From nobody Fri Apr 17 07:14:00 2026 Received: from m16.mail.163.com (m16.mail.163.com [220.197.31.2]) (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 B3FDD2C3256; Tue, 24 Feb 2026 05:50:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=220.197.31.2 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771912244; cv=none; b=FzPu8fgCHHzanVPw/PnlWt6coqSHXGo0/miDpgMGXoWuJdY+r8e5JNgZyxUAF605c3yx0kb7F+PD+0LdPtPpqkzX+Bo8i3bFcri/CV4B3uMd6TKm3MYLJa4pErt59MpLivXxDUOEdf9oFHOZGDXbZqfPSG5s4HOyXu/MaegiJRc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771912244; c=relaxed/simple; bh=1xoHKza8D9qbpBu77QMbUCKoksai5zG0Vqlhugga9bc=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=BHdrmEmTY2JhDuECRqWWOCtzYGvK7AxsUcVG2z4ugIECdvt7lPuQ9s5/VuF2Q3zm+YTDYU507npkZjHBeR/arr7w5+oBFiIBorjZMQAMyI38pOHOcofUikbFWw9VBadZIlnrPoSfyu8xDSzZag81OBlWt5F16FLuSg1vsz2k/qs= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com; spf=pass smtp.mailfrom=163.com; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b=oQyXepRe; arc=none smtp.client-ip=220.197.31.2 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=163.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=163.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=163.com header.i=@163.com header.b="oQyXepRe" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=163.com; s=s110527; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=8X HdgUxzGg4cYygXrKsfiEyU8WflBm67ZhCwzxUsvwQ=; b=oQyXepReo/JUpKF/Bq cpTnM8X+gP2HxlGwsBx/g+WA6daUgeNZFhrMEZEHKM8kKX9LfjbzQzSVe6ctv3b1 X6uTfM1jExjFSbwB1mruRTkjIUTPuuIs7QjNnfRM58gO7rxNbgLuHjK2+v0FMMyR hpFkHOT0uYzesWyIR7A59kpSs= Received: from pek-lpg-core6.wrs.com (unknown []) by gzga-smtp-mtada-g0-2 (Coremail) with SMTP id _____wBXv3P4O51pjHizOg--.39411S2; Tue, 24 Feb 2026 13:49:46 +0800 (CST) From: Rahul Sharma To: gregkh@linuxfoundation.org, stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Eric Dumazet , syzbot+179fc225724092b8b2b2@syzkaller.appspotmail.com, Martin KaFai Lau , David Ahern , Jakub Kicinski , Rahul Sharma Subject: [PATCH 6.6.y] dst: fix races in rt6_uncached_list_del() and rt_del_uncached_list() Date: Tue, 24 Feb 2026 13:49:43 +0800 Message-Id: <20260224054943.3324184-1-black.hawk@163.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-CM-TRANSID: _____wBXv3P4O51pjHizOg--.39411S2 X-Coremail-Antispam: 1Uf129KBjvAXoWfGF1kWFW3Jw4xZF43Zr1kXwb_yoW8JF1fGo WFvws5Xr4xKa45t3WfAr12ga1FgF97XF17Zrsrur4FvF42v3s8ArySga15ZryxXa4fGa93 XFy2qr18Ga4UJr93n29KB7ZKAUJUUUU8529EdanIXcx71UUUUU7v73VFW2AGmfu7bjvjm3 AaLaJ3UbIYCTnIWIevJa73UjIFyTuYvjTR3KsjDUUUU X-CM-SenderInfo: 5eoduy4okd4yi6rwjhhfrp/xtbC+hrOaGmdO-ooxAAA3f Content-Type: text/plain; charset="utf-8" From: Eric Dumazet [ Upstream commit 9a6f0c4d5796ab89b5a28a890ce542344d58bd69 ] syzbot was able to crash the kernel in rt6_uncached_list_flush_dev() in an interesting way [1] Crash happens in list_del_init()/INIT_LIST_HEAD() while writing list->prev, while the prior write on list->next went well. static inline void INIT_LIST_HEAD(struct list_head *list) { WRITE_ONCE(list->next, list); // This went well WRITE_ONCE(list->prev, list); // Crash, @list has been freed. } Issue here is that rt6_uncached_list_del() did not attempt to lock ul->lock, as