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Miller" , Eric Dumazet , Jakub Kicinski , Simon Horman , Willem de Bruijn , David Ahern , Nathan Chancellor Subject: [PATCH net-next v2 3/5] udp_tunnel: fix UaF in GRO accounting Date: Fri, 21 Mar 2025 12:52:54 +0100 Message-ID: <70a8c5bdf58ed1937e2f3edbefb37c55cfe6ebc1.1742557254.git.pabeni@redhat.com> In-Reply-To: References: Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Patchwork-Delegate: kuba@kernel.org Siyzkaller reported a race in UDP tunnel GRO accounting, leading to UaF: BUG: KASAN: slab-use-after-free in udp_tunnel_update_gro_lookup+0x23c/0x2c0 net/ipv4/udp_offload.c:65 Read of size 8 at addr ffff88801235ebe8 by task syz.2.655/7921 CPU: 1 UID: 0 PID: 7921 Comm: syz.2.655 Not tainted 6.14.0-rc6-syzkaller-01313-g23c9ff659140 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025 Call Trace: __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:408 [inline] print_report+0x16e/0x5b0 mm/kasan/report.c:521 kasan_report+0x143/0x180 mm/kasan/report.c:634 udp_tunnel_update_gro_lookup+0x23c/0x2c0 net/ipv4/udp_offload.c:65 sk_common_release+0x71/0x2e0 net/core/sock.c:3896 inet_release+0x17d/0x200 net/ipv4/af_inet.c:435 __sock_release net/socket.c:647 [inline] sock_release+0x82/0x150 net/socket.c:675 sock_free drivers/net/wireguard/socket.c:339 [inline] wg_socket_reinit+0x215/0x380 drivers/net/wireguard/socket.c:435 wg_stop+0x59f/0x600 drivers/net/wireguard/device.c:133 __dev_close_many+0x3a6/0x700 net/core/dev.c:1717 dev_close_many+0x24e/0x4c0 net/core/dev.c:1742 unregister_netdevice_many_notify+0x629/0x24f0 net/core/dev.c:11923 rtnl_delete_link net/core/rtnetlink.c:3512 [inline] rtnl_dellink+0x526/0x8c0 net/core/rtnetlink.c:3554 rtnetlink_rcv_msg+0x791/0xcf0 net/core/rtnetlink.c:6945 netlink_rcv_skb+0x206/0x480 net/netlink/af_netlink.c:2534 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline] netlink_unicast+0x7f6/0x990 net/netlink/af_netlink.c:1339 netlink_sendmsg+0x8de/0xcb0 net/netlink/af_netlink.c:1883 sock_sendmsg_nosec net/socket.c:709 [inline] __sock_sendmsg+0x221/0x270 net/socket.c:724 ____sys_sendmsg+0x53a/0x860 net/socket.c:2564 ___sys_sendmsg net/socket.c:2618 [inline] __sys_sendmsg+0x269/0x350 net/socket.c:2650 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f35ab38d169 Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 RSP: 002b:00007f35ac28f038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f35ab5a6160 RCX: 00007f35ab38d169 RDX: 0000000000000000 RSI: 0000400000000000 RDI: 0000000000000004 RBP: 00007f35ab40e2a0 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000001 R14: 00007f35ab5a6160 R15: 00007ffdddd781b8 Allocated by task 7770: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 unpoison_slab_object mm/kasan/common.c:319 [inline] __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:345 kasan_slab_alloc include/linux/kasan.h:250 [inline] slab_post_alloc_hook mm/slub.c:4115 [inline] slab_alloc_node mm/slub.c:4164 [inline] kmem_cache_alloc_noprof+0x1d9/0x380 mm/slub.c:4171 sk_prot_alloc+0x58/0x210 net/core/sock.c:2190 sk_alloc+0x3e/0x370 net/core/sock.c:2249 inet_create+0x648/0xea0 net/ipv4/af_inet.c:326 __sock_create+0x4c0/0xa30 net/socket.c:1539 sock_create net/socket.c:1597 [inline] __sys_socket_create net/socket.c:1634 [inline] __sys_socket+0x150/0x3c0 net/socket.c:1681 __do_sys_socket net/socket.c:1695 [inline] __se_sys_socket net/socket.c:1693 [inline] __x64_sys_socket+0x7a/0x90 net/socket.c:1693 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f Freed by task 7768: kasan_save_stack mm/kasan/common.c:47 [inline] kasan_save_track+0x3f/0x80 mm/kasan/common.c:68 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:576 poison_slab_object mm/kasan/common.c:247 [inline] __kasan_slab_free+0x59/0x70 mm/kasan/common.c:264 kasan_slab_free include/linux/kasan.h:233 [inline] slab_free_hook mm/slub.c:2353 [inline] slab_free mm/slub.c:4609 [inline] kmem_cache_free+0x195/0x410 mm/slub.c:4711 sk_prot_free net/core/sock.c:2230 [inline] __sk_destruct+0x4fd/0x690 net/core/sock.c:2327 inet_release+0x17d/0x200 net/ipv4/af_inet.c:435 __sock_release net/socket.c:647 [inline] sock_close+0xbc/0x240 net/socket.c:1389 __fput+0x3e9/0x9f0 fs/file_table.c:464 task_work_run+0x24f/0x310 kernel/task_work.c:227 resume_user_mode_work include/linux/resume_user_mode.h:50 [inline] exit_to_user_mode_loop kernel/entry/common.c:114 [inline] exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline] __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline] syscall_exit_to_user_mode+0x13f/0x340 kernel/entry/common.c:218 do_syscall_64+0x100/0x230 arch/x86/entry/common.c:89 entry_SYSCALL_64_after_hwframe+0x77/0x7f The buggy address belongs to the object at ffff88801235e4c0 which belongs to the cache UDP of size 1856 The buggy address is located 1832 bytes inside of freed 1856-byte region [ffff88801235e4c0, ffff88801235ec00) At disposal time, to avoid unconditionally acquiring a spin lock, UDP tunnel sockets are conditionally removed from the known tunnels list only if the socket is actually present in such a list. Such check happens outside the socket lock scope: the current CPU could observe an uninitialized list entry even if the tunnel has been actually registered by a different core. Address the issue moving the blamed check under the relevant list spin lock. Reported-by: syzbot+1fb3291cc1beeb3c315a@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=1fb3291cc1beeb3c315a Fixes: 8d4880db37835 ("udp_tunnel: create a fastpath GRO lookup.") Signed-off-by: Paolo Abeni Reviewed-by: Willem de Bruijn --- include/net/udp_tunnel.h | 4 ---- net/ipv4/udp_offload.c | 3 ++- 2 files changed, 2 insertions(+), 5 deletions(-) diff --git a/include/net/udp_tunnel.h b/include/net/udp_tunnel.h index a7b230867eb14..13b54e6856414 100644 --- a/include/net/udp_tunnel.h +++ b/include/net/udp_tunnel.h @@ -214,14 +214,10 @@ static inline void udp_tunnel_update_gro_rcv(struct sock *sk, bool add) {} static inline void udp_tunnel_cleanup_gro(struct sock *sk) { - struct udp_sock *up = udp_sk(sk); struct net *net = sock_net(sk); udp_tunnel_update_gro_rcv(sk, false); - if (!up->tunnel_list.pprev) - return; - udp_tunnel_update_gro_lookup(net, sk, false); } diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c index fd2b8e3830beb..b124355a36aee 100644 --- a/net/ipv4/udp_offload.c +++ b/net/ipv4/udp_offload.c @@ -57,10 +57,11 @@ void udp_tunnel_update_gro_lookup(struct net *net, struct sock *sk, bool add) struct udp_tunnel_gro *udp_tunnel_gro; spin_lock(&udp_tunnel_gro_lock); + udp_tunnel_gro = &net->ipv4.udp_tunnel_gro[is_ipv6]; if (add) hlist_add_head(&up->tunnel_list, &udp_tunnel_gro->list); - else + else if (up->tunnel_list.pprev) hlist_del_init(&up->tunnel_list); if (udp_tunnel_gro->list.first &&