6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Florian Westphal fw@strlen.de
[ Upstream commit 087388278e0f301f4c61ddffb1911d3a180f84b8 ]
nft_rbtree_gc_elem() walks back and removes the end interval element that comes before the expired element.
There is a small chance that we've cached this element as 'rbe_ge'. If this happens, we hold and test a pointer that has been queued for freeing.
It also causes spurious insertion failures:
$ cat test-testcases-sets-0044interval_overlap_0.1/testout.log Error: Could not process rule: File exists add element t s { 0 - 2 } ^^^^^^ Failed to insert 0 - 2 given: table ip t { set s { type inet_service flags interval,timeout timeout 2s gc-interval 2s } }
The set (rbtree) is empty. The 'failure' doesn't happen on next attempt.
Reason is that when we try to insert, the tree may hold an expired element that collides with the range we're adding. While we do evict/erase this element, we can trip over this check:
if (rbe_ge && nft_rbtree_interval_end(rbe_ge) && nft_rbtree_interval_end(new)) return -ENOTEMPTY;
rbe_ge was erased by the synchronous gc, we should not have done this check. Next attempt won't find it, so retry results in successful insertion.
Restart in-kernel to avoid such spurious errors.
Such restart are rare, unless userspace intentionally adds very large numbers of elements with very short timeouts while setting a huge gc interval.
Even in this case, this cannot loop forever, on each retry an existing element has been removed.
As the caller is holding the transaction mutex, its impossible for a second entity to add more expiring elements to the tree.
After this it also becomes feasible to remove the async gc worker and perform all garbage collection from the commit path.
Fixes: c9e6978e2725 ("netfilter: nft_set_rbtree: Switch to node list walk for overlap detection") Signed-off-by: Florian Westphal fw@strlen.de Signed-off-by: Sasha Levin sashal@kernel.org --- net/netfilter/nft_set_rbtree.c | 46 +++++++++++++++++++++------------- 1 file changed, 29 insertions(+), 17 deletions(-)
diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c index 487572dcd6144..2660ceab3759d 100644 --- a/net/netfilter/nft_set_rbtree.c +++ b/net/netfilter/nft_set_rbtree.c @@ -233,10 +233,9 @@ static void nft_rbtree_gc_remove(struct net *net, struct nft_set *set, rb_erase(&rbe->node, &priv->root); }
-static int nft_rbtree_gc_elem(const struct nft_set *__set, - struct nft_rbtree *priv, - struct nft_rbtree_elem *rbe, - u8 genmask) +static const struct nft_rbtree_elem * +nft_rbtree_gc_elem(const struct nft_set *__set, struct nft_rbtree *priv, + struct nft_rbtree_elem *rbe, u8 genmask) { struct nft_set *set = (struct nft_set *)__set; struct rb_node *prev = rb_prev(&rbe->node); @@ -246,7 +245,7 @@ static int nft_rbtree_gc_elem(const struct nft_set *__set,
gc = nft_trans_gc_alloc(set, 0, GFP_ATOMIC); if (!gc) - return -ENOMEM; + return ERR_PTR(-ENOMEM);
/* search for end interval coming before this element. * end intervals don't carry a timeout extension, they @@ -261,6 +260,7 @@ static int nft_rbtree_gc_elem(const struct nft_set *__set, prev = rb_prev(prev); }
+ rbe_prev = NULL; if (prev) { rbe_prev = rb_entry(prev, struct nft_rbtree_elem, node); nft_rbtree_gc_remove(net, set, priv, rbe_prev); @@ -272,7 +272,7 @@ static int nft_rbtree_gc_elem(const struct nft_set *__set, */ gc = nft_trans_gc_queue_sync(gc, GFP_ATOMIC); if (WARN_ON_ONCE(!gc)) - return -ENOMEM; + return ERR_PTR(-ENOMEM);
nft_trans_gc_elem_add(gc, rbe_prev); } @@ -280,13 +280,13 @@ static int nft_rbtree_gc_elem(const struct nft_set *__set, nft_rbtree_gc_remove(net, set, priv, rbe); gc = nft_trans_gc_queue_sync(gc, GFP_ATOMIC); if (WARN_ON_ONCE(!gc)) - return -ENOMEM; + return ERR_PTR(-ENOMEM);
nft_trans_gc_elem_add(gc, rbe);
nft_trans_gc_queue_sync_done(gc);
- return 0; + return rbe_prev; }
static bool nft_rbtree_update_first(const struct nft_set *set, @@ -314,7 +314,7 @@ static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set, struct nft_rbtree *priv = nft_set_priv(set); u8 cur_genmask = nft_genmask_cur(net); u8 genmask = nft_genmask_next(net); - int d, err; + int d;
/* Descend the tree to search for an existing element greater than the * key value to insert that is greater than the new element. This is the @@ -363,9 +363,14 @@ static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set, */ if (nft_set_elem_expired(&rbe->ext) && nft_set_elem_active(&rbe->ext, cur_genmask)) { - err = nft_rbtree_gc_elem(set, priv, rbe, genmask); - if (err < 0) - return err; + const struct nft_rbtree_elem *removed_end; + + removed_end = nft_rbtree_gc_elem(set, priv, rbe, genmask); + if (IS_ERR(removed_end)) + return PTR_ERR(removed_end); + + if (removed_end == rbe_le || removed_end == rbe_ge) + return -EAGAIN;
continue; } @@ -486,11 +491,18 @@ static int nft_rbtree_insert(const struct net *net, const struct nft_set *set, struct nft_rbtree_elem *rbe = elem->priv; int err;
- write_lock_bh(&priv->lock); - write_seqcount_begin(&priv->count); - err = __nft_rbtree_insert(net, set, rbe, ext); - write_seqcount_end(&priv->count); - write_unlock_bh(&priv->lock); + do { + if (fatal_signal_pending(current)) + return -EINTR; + + cond_resched(); + + write_lock_bh(&priv->lock); + write_seqcount_begin(&priv->count); + err = __nft_rbtree_insert(net, set, rbe, ext); + write_seqcount_end(&priv->count); + write_unlock_bh(&priv->lock); + } while (err == -EAGAIN);
return err; }