list_empty(&rt->dst.rt_uncached) returned true because the WRITE_ONCE(list->next, list) happened on the other CPU. We might use list_del_init_careful() and list_empty_careful(), or make sure rt6_uncached_list_del() always grabs the spinlock whenever rt->dst.rt_uncached_list has been set. A similar fix is neeed for IPv4. [1] BUG: KASAN: slab-use-after-free in INIT_LIST_HEAD include/linux/list.h:46 = [inline] BUG: KASAN: slab-use-after-free in list_del_init include/linux/list.h:296 = [inline] BUG: KASAN: slab-use-after-free in rt6_uncached_list_flush_dev net/ipv6/ro= ute.c:191 [inline] BUG: KASAN: slab-use-after-free in rt6_disable_ip+0x633/0x730 net/ipv6/rou= te.c:5020 Write of size 8 at addr ffff8880294cfa78 by task kworker/u8:14/3450 CPU: 0 UID: 0 PID: 3450 Comm: kworker/u8:14 Tainted: G L s= yzkaller #0 PREEMPT_{RT,(full)} Tainted: [L]=3DSOFTLOCKUP Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Goo= gle 10/25/2025 Workqueue: netns cleanup_net Call Trace: dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:378 [inline] print_report+0xca/0x240 mm/kasan/report.c:482 kasan_report+0x118/0x150 mm/kasan/report.c:595 INIT_LIST_HEAD include/linux/list.h:46 [inline] list_del_init include/linux/list.h:296 [inline] rt6_uncached_list_flush_dev net/ipv6/route.c:191 [inline] rt6_disable_ip+0x633/0x730 net/ipv6/route.c:5020 addrconf_ifdown+0x143/0x18a0 net/ipv6/addrconf.c:3853 addrconf_notify+0x1bc/0x1050 net/ipv6/addrconf.c:-1 notifier_call_chain+0x19d/0x3a0 kernel/notifier.c:85 call_netdevice_notifiers_extack net/core/dev.c:2268 [inline] call_netdevice_notifiers net/core/dev.c:2282 [inline] netif_close_many+0x29c/0x410 net/core/dev.c:1785 unregister_netdevice_many_notify+0xb50/0x2330 net/core/dev.c:12353 ops_exit_rtnl_list net/core/net_namespace.c:187 [inline] ops_undo_list+0x3dc/0x990 net/core/net_namespace.c:248 cleanup_net+0x4de/0x7b0 net/core/net_namespace.c:696 process_one_work kernel/workqueue.c:3257 [inline] process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 Allocated by task 803: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 unpoison_slab_object mm/kasan/common.c:340 [inline] __kasan_slab_alloc+0x6c/0x80 mm/kasan/common.c:366 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4953 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_noprof+0x18d/0x6c0 mm/slub.c:5270 dst_alloc+0x105/0x170 net/core/dst.c:89 ip6_dst_alloc net/ipv6/route.c:342 [inline] icmp6_dst_alloc+0x75/0x460 net/ipv6/route.c:3333 mld_sendpack+0x683/0xe60 net/ipv6/mcast.c:1844 mld_send_cr net/ipv6/mcast.c:2154 [inline] mld_ifc_work+0x83e/0xd60 net/ipv6/mcast.c:2693 process_one_work kernel/workqueue.c:3257 [inline] process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 Freed by task 20: kasan_save_stack mm/kasan/common.c:57 [inline] kasan_save_track+0x3e/0x80 mm/kasan/common.c:78 kasan_save_free_info+0x46/0x50 mm/kasan/generic.c:584 poison_slab_object mm/kasan/common.c:253 [inline] __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:285 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:2540 [inline] slab_free mm/slub.c:6670 [inline] kmem_cache_free+0x18f/0x8d0 mm/slub.c:6781 dst_destroy+0x235/0x350 net/core/dst.c:121 rcu_do_batch kernel/rcu/tree.c:2605 [inline] rcu_core