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authorFlorian Westphal <fw@strlen.de>2016-08-09 13:16:07 +0300
committerSteffen Klassert <steffen.klassert@secunet.com>2016-08-10 12:23:24 +0300
commitb65e3d7be06fd8ff5236439254f338fe1a8d4bbd (patch)
treee9831de71641f57f8987811bdfd8b74b9cdbb438 /net/xfrm/xfrm_state.c
parentdf7274eb70b7c8488170ebe8757dd94647a8e1e5 (diff)
downloadlinux-b65e3d7be06fd8ff5236439254f338fe1a8d4bbd.tar.xz
xfrm: state: add sequence count to detect hash resizes
Once xfrm_state_find is lockless we have to cope with a concurrent resize opertion. We use a sequence counter to block in case a resize is in progress and to detect if we might have missed a state that got moved to a new hash table. Signed-off-by: Florian Westphal <fw@strlen.de> Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Diffstat (limited to 'net/xfrm/xfrm_state.c')
-rw-r--r--net/xfrm/xfrm_state.c15
1 files changed, 15 insertions, 0 deletions
diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 8e373876924f..ac4037cf6a29 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -36,6 +36,7 @@
*/
static unsigned int xfrm_state_hashmax __read_mostly = 1 * 1024 * 1024;
+static __read_mostly seqcount_t xfrm_state_hash_generation = SEQCNT_ZERO(xfrm_state_hash_generation);
static inline bool xfrm_state_hold_rcu(struct xfrm_state __rcu *x)
{
@@ -127,6 +128,7 @@ static void xfrm_hash_resize(struct work_struct *work)
}
spin_lock_bh(&net->xfrm.xfrm_state_lock);
+ write_seqcount_begin(&xfrm_state_hash_generation);
nhashmask = (nsize / sizeof(struct hlist_head)) - 1U;
for (i = net->xfrm.state_hmask; i >= 0; i--)
@@ -143,6 +145,7 @@ static void xfrm_hash_resize(struct work_struct *work)
net->xfrm.state_byspi = nspi;
net->xfrm.state_hmask = nhashmask;
+ write_seqcount_end(&xfrm_state_hash_generation);
spin_unlock_bh(&net->xfrm.xfrm_state_lock);
osize = (ohashmask + 1) * sizeof(struct hlist_head);
@@ -787,10 +790,13 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr,
struct xfrm_state *best = NULL;
u32 mark = pol->mark.v & pol->mark.m;
unsigned short encap_family = tmpl->encap_family;
+ unsigned int sequence;
struct km_event c;
to_put = NULL;
+ sequence = read_seqcount_begin(&xfrm_state_hash_generation);
+
spin_lock_bh(&net->xfrm.xfrm_state_lock);
h = xfrm_dst_hash(net, daddr, saddr, tmpl->reqid, encap_family);
hlist_for_each_entry_rcu(x, net->xfrm.state_bydst + h, bydst) {
@@ -894,6 +900,15 @@ out:
spin_unlock_bh(&net->xfrm.xfrm_state_lock);
if (to_put)
xfrm_state_put(to_put);
+
+ if (read_seqcount_retry(&xfrm_state_hash_generation, sequence)) {
+ *err = -EAGAIN;
+ if (x) {
+ xfrm_state_put(x);
+ x = NULL;
+ }
+ }
+
return x;
}