trip EMSGSIZE error but zero length datagrams silently fail!) This fix moves the check for datagrams exceeding SNDBUF limits before any processing or queueing is attempted and returns EMSGSIZE early in the rds_sndmsg() code. This change also ensures that all datagrams get checked for exceeding SNDBUF/sk_sndbuf size limits and the large datagrams that exceed those limits do not get to rds_send_queue_rm() code for processing. Signed-off-by: Mukesh Kacker <mukesh.kac...@oracle.com> Signed-off-by: Santosh Shilimkar <ssant...@kernel.org> Signed-off-by: Santosh Shilimkar <santosh.shilim...@oracle.com> --- net/rds/send.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/net/rds/send.c b/net/rds/send.c index b0fe412..c2667bf 100644 --- a/net/rds/send.c +++ b/net/rds/send.c @@ -1015,6 +1015,11 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len) goto out; } + if (payload_len > rds_sk_sndbuf(rs)) { + ret = -EMSGSIZE; + goto out; + } + /* size of rm including all sgs */ ret = rds_rm_size(msg, payload_len); if (ret < 0) @@ -1086,11 +1091,7 @@ int rds_sendmsg(struct socket *sock, struct msghdr *msg, size_t payload_len) while (!rds_send_queue_rm(rs, conn, rm, rs->rs_bound_port, dport, &queued)) { rds_stats_inc(s_send_queue_full); - /* XXX make sure this is reasonable */ - if (payload_len > rds_sk_sndbuf(rs)) { - ret = -EMSGSIZE; - goto out; - } + if (nonblock) { ret = -EAGAIN; goto out; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html