From: Sabrina Dubroca 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 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 Reviewed-by: Florian Westphal Signed-off-by: Steffen Klassert --- net/xfrm/xfrm_state.c | 19 ++++++------------- 1 file changed, 6 insertions(+), 13 deletions(-) diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c index 2e2e95d2a06f..7e34fc94f668 100644 --- 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 @@ 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); } if (best || acquire_in_progress) goto found; @@ -1495,7 +1488,7 @@ 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); } found: -- 2.43.0