RDS: Fix potential race around rds_i[bw]_allocation
"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 <hongshin@gmail.com>
Signed-off-by: Andy Grover <andy.grover@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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 @@
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);
}