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[45.78.65.84]) by smtp.gmail.com with ESMTPSA id 956f58d0204a3-66cfb3671f5sm3062475d50.15.2026.08.24.08.23.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 24 Aug 2026 08:23:38 -0700 (PDT) From: Chengfeng Ye To: "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Chengfeng Ye , Willem de Bruijn , Nikolay Aleksandrov , Qi Zhang , Randy Dunlap , Alice Mikityanska , Florian Westphal , Jesper Dangaard Brouer Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: [PATCH net] net: pktgen: keep device lookup under RCU protection Date: Mon, 24 Aug 2026 23:23:31 +0800 Message-ID: <20260824152331.216494-1-nicoyip.dev@gmail.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit pktgen_find_dev() releases its RCU read-side critical section before returning pkt_dev. __pktgen_NN_threads() then sets removal_mark through that unprotected pointer. The worker can concurrently remove the device and queue it for RCU freeing: CPU 0 (netdevice unregister) CPU 1 (kpktgend) rcu_read_lock() find pkt_dev rcu_read_unlock() list_del_rcu(&pkt_dev->list) kfree_rcu(pkt_dev, rcu) RCU grace period ends pkt_dev->removal_mark = 1 The mutex held by CPU 0 does not cover the worker and does not delay an RCU grace period, so the final write can access freed memory. KASAN reported: BUG: KASAN: slab-use-after-free in __pktgen_NN_threads+0x241/0x280 Write of size 4 at addr ffff88810dab804c Call Trace: __pktgen_NN_threads+0x241/0x280 pktgen_device_event+0x24e/0x3d0 unregister_netdevice_many_notify+0xde8/0x1ec0 rtnl_dellink+0x35d/0xa90 Allocated by task 92: __kasan_kmalloc+0x8f/0xa0 pktgen_thread_write+0x498/0x14e0 Freed by task 0: __kasan_slab_free+0x43/0x70 rcu_core+0x50a/0x1850 Move the existing RCU read lock into the sole caller and release it only after setting removal_mark. The object therefore remains alive through the dereference, while lookup order and control handling remain unchanged. Fixes: 8788370a1d4b ("pktgen: RCU-ify "if_list" to remove lock in next_to_run()") Cc: stable@vger.kernel.org Signed-off-by: Chengfeng Ye --- net/core/pktgen.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/net/core/pktgen.c b/net/core/pktgen.c index 7f81aed46672..4fb1853589b3 100644 --- a/net/core/pktgen.c +++ b/net/core/pktgen.c @@ -2032,14 +2032,17 @@ static struct pktgen_dev *__pktgen_NN_threads(const struct pktgen_net *pn, bool exact = (remove == FIND); list_for_each_entry(t, &pn->pktgen_threads, th_list) { + rcu_read_lock(); pkt_dev = pktgen_find_dev(t, ifname, exact); if (pkt_dev) { if (remove) { pkt_dev->removal_mark = 1; t->control |= T_REMDEV; } - break; } + rcu_read_unlock(); + if (pkt_dev) + break; } return pkt_dev; } @@ -3776,7 +3779,6 @@ static struct pktgen_dev *pktgen_find_dev(struct pktgen_thread *t, struct pktgen_dev *p, *pkt_dev = NULL; size_t len = strlen(ifname); - rcu_read_lock(); list_for_each_entry_rcu(p, &t->if_list, list) if (strncmp(p->odevname, ifname, len) == 0) { if (p->odevname[len]) { @@ -3787,7 +3789,6 @@ static struct pktgen_dev *pktgen_find_dev(struct pktgen_thread *t, break; } - rcu_read_unlock(); pr_debug("find_dev(%s) returning %p\n", ifname, pkt_dev); return pkt_dev; } -- 2.43.0