From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4EBD83EDAB8; Mon, 17 Aug 2026 13:40:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786974001; cv=none; b=frrXeiyXbvWTeJ/JmjyClOWBf/FqoRam2eNcFyZ3G3/riqGc0YJs4ls2MZfG8c/ls7aIhJRN007+BnZ+nmR+HXbrMgkeRKcaUWZhxqNAQiMCNwPIyd+Q364/F9NZN84HN3BKbBP6iCsma64IqHti82gGo08u3Y99/a0bOI5WjLo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786974001; c=relaxed/simple; bh=LSrVfRnG17gsUgl32GbwGUUgdAA5MnQiTW4mPy7T6BM=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=DJJsw6hkpijy2EDZ1QT/hb/OhsKkVn5hxVZcYpxHqyQSoa1PrgRzqxs6K0vsug2MhXB2Qpcuz8C1ILsLsdhFTvUFci2nraeZm6rN/c1pKbBtaGBiDrb24P1hYUpknSz3TzjLEFEZaZUh/sprYP7S+TvXoDC/qllyd2U3h4WpM8w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=xMpkd1xS; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="xMpkd1xS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 64C8C1F000E9; Mon, 17 Aug 2026 13:39:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1786973999; bh=BrXSrNnSP+NzRWyo8xr/4JksKhkNTdsEBBU12VpZf+M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=xMpkd1xSMu2hWQWytER2ZM9p55dyz4d2EI5mwhMWbz5TAwvvoj+O6yhknoWIvRBx7 XUpKaxNUTM1t3yoyYss7jU+05NNRB+PUxo+5UjgE+QMbq8nsBQsgA+5CymhRyyfYKo iyUYq28XiX242GM+vk5J/5P+QHVvOMl1p3ClhCEQ= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, zdi-disclosures@trendmicro.com, Santosh Kalluri , Paolo Abeni , Victor Nogueira , Jamal Hadi Salim , Jakub Kicinski , Sasha Levin Subject: [PATCH 7.1 055/271] net/sched: cls_route: fix fastmap use-after-free on filter Date: Mon, 17 Aug 2026 15:29:40 +0200 Message-ID: <20260817132539.007220466@linuxfoundation.org> X-Mailer: git-send-email 2.55.0 In-Reply-To: <20260817132536.752504388@linuxfoundation.org> References: <20260817132536.752504388@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 7.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jamal Hadi Salim [ Upstream commit 47d7f7051253bdc02b1d245d87e38f16d31a74df ] The route4 classifier maintains a 16-slot fastmap cache that stores raw struct route4_filter pointers indexed by (id, iif). The reader (route4_classify) populates this cache via route4_set_fastmap() for every classified packet that hits a filter. The writer (route4_delete, route4_change) clears the cache via route4_reset_fastmap() before RCU-deferred kfree of the filter. This creates a UAF race: 1. Reader walks the RCU-protected bucket chain, finds filter f 2. Writer unlinks f, calls route4_reset_fastmap(), then tcf_queue_work() 3. Reader calls route4_set_fastmap() and writes f into the cache *after* the writer's reset, caching a pointer about to be freed 4. After the RCU grace period, kfree(f) executes 5. Next classified packet on the same (id, iif) tuple hits the stale fastmap entry and reads f->res from freed memory Reproduced with an mdelay(100) accelerator in route4_set_fastmap() and a concurrent add/delete stress test (provided by both zdi and Santosh). Both triggered KASAN slab-use-after-free reports in the route4 fastmap paths. Fix: Introduce a per-filter boolean dying flag to suppress stale fastmap republishing by in-flight readers. Fixes: 1109c00547fc ("net: sched: RCU cls_route") Reported-by: zdi-disclosures@trendmicro.com Reported-by: Santosh Kalluri Suggested-by: Paolo Abeni Tested-by: Victor Nogueira Tested-by: Santosh Kalluri Signed-off-by: Jamal Hadi Salim Link: https://patch.msgid.link/20260729094411.46257-1-jhs@mojatatu.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin --- net/sched/cls_route.c | 35 ++++++++++++++++++++++++++--------- 1 file changed, 26 insertions(+), 9 deletions(-) diff --git a/net/sched/cls_route.c b/net/sched/cls_route.c index bd6f945bd3883..eded7aacd3f70 100644 --- a/net/sched/cls_route.c +++ b/net/sched/cls_route.c @@ -52,6 +52,7 @@ struct route4_filter { struct tcf_result res; struct tcf_exts exts; u32 handle; + bool dying; struct route4_bucket *bkt; struct tcf_proto *tp; struct rcu_work rwork; @@ -66,9 +67,11 @@ static inline int route4_fastmap_hash(u32 id, int iif) static DEFINE_SPINLOCK(fastmap_lock); static void -route4_reset_fastmap(struct route4_head *head) +route4_reset_fastmap(struct route4_head *head, struct route4_filter *f) { spin_lock_bh(&fastmap_lock); + if (f) + f->dying = true; memset(head->fastmap, 0, sizeof(head->fastmap)); spin_unlock_bh(&fastmap_lock); } @@ -81,9 +84,11 @@ route4_set_fastmap(struct route4_head *head, u32 id, int iif, /* fastmap updates must look atomic to aling id, iff, filter */ spin_lock_bh(&fastmap_lock); - head->fastmap[h].id = id; - head->fastmap[h].iif = iif; - head->fastmap[h].filter = f; + if (f == ROUTE4_FAILURE || !f->dying) { + head->fastmap[h].id = id; + head->fastmap[h].iif = iif; + head->fastmap[h].filter = f; + } spin_unlock_bh(&fastmap_lock); } @@ -297,6 +302,13 @@ static void route4_destroy(struct tcf_proto *tp, bool rtnl_held, next = rtnl_dereference(f->next); RCU_INIT_POINTER(b->ht[h2], next); tcf_unbind_filter(tp, &f->res); + /* Mark the filter dying under fastmap_lock so + * any in-flight reader that still holds it + * will skip the republish in route4_set_fastmap(). + */ + spin_lock_bh(&fastmap_lock); + f->dying = true; + spin_unlock_bh(&fastmap_lock); if (tcf_exts_get_net(&f->exts)) route4_queue_work(f); else @@ -307,6 +319,11 @@ static void route4_destroy(struct tcf_proto *tp, bool rtnl_held, kfree_rcu(b, rcu); } } + + /* All filters are unlinked and marked dying, so no in-flight + * reader can republish a stale entry after this reset. + */ + route4_reset_fastmap(head, NULL); kfree_rcu(head, rcu); } @@ -334,11 +351,11 @@ static int route4_delete(struct tcf_proto *tp, void *arg, bool *last, /* unlink it */ RCU_INIT_POINTER(*fp, rtnl_dereference(f->next)); - /* Remove any fastmap lookups that might ref filter - * notice we unlink'd the filter so we can't get it - * back in the fastmap. + /* Clear any fastmap entries that may ref this filter and + * mark it dying so in-flight readers can't republish it + * after the reset. */ - route4_reset_fastmap(head); + route4_reset_fastmap(head, f); /* Delete it */ tcf_unbind_filter(tp, &f->res); @@ -558,7 +575,7 @@ static int route4_change(struct net *net, struct sk_buff *in_skb, } } - route4_reset_fastmap(head); + route4_reset_fastmap(head, fold); *arg = f; if (fold) { tcf_unbind_filter(tp, &fold->res); -- 2.53.0