From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Grover Subject: [PATCH 2/5] RDS: Fix potential race around rds_i[bw]_allocation Date: Fri, 30 Oct 2009 11:51:54 -0700 Message-ID: <1256928717-17757-2-git-send-email-andy.grover@oracle.com> References: <1256928717-17757-1-git-send-email-andy.grover@oracle.com> Cc: rds-devel@oss.oracle.com To: netdev@vger.kernel.org Return-path: Received: from acsinet12.oracle.com ([141.146.126.234]:55991 "EHLO acsinet12.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757316AbZJ3SxS (ORCPT ); Fri, 30 Oct 2009 14:53:18 -0400 Received: from rgminet13.oracle.com (rcsinet13.oracle.com [148.87.113.125]) by acsinet12.oracle.com (Switch-3.3.1/Switch-3.3.1) with ESMTP id n9UIr9a9012332 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Fri, 30 Oct 2009 18:53:11 GMT In-Reply-To: <1256928717-17757-1-git-send-email-andy.grover@oracle.com> Sender: netdev-owner@vger.kernel.org List-ID: >>From Shin Hong: "At rds_ib_recv_refill_one(), it first executes atomic_read(&rds_ib_allocation) for if-condition checking, and then executes atomic_inc(&rds_ib_allocation) if the condition was not satisfied. However, if any other code which updates rds_ib_allocation executes between these two atomic operation executions, it seems that it may result race condition. (especially when rds_ib_allocation + 1 == rds_ib_sysctl_max_recv_allocation)" This patch fixes this by using atomic_inc_unless to eliminate the possibility of allocating more than rds_ib_sysctl_max_recv_allocation and then decrementing the count if the allocation fails. It also makes an identical change to the iwarp transport. Reported-by: Shin Hong Signed-off-by: Andy Grover --- net/rds/ib_recv.c | 7 ++++--- net/rds/iw_recv.c | 7 ++++--- 2 files changed, 8 insertions(+), 6 deletions(-) diff --git a/net/rds/ib_recv.c b/net/rds/ib_recv.c index cd7a6cf..2f009d3 100644 --- a/net/rds/ib_recv.c +++ b/net/rds/ib_recv.c @@ -143,15 +143,16 @@ static int rds_ib_recv_refill_one(struct rds_connection *conn, int ret = -ENOMEM; if (recv->r_ibinc == NULL) { - if (atomic_read(&rds_ib_allocation) >= rds_ib_sysctl_max_recv_allocation) { + if (!atomic_add_unless(&rds_ib_allocation, 1, rds_ib_sysctl_max_recv_allocation)) { rds_ib_stats_inc(s_ib_rx_alloc_limit); goto out; } recv->r_ibinc = kmem_cache_alloc(rds_ib_incoming_slab, kptr_gfp); - if (recv->r_ibinc == NULL) + if (recv->r_ibinc == NULL) { + atomic_dec(&rds_ib_allocation); goto out; - atomic_inc(&rds_ib_allocation); + } INIT_LIST_HEAD(&recv->r_ibinc->ii_frags); rds_inc_init(&recv->r_ibinc->ii_inc, conn, conn->c_faddr); } diff --git a/net/rds/iw_recv.c b/net/rds/iw_recv.c index 8683f5f..9f98150 100644 --- a/net/rds/iw_recv.c +++ b/net/rds/iw_recv.c @@ -143,15 +143,16 @@ static int rds_iw_recv_refill_one(struct rds_connection *conn, int ret = -ENOMEM; if (recv->r_iwinc == NULL) { - if (atomic_read(&rds_iw_allocation) >= rds_iw_sysctl_max_recv_allocation) { + if (!atomic_add_unless(&rds_iw_allocation, 1, rds_iw_sysctl_max_recv_allocation)) { rds_iw_stats_inc(s_iw_rx_alloc_limit); goto out; } recv->r_iwinc = kmem_cache_alloc(rds_iw_incoming_slab, kptr_gfp); - if (recv->r_iwinc == NULL) + if (recv->r_iwinc == NULL) { + atomic_dec(&rds_iw_allocation); goto out; - atomic_inc(&rds_iw_allocation); + } INIT_LIST_HEAD(&recv->r_iwinc->ii_frags); rds_inc_init(&recv->r_iwinc->ii_inc, conn, conn->c_faddr); } -- 1.6.3.3