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Miller" , Matthias Brugger , Sasha Levin , Simon Horman , Ryosuke Yasuoka , Zhengchao Shao , Pedro Tammela , Thomas Graf , , , , Subject: [PATCH 5.15 1/2] netlink: annotate lockless accesses to nlk->max_recvmsg_len Date: Wed, 15 May 2024 15:36:37 +0800 Message-ID: <20240515073644.32503-2-yenchia.chen@mediatek.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20240515073644.32503-1-yenchia.chen@mediatek.com> References: <20240515073644.32503-1-yenchia.chen@mediatek.com> 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 Content-Type: text/plain; charset="utf-8" From: Eric Dumazet syzbot reported a data-race in data-race in netlink_recvmsg() [1] Indeed, netlink_recvmsg() can be run concurrently, and netlink_dump() also needs protection. [1] BUG: KCSAN: data-race in netlink_recvmsg / netlink_recvmsg read to 0xffff888141840b38 of 8 bytes by task 23057 on cpu 0: netlink_recvmsg+0xea/0x730 net/netlink/af_netlink.c:1988 sock_recvmsg_nosec net/socket.c:1017 [inline] sock_recvmsg net/socket.c:1038 [inline] __sys_recvfrom+0x1ee/0x2e0 net/socket.c:2194 __do_sys_recvfrom net/socket.c:2212 [inline] __se_sys_recvfrom net/socket.c:2208 [inline] __x64_sys_recvfrom+0x78/0x90 net/socket.c:2208 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd write to 0xffff888141840b38 of 8 bytes by task 23037 on cpu 1: netlink_recvmsg+0x114/0x730 net/netlink/af_netlink.c:1989 sock_recvmsg_nosec net/socket.c:1017 [inline] sock_recvmsg net/socket.c:1038 [inline] ____sys_recvmsg+0x156/0x310 net/socket.c:2720 ___sys_recvmsg net/socket.c:2762 [inline] do_recvmmsg+0x2e5/0x710 net/socket.c:2856 __sys_recvmmsg net/socket.c:2935 [inline] __do_sys_recvmmsg net/socket.c:2958 [inline] __se_sys_recvmmsg net/socket.c:2951 [inline] __x64_sys_recvmmsg+0xe2/0x160 net/socket.c:2951 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd value changed: 0x0000000000000000 -> 0x0000000000001000 Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 23037 Comm: syz-executor.2 Not tainted 6.3.0-rc4-syzkaller-0019= 5-g5a57b48fdfcb #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Goo= gle 03/02/2023 Fixes: 9063e21fb026 ("netlink: autosize skb lengthes") Reported-by: syzbot Signed-off-by: Eric Dumazet Reviewed-by: Simon Horman Link: https://lore.kernel.org/r/20230403214643.768555-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: yenchia.chen Reviewed-by: Carlos Llamas --- net/netlink/af_netlink.c | 15 +++++++++------ 1 file changed, 9 insertions(+), 6 deletions(-) diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 82df02695bbd..56ba8a6396ca 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -1935,7 +1935,7 @@ static int netlink_recvmsg(struct socket *sock, struc= t msghdr *msg, size_t len, struct sock *sk =3D sock->sk; struct netlink_sock *nlk =3D nlk_sk(sk); int noblock =3D flags & MSG_DONTWAIT; - size_t copied; + size_t copied, max_recvmsg_len; struct sk_buff *skb, *data_skb; int err, ret; =20 @@ -1968,9 +1968,10 @@ static int netlink_recvmsg(struct socket *sock, stru= ct msghdr *msg, size_t len, #endif =20 /* Record the max length of recvmsg() calls for future allocations */ - nlk->max_recvmsg_len =3D max(nlk->max_recvmsg_len, len); - nlk->max_recvmsg_len =