xfrm: state: use a consistent pcpu_id in xfrm_state_find

If we get preempted during xfrm_state_find, we could run
xfrm_state_look_at using a different pcpu_id than the one
xfrm_state_find saw. This could lead to ignoring states that should
have matched, and triggering acquires on a CPU that already has a pcpu
state.

    xfrm_state_find starts on CPU1
    pcpu_id = 1
    lookup starts
    <preemption, we're now on CPU2>
    xfrm_state_look_at pcpu_id = 2
       finds a state
found:
    best->pcpu_num != pcpu_id (2 != 1)
    if (!x && !error && !acquire_in_progress) {
        ...
        xfrm_state_alloc
        xfrm_init_tempstate
        ...

This can be avoided by passing the original pcpu_id down to all
xfrm_state_look_at() calls.

Also switch to raw_smp_processor_id, disabling preempting just to
re-enable it immediately doesn't really make sense.

Fixes: 1ddf9916ac09 ("xfrm: Add support for per cpu xfrm state handling.")
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index 2e2e95d2a06fce6592feabe26d3a284ec17ed5ad..7e34fc94f668b2769a9d807f14fff6dfce1ee7e4 100644 (file)
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -1307,14 +1307,8 @@ static void xfrm_hash_grow_check(struct net *net, int have_hash_collision)
 static void xfrm_state_look_at(struct xfrm_policy *pol, struct xfrm_state *x,
                               const struct flowi *fl, unsigned short family,
                               struct xfrm_state **best, int *acq_in_progress,
-                              int *error)
+                              int *error, unsigned int pcpu_id)
 {
-       /* We need the cpu id just as a lookup key,
-        * we don't require it to be stable.
-        */
-       unsigned int pcpu_id = get_cpu();
-       put_cpu();
-
        /* Resolution logic:
         * 1. There is a valid state with matching selector. Done.
         * 2. Valid state with inappropriate selector. Skip.
@@ -1381,8 +1375,7 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr,
        /* We need the cpu id just as a lookup key,
         * we don't require it to be stable.
         */
-       pcpu_id = get_cpu();
-       put_cpu();
+       pcpu_id = raw_smp_processor_id();
 
        to_put = NULL;
 
@@ -1402,7 +1395,7 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr,
                    tmpl->id.proto == x->id.proto &&
                    (tmpl->id.spi == x->id.spi || !tmpl->id.spi))
                        xfrm_state_look_at(pol, x, fl, encap_family,
-                                          &best, &acquire_in_progress, &error);
+                                          &best, &acquire_in_progress, &error, pcpu_id);
        }
 
        if (best)
@@ -1419,7 +1412,7 @@ xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr,
                    tmpl->id.proto == x->id.proto &&
                    (tmpl->id.spi == x->id.spi || !tmpl->id.spi))
                        xfrm_state_look_at(pol, x, fl, family,
-                                          &best, &acquire_in_progress, &error);
+                                          &best, &acquire_in_progress, &error, pcpu_id);
        }
 
 cached:
@@ -1460,7 +1453,7 @@ cached:
                    tmpl->id.proto == x->id.proto &&
                    (tmpl->id.spi == x->id.spi || !tmpl->id.spi))
                        xfrm_state_look_at(pol, x, fl, family,
-                                          &best, &acquire_in_progress, &error);
+                                          &best, &acquire_in_progress, &error, pcpu_id);
        }
        if (best || acquire_in_progress)
                goto found;
@@ -1495,7 +1488,7 @@ cached:
                    tmpl->id.proto == x->id.proto &&
                    (tmpl->id.spi == x->id.spi || !tmpl->id.spi))
                        xfrm_state_look_at(pol, x, fl, family,
-                                          &best, &acquire_in_progress, &error);
+                                          &best, &acquire_in_progress, &error, pcpu_id);
        }
 
 found: