* [PATCH nf] netfilter: nft_set_rbtree: skip transaction elements during GC
@ 2026-09-21 2:08 bestswngs
2026-09-21 12:08 ` Pablo Neira Ayuso
2026-09-21 20:48 ` Pablo Neira Ayuso
0 siblings, 2 replies; 4+ messages in thread
From: bestswngs @ 2026-09-21 2:08 UTC (permalink / raw)
To: pablo, fw, netfilter-devel, coreteam
Cc: phil, xmei5, Weiming Shi, co+ee5e50ef2670e5f4
From: Weiming Shi <bestswngs@gmail.com>
Since nft_set_commit_update() runs set commit callbacks before processing
NEWSETELEM transactions, nft_rbtree_gc_scan() can observe elements added by
the transaction being committed.
The scan records an interval end in rbe_end without checking the element's
transaction state. A later, unrelated expired start then moves both
elements to the expired list. The synchronous GC queue can free the new end
element before the transaction subsequently activates it, causing a
use-after-free.
Only consider elements that are fully active in both generations. This
keeps transaction-state elements out of the GC scan and preserves interval
pairing across skipped elements.
KASAN reports:
BUG: KASAN: slab-use-after-free in nft_setelem_activate
nft_setelem_activate net/netfilter/nf_tables_api.c:7047
nf_tables_commit net/netfilter/nf_tables_api.c:11137
Allocated by task 130:
nft_set_elem_init net/netfilter/nf_tables_api.c:6794
nft_add_set_elem net/netfilter/nf_tables_api.c:7523
Freed by task 130:
nft_trans_gc_trans_free net/netfilter/nf_tables_api.c:10506
rcu_core kernel/rcu/tree.c:2919
Fixes: 1e3b9e1c77fe ("netfilter: nf_tables: call set ops .commit when building new ruleset blob")
Reported-by: <co+ee5e50ef2670e5f4@bugs.sh>
Assisted-by: LLM
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
---
net/netfilter/nft_set_rbtree.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c
index 9894832281c4b..12431b55752fb 100644
--- a/net/netfilter/nft_set_rbtree.c
+++ b/net/netfilter/nft_set_rbtree.c
@@ -900,6 +900,8 @@ static void nft_rbtree_gc_scan(struct nft_set *set)
next = rb_next(node);
rbe = rb_entry(node, struct nft_rbtree_elem, node);
+ if (!nft_set_elem_active(&rbe->ext, NFT_GENMASK_ANY))
+ continue;
/* elements are reversed in the rbtree for historical reasons,
* from highest to lowest value, that is why end element is
--
2.55.0
^ permalink raw reply related [flat|nested] 4+ messages in thread* Re: [PATCH nf] netfilter: nft_set_rbtree: skip transaction elements during GC 2026-09-21 2:08 [PATCH nf] netfilter: nft_set_rbtree: skip transaction elements during GC bestswngs @ 2026-09-21 12:08 ` Pablo Neira Ayuso 2026-09-21 12:29 ` Pablo Neira Ayuso 2026-09-21 20:48 ` Pablo Neira Ayuso 1 sibling, 1 reply; 4+ messages in thread From: Pablo Neira Ayuso @ 2026-09-21 12:08 UTC (permalink / raw) To: bestswngs; +Cc: fw, netfilter-devel, coreteam, phil, xmei5, co+ee5e50ef2670e5f4 On Mon, Sep 21, 2026 at 10:08:22AM +0800, bestswngs@gmail.com wrote: > From: Weiming Shi <bestswngs@gmail.com> > > Since nft_set_commit_update() runs set commit callbacks before processing > NEWSETELEM transactions, nft_rbtree_gc_scan() can observe elements added by > the transaction being committed. > > The scan records an interval end in rbe_end without checking the element's > transaction state. A later, unrelated expired start then moves both > elements to the expired list. The synchronous GC queue can free the new end > element before the transaction subsequently activates it, causing a > use-after-free. > > Only consider elements that are fully active in both generations. This > keeps transaction-state elements out of the GC scan and preserves interval > pairing across skipped elements. > > KASAN reports: > > BUG: KASAN: slab-use-after-free in nft_setelem_activate > nft_setelem_activate net/netfilter/nf_tables_api.c:7047 > nf_tables_commit net/netfilter/nf_tables_api.c:11137 > > Allocated by task 130: > nft_set_elem_init net/netfilter/nf_tables_api.c:6794 > nft_add_set_elem net/netfilter/nf_tables_api.c:7523 > > Freed by task 130: > nft_trans_gc_trans_free net/netfilter/nf_tables_api.c:10506 > rcu_core kernel/rcu/tree.c:2919 > > Fixes: 1e3b9e1c77fe ("netfilter: nf_tables: call set ops .commit when building new ruleset blob") > Reported-by: <co+ee5e50ef2670e5f4@bugs.sh> > Assisted-by: LLM > Signed-off-by: Weiming Shi <bestswngs@gmail.com> > --- > net/netfilter/nft_set_rbtree.