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Wed, 27 Aug 2025 12:51:48 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com Authentication-Results: sina.com; spf=none smtp.mailfrom=hdanton@sina.com; dkim=none header.i=none; dmarc=none action=none header.from=hdanton@sina.com X-SMAIL-MID: 6810666816254 X-SMAIL-UIID: F1C4C5F7C2A942379DF3965E0F5A8C92-20250827-125148-1 From: Hillf Danton To: syzbot Cc: linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [net?] KASAN: slab-use-after-free Write in __xfrm_state_delete Date: Wed, 27 Aug 2025 12:51:37 +0800 Message-ID: <20250827045138.5764-1-hdanton@sina.com> In-Reply-To: <68ab6633.050a0220.37038e.0079.GAE@google.com> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit > Date: Sun, 24 Aug 2025 12:21:23 -0700 [thread overview] > syzbot has found a reproducer for the following issue on: > > HEAD commit: b1c92cdf5af3 Merge branch 'net-wangxun-complete-ethtool-co.. > git tree: net-next > console output: https://syzkaller.appspot.com/x/log.txt?x=1411b062580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=67b99ceb67d33475 > dashboard link: https://syzkaller.appspot.com/bug?extid=a25ee9d20d31e483ba7b > compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=14221862580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=159fba34580000 #syz test --- x/include/net/xfrm.h +++ y/include/net/xfrm.h @@ -202,6 +202,7 @@ struct xfrm_state { refcount_t refcnt; spinlock_t lock; + int deleted; u32 pcpu_num; struct xfrm_id id; --- x/net/xfrm/xfrm_state.c +++ y/net/xfrm/xfrm_state.c @@ -615,6 +615,7 @@ static void xfrm_state_gc_destroy(struct put_page(x->xfrag.page); xfrm_dev_state_free(x); security_xfrm_state_free(x); + xfrm_state_delete(x); xfrm_state_free(x); } @@ -812,10 +813,16 @@ int __xfrm_state_delete(struct xfrm_stat struct net *net = xs_net(x); int err = -ESRCH; - if (x->km.state != XFRM_STATE_DEAD) { - x->km.state = XFRM_STATE_DEAD; + for (;;) { + if (x->km.state != XFRM_STATE_DEAD) + x->km.state = XFRM_STATE_DEAD; spin_lock(&net->xfrm.xfrm_state_lock); + if (x->deleted) { + spin_unlock(&net->xfrm.xfrm_state_lock); + return 0; + } + x->deleted++; list_del(&x->km.all); hlist_del_rcu(&x->bydst); hlist_del_rcu(&x->bysrc); @@ -931,15 +938,16 @@ int xfrm_state_flush(struct net *net, u8 struct xfrm_state *x; restart: hlist_for_each_entry(x, net->xfrm.state_bydst+i, bydst) { - if (!xfrm_state_kern(x) && + if (!xfrm_state_kern(x) && x->km.state != XFRM_STATE_DEAD && xfrm_id_proto_match(x->id.proto, proto)) { xfrm_state_hold(x); spin_unlock_bh(&net->xfrm.xfrm_state_lock); - err = xfrm_state_delete(x); + err = 0; xfrm_audit_state_delete(x, err ? 0 : 1, task_valid); xfrm_state_put(x); + xfrm_state_put(x); if (!err) cnt++; --