kernel/rcu/tree.c:2857 [inline] rcu_cpu_kthread+0xba5/0x1af0 kernel/rcu/tree.c:2945 smpboot_thread_fn+0x542/0xa60 kernel/smpboot.c:160 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 Last potentially related work creation: kasan_save_stack+0x3e/0x60 mm/kasan/common.c:57 kasan_record_aux_stack+0xbd/0xd0 mm/kasan/generic.c:556 __call_rcu_common kernel/rcu/tree.c:3119 [inline] call_rcu+0xee/0x890 kernel/rcu/tree.c:3239 refdst_drop include/net/dst.h:266 [inline] skb_dst_drop include/net/dst.h:278 [inline] skb_release_head_state+0x71/0x360 net/core/skbuff.c:1156 skb_release_all net/core/skbuff.c:1180 [inline] __kfree_skb net/core/skbuff.c:1196 [inline] sk_skb_reason_drop+0xe9/0x170 net/core/skbuff.c:1234 kfree_skb_reason include/linux/skbuff.h:1322 [inline] tcf_kfree_skb_list include/net/sch_generic.h:1127 [inline] __dev_xmit_skb net/core/dev.c:4260 [inline] __dev_queue_xmit+0x26aa/0x3210 net/core/dev.c:4785 NF_HOOK_COND include/linux/netfilter.h:307 [inline] ip6_output+0x340/0x550 net/ipv6/ip6_output.c:247 NF_HOOK+0x9e/0x380 include/linux/netfilter.h:318 mld_sendpack+0x8d4/0xe60 net/ipv6/mcast.c:1855 mld_send_cr net/ipv6/mcast.c:2154 [inline] mld_ifc_work+0x83e/0xd60 net/ipv6/mcast.c:2693 process_one_work kernel/workqueue.c:3257 [inline] process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246 The buggy address belongs to the object at ffff8880294cfa00 which belongs to the cache ip6_dst_cache of size 232 The buggy address is located 120 bytes inside of freed 232-byte region [ffff8880294cfa00, ffff8880294cfae8) The buggy address belongs to the physical page: page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x294cf memcg:ffff88803536b781 flags: 0x80000000000000(node=3D0|zone=3D1) page_type: f5(slab) raw: 0080000000000000 ffff88802ff1c8c0 ffffea0000bf2bc0 dead000000000006 raw: 0000000000000000 00000000800c000c 00000000f5000000 ffff88803536b781 page dumped because: kasan: bad access detected page_owner tracks the page as allocated page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52820(GF= P_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 9, tgid 9 (kworker/0:0= ), ts 91119585830, free_ts 91088628818 set_page_owner include/linux/page_owner.h:32 [inline] post_alloc_hook+0x234/0x290 mm/page_alloc.c:1857 prep_new_page mm/page_alloc.c:1865 [inline] get_page_from_freelist+0x28c0/0x2960 mm/page_alloc.c:3915 __alloc_frozen_pages_noprof+0x181/0x370 mm/page_alloc.c:5210 alloc_pages_mpol+0xd1/0x380 mm/mempolicy.c:2486 alloc_slab_page mm/slub.c:3075 [inline] allocate_slab+0x86/0x3b0 mm/slub.c:3248 new_slab mm/slub.c:3302 [inline] ___slab_alloc+0xb10/0x13e0 mm/slub.c:4656 __slab_alloc+0xc6/0x1f0 mm/slub.c:4779 __slab_alloc_node mm/slub.c:4855 [inline] slab_alloc_node mm/slub.c:5251 [inline] kmem_cache_alloc_noprof+0x101/0x6c0 mm/slub.c:5270 dst_alloc+0x105/0x170 net/core/dst.c:89 ip6_dst_alloc net/ipv6/route.c:342 [inline] icmp6_dst_alloc+0x75/0x460 net/ipv6/route.c:3333 mld_sendpack+0x683/0xe60 net/ipv6/mcast.c:1844 mld_send_cr net/ipv6/mcast.c:2154 [inline] mld_ifc_work+0x83e/0xd60 net/ipv6/mcast.c:2693 process_one_work kernel/workqueue.c:3257 [inline] process_scheduled_works+0xad1/0x1770 kernel/workqueue.c:3340 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3421 