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authorDavid Ahern <dsahern@gmail.com>2018-12-11 18:57:21 -0700
committerDavid S. Miller <davem@davemloft.net>2018-12-14 15:44:47 -0800
commit9c29a2f55ec05cc8b525ee3b2d75d3cd37911123 (patch)
tree39283a1e264ed4d46da436a5ec4b6c704392c5e8 /net/core/neighbour.c
parentnet_sched: fold tcf_block_cb_call() into tc_setup_cb_call() (diff)
downloadlinux-dev-9c29a2f55ec05cc8b525ee3b2d75d3cd37911123.tar.xz
linux-dev-9c29a2f55ec05cc8b525ee3b2d75d3cd37911123.zip
neighbor: Fix locking order for gc_list changes
Lock checker noted an inverted lock order between neigh_change_state (neighbor lock then table lock) and neigh_periodic_work (table lock and then neighbor lock) resulting in: [ 121.057652] ====================================================== [ 121.058740] WARNING: possible circular locking dependency detected [ 121.059861] 4.20.0-rc6+ #43 Not tainted [ 121.060546] ------------------------------------------------------ [ 121.061630] kworker/0:2/65 is trying to acquire lock: [ 121.062519] (____ptrval____) (&n->lock){++--}, at: neigh_periodic_work+0x237/0x324 [ 121.063894] [ 121.063894] but task is already holding lock: [ 121.064920] (____ptrval____) (&tbl->lock){+.-.}, at: neigh_periodic_work+0x194/0x324 [ 121.066274] [ 121.066274] which lock already depends on the new lock. [ 121.066274] [ 121.067693] [ 121.067693] the existing dependency chain (in reverse order) is: ... Fix by renaming neigh_change_state to neigh_update_gc_list, changing it to only manage whether an entry should be on the gc_list and taking locks in the same order as neigh_periodic_work. Invoke at the end of neigh_update only if diff between old or new states has the PERMANENT flag set. Fixes: 8cc196d6ef86 ("neighbor: gc_list changes should be protected by table lock") Signed-off-by: David Ahern <dsahern@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core/neighbour.c')
-rw-r--r--net/core/neighbour.c27
1 files changed, 15 insertions, 12 deletions
diff --git a/net/core/neighbour.c b/net/core/neighbour.c
index 03fdc5ae66b0..010784123bc1 100644
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -127,30 +127,30 @@ static void neigh_mark_dead(struct neighbour *n)
}
}
-static void neigh_change_state(struct neighbour *n, u8 new)
+static void neigh_update_gc_list(struct neighbour *n)
{
- bool on_gc_list = !list_empty(&n->gc_list);
- bool new_is_perm = new & NUD_PERMANENT;
+ bool on_gc_list, new_is_perm;
- n->nud_state = new;
+ write_lock_bh(&n->tbl->lock);
+ write_lock(&n->lock);
/* remove from the gc list if new state is permanent;
* add to the gc list if new state is not permanent
*/
+ new_is_perm = n->nud_state & NUD_PERMANENT;
+ on_gc_list = !list_empty(&n->gc_list);
+
if (new_is_perm && on_gc_list) {
- write_lock_bh(&n->tbl->lock);
list_del_init(&n->gc_list);
- write_unlock_bh(&n->tbl->lock);
-
atomic_dec(&n->tbl->gc_entries);
} else if (!new_is_perm && !on_gc_list) {
/* add entries to the tail; cleaning removes from the front */
- write_lock_bh(&n->tbl->lock);
list_add_tail(&n->gc_list, &n->tbl->gc_list);
- write_unlock_bh(&n->tbl->lock);
-
atomic_inc(&n->tbl->gc_entries);
}
+
+ write_unlock(&n->lock);
+ write_unlock_bh(&n->tbl->lock);
}
static bool neigh_del(struct neighbour *n, __u8 state, __u8 flags,
@@ -1220,7 +1220,7 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr,
neigh_del_timer(neigh);
if (old & NUD_CONNECTED)
neigh_suspect(neigh);
- neigh_change_state(neigh, new);
+ neigh->nud_state = new;
err = 0;
notify = old & NUD_VALID;
if ((old & (NUD_INCOMPLETE | NUD_PROBE)) &&
@@ -1299,7 +1299,7 @@ static int __neigh_update(struct neighbour *neigh, const u8 *lladdr,
((new & NUD_REACHABLE) ?
neigh->parms->reachable_time :
0)));
- neigh_change_state(neigh, new);
+ neigh->nud_state = new;
notify = 1;
}
@@ -1360,6 +1360,9 @@ out:
neigh_update_is_router(neigh, flags, &notify);
write_unlock_bh(&neigh->lock);
+ if ((new ^ old) & NUD_PERMANENT)
+ neigh_update_gc_list(neigh);
+
if (notify)
neigh_update_notify(neigh, nlmsg_pid);