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c > index 9894832281c4b..12431b55752fb 100644 > --- a/net/netfilter/nft_set_rbtree.c > +++ b/net/netfilter/nft_set_rbtree.c > @@ -900,6 +900,8 @@ static void nft_rbtree_gc_scan(struct nft_set *set) > next = rb_next(node); > > rbe = rb_entry(node, struct nft_rbtree_elem, node); > + if (!nft_set_elem_active(&rbe->ext, NFT_GENMASK_ANY)) > + continue; > > /* elements are reversed in the rbtree for historical reasons, > * from highest to lowest value, that is why end element is Maybe simply set rbe_end to NULL when rbe is found and is not expired? diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c index 9894832281c4..a9f2ae3c91cf 100644 --- a/net/netfilter/nft_set_rbtree.c +++ b/net/netfilter/nft_set_rbtree.c @@ -909,8 +909,10 @@ static void nft_rbtree_gc_scan(struct nft_set *set) rbe_end = rbe; continue; } - if (!__nft_set_elem_expired(&rbe->ext, tstamp)) + if (!__nft_set_elem_expired(&rbe->ext, tstamp)) { + rbe_end = NULL; continue; + } /* end element needs to be removed first, it has * no timeout extension. ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH nf] netfilter: nft_set_rbtree: skip transaction elements during GC 2026-09-21 12:08 ` Pablo Neira Ayuso @ 2026-09-21 12:29 ` Pablo Neira Ayuso 0 siblings, 0 replies; 4+ messages in thread From: Pablo Neira Ayuso @ 2026-09-21 12:29 UTC (permalink / raw) To: bestswngs; +Cc: fw, netfilter-devel, coreteam, phil, xmei5, co+ee5e50ef2670e5f4 On Mon, Sep 21, 2026 at 02:08:40PM +0200, Pablo Neira Ayuso wrote: > On Mon, Sep 21, 2026 at 10:08:22AM +0800, bestswngs@gmail.com wrote: > > From: Weiming Shi <bestswngs@gmail.com> > > > > Since nft_set_commit_update() runs set commit callbacks before processing > > NEWSETELEM transactions, nft_rbtree_gc_scan() can observe elements added by > > the transaction being committed. > > > > The scan records an interval end in rbe_end without checking the element's > > transaction state. A later, unrelated expired start then moves both > > elements to the expired list. > > > > The synchronous GC queue can free the new end > > element before the transaction subsequently activates it, causing a > > use-after-free. > > > > Only consider elements that are fully active in both generations. This > > keeps transaction-state elements out of the GC scan and preserves interval > > pairing across skipped elements. > > > > KASAN reports: > > > > BUG: KASAN: slab-use-after-free in nft_setelem_activate > > nft_setelem_activate net/netfilter/nf_tables_api.c:7047 > > nf_tables_commit net/netfilter/nf_tables_api.c:11137 > > > > Allocated by task 130: > > nft_set_elem_init net/netfilter/nf_tables_api.c:6794 > > nft_add_set_elem net/netfilter/nf_tables_api.c:7523 > > > > Freed by task 130: > > nft_trans_gc_trans_free net/netfilter/nf_tables_api.c:10506 > > rcu_core kernel/rcu/tree.c:2919 > > > > Fixes: 1e3b9e1c77fe ("netfilter: nf_tables: call set ops .commit when building new ruleset blob") > > Reported-by: <co+ee5e50ef2670e5f4@bugs.sh> > > Assisted-by: LLM > > Signed-off-by: Weiming Shi <bestswngs@gmail.com> > > --- > > net/netfilter/nft_set_rbtree.c | 2 ++ > > 1 file changed, 2 insertions(+) > > > > diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c > > index 9894832281c4b..12431b55752fb 100644 > > --- a/net/netfilter/nft_set_rbtree.c > > +++ b/net/netfilter/nft_set_rbtree.c > > @@ -900,6 +900,8 @@ static void nft_rbtree_gc_scan(struct nft_set *set) > > next = rb_next(node); > > > > rbe = rb_entry(node, struct nft_rbtree_elem, node); > > + if (!nft_set_elem_active(&rbe->ext, NFT_GENMASK_ANY)) > > + continue; > > > > /* elements are reversed in the rbtree for historical reasons, > > * from highest to lowest value, that is why end element is > > Maybe simply set rbe_end to NULL when rbe is found and is not > expired? > > diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c > index 9894832281c4..a9f2ae3c91cf 100644 > --- a/net/netfilter/nft_set_rbtree.c > +++ b/net/netfilter/nft_set_rbtree.c > @@ -909,8 +909,10 @@ static void nft_rbtree_gc_scan(struct nft_set *set) > rbe_end = rbe; > continue; > } > - if (!__nft_set_elem_expired(&rbe->ext, tstamp)) > + if (!__nft_set_elem_expired(&rbe->ext, tstamp)) { > + rbe_end = NULL; > continue; > + } > > /* end element needs to be removed first, it has > * no timeout extension. My proposed chunk is not correct, it still allows for the problem to happen. Maybe restrict this to: diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c index 9894832281c4..bc331c6ae339 100644 --- a/net/netfilter/nft_set_rbtree.c +++ b/net/netfilter/nft_set_rbtree.c @@ -905,7 +905,8 @@ static void nft_rbtree_gc_scan(struct nft_set *set) * from highest to lowest value, that is why end element is * always visited before the start element. */ - if (nft_rbtree_interval_end(rbe)) { + if (nft_rbtree_interval_end(rbe) && + nft_set_elem_active(&rbe->ext, NFT_GENMASK_ANY)) { rbe_end = rbe; continue; } for symmetry with: commit 60c0c230c6f046da536d3df8b39a20b9a9fd6af0 Author: Pablo Neira Ayuso <pablo@netfilter.org> Date: Wed Feb 7 18:49:51 2024 +0100 netfilter: nft_set_rbtree: skip end interval element from gc But I suspect this is leaving stale (expired) overlapping intervals in the set when building it from nft_rbtree_commit(), so the fix still looks incomplete me. I want to have a close look and make a test case for this, this is not well covered by tests. ^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH nf] netfilter: nft_set_rbtree: skip transaction elements during GC 2026-09-21 2:08 [PATCH nf] netfilter: nft_set_rbtree: skip transaction elements during GC bestswngs 2026-09-21 12:08 ` Pablo Neira Ayuso @ 2026-09-21 20:48 ` Pablo Neira Ayuso 1 sibling, 0 replies; 4+ messages in thread From: Pablo Neira Ayuso @ 2026-09-21 20:48 UTC (permalink / raw) To: bestswngs; +Cc: fw, netfilter-devel, coreteam, phil, xmei5, co+ee5e50ef2670e5f4 On Mon, Sep 21, 2026 at 10:08:22AM +0800, bestswngs@gmail.com wrote: > From: Weiming Shi <bestswngs@gmail.com> > > Since nft_set_commit_update() runs set commit callbacks before processing > NEWSETELEM transactions, nft_rbtree_gc_scan() can observe elements added by > the transaction being committed. > > The scan records an interval end in rbe_end without checking the element's > transaction state. A later, unrelated expired start then moves both > elements to the expired list. The synchronous GC queue can free the new end > element before the transaction subsequently activates it, causing a > use-after-free. > > Only consider elements that are fully active in both generations. This > keeps transaction-state elements out of the GC scan and preserves interval > pairing across skipped elements. > > KASAN reports: > > BUG: KASAN: slab-use-after-free in nft_setelem_activate > nft_setelem_activate net/netfilter/nf_tables_api.c:7047 > nf_tables_commit net/netfilter/nf_tables_api.c:11137 > > Allocated by task 130: > nft_set_elem_init net/netfilter/nf_tables_api.c:6794 > nft_add_set_elem net/netfilter/nf_tables_api.c:7523 > > Freed by task 130: > nft_trans_gc_trans_free net/netfilter/nf_tables_api.c:10506 > rcu_core kernel/rcu/tree.c:2919 > > Fixes: 1e3b9e1c77fe ("netfilter: nf_tables: call set ops .commit when building new ruleset blob") > Reported-by: <co+ee5e50ef2670e5f4@bugs.sh> > Assisted-by: LLM > Signed-off-by: Weiming Shi <bestswngs@gmail.com> Patch is fine. It is not possible to add or delete an expired element, expired elements should not ever be in a transaction then. > --- > net/netfilter/nft_set_rbtree.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/net/netfilter/nft_set_rbtree.c b/net/netfilter/nft_set_rbtree.c > index 9894832281c4b..12431b55752fb 100644 > --- a/net/netfilter/nft_set_rbtree.c > +++ b/net/netfilter/nft_set_rbtree.c > @@ -900,6 +900,8 @@ static void nft_rbtree_gc_scan(struct nft_set *set) > next = rb_next(node); > > rbe = rb_entry(node, struct nft_rbtree_elem, node); > + if (!nft_set_elem_active(&rbe->ext, NFT_GENMASK_ANY)) > + continue; > > /* elements are reversed in the rbtree for historical reasons, > * from highest to lowest value, that is why end element is > -- > 2.55.0 > ^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2026-09-21 20:48 UTC | newest] Thread overview: 4+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2026-09-21 2:08 [PATCH nf] netfilter: nft_set_rbtree: skip transaction elements during GC bestswngs 2026-09-21 12:08 ` Pablo Neira Ayuso 2026-09-21 12:29 ` Pablo Neira Ayuso 2026-09-21 20:48 ` Pablo Neira Ayuso
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