kthread+0x711/0x8a0 kernel/kthread.c:463 ret_from_fork+0x510/0xa50 arch/x86/kernel/process.c:158 page last free pid 5859 tgid 5859 stack trace: reset_page_owner include/linux/page_owner.h:25 [inline] free_pages_prepare mm/page_alloc.c:1406 [inline] __free_frozen_pages+0xfe1/0x1170 mm/page_alloc.c:2943 discard_slab mm/slub.c:3346 [inline] __put_partials+0x149/0x170 mm/slub.c:3886 __slab_free+0x2af/0x330 mm/slub.c:5952 qlink_free mm/kasan/quarantine.c:163 [inline] qlist_free_all+0x97/0x100 mm/kasan/quarantine.c:179 kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:350 kasan_slab_alloc include/linux/kasan.h:253 [inline] slab_post_alloc_hook mm/slub.c:4953 [inline] slab_alloc_node mm/slub.c:5263 [inline] kmem_cache_alloc_noprof+0x18d/0x6c0 mm/slub.c:5270 getname_flags+0xb8/0x540 fs/namei.c:146 getname include/linux/fs.h:2498 [inline] do_sys_openat2+0xbc/0x200 fs/open.c:1426 do_sys_open fs/open.c:1436 [inline] __do_sys_openat fs/open.c:1452 [inline] __se_sys_openat fs/open.c:1447 [inline] __x64_sys_openat+0x138/0x170 fs/open.c:1447 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xec/0xf80 arch/x86/entry/syscall_64.c:94 Fixes: 8d0b94afdca8 ("ipv6: Keep track of DST_NOCACHE routes in case of ifa= ce down/unregister") Fixes: 78df76a065ae ("ipv4: take rt_uncached_lock only if needed") Reported-by: syzbot+179fc225724092b8b2b2@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/6964cdf2.050a0220.eaf7.009d.GAE@goog= le.com/T/#u Signed-off-by: Eric Dumazet Cc: Martin KaFai Lau Reviewed-by: David Ahern Link: https://patch.msgid.link/20260112103825.3810713-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Rahul Sharma --- net/core/dst.c | 1 + net/ipv4/route.c | 4 ++-- net/ipv6/route.c | 4 ++-- 3 files changed, 5 insertions(+), 4 deletions(-) diff --git a/net/core/dst.c b/net/core/dst.c index 2513665696f6..5ed8cb10748f 100644 --- a/net/core/dst.c +++ b/net/core/dst.c @@ -68,6 +68,7 @@ void dst_init(struct dst_entry *dst, struct dst_ops *ops, dst->lwtstate =3D NULL; rcuref_init(&dst->__rcuref, initial_ref); INIT_LIST_HEAD(&dst->rt_uncached); + dst->rt_uncached_list =3D NULL; dst->__use =3D 0; dst->lastuse =3D jiffies; dst->flags =3D flags; diff --git a/net/ipv4/route.c b/net/ipv4/route.c index fcabacec89c7..55ea367f95b3 100644 --- a/net/ipv4/route.c +++ b/net/ipv4/route.c @@ -1546,9 +1546,9 @@ void rt_add_uncached_list(struct rtable *rt) =20 void rt_del_uncached_list(struct rtable *rt) { - if (!list_empty(&rt->dst.rt_uncached)) { - struct uncached_list *ul =3D rt->dst.rt_uncached_list; + struct uncached_list *ul =3D rt->dst.rt_uncached_list; =20 + if (ul) { spin_lock_bh(&ul->lock); list_del_init(&rt->dst.rt_uncached); spin_unlock_bh(&ul->lock); diff --git a/net/ipv6/route.c b/net/ipv6/route.c index ad452a04d729..5f7238f6a2dc 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -149,9 +149,9 @@ void rt6_uncached_list_add(struct rt6_info *rt) =20 void rt6_uncached_list_del(struct rt6_info *rt) { - if (!list_empty(&rt->dst.rt_uncached)) { - struct uncached_list *ul =3D rt->dst.rt_uncached_list; + struct uncached_list *ul =3D rt->dst.rt_uncached_list; =20 + if (ul) { spin_lock_bh(&ul->lock); list_del_init(&rt->dst.rt_uncached); spin_unlock_bh(&ul->lock); --=20 2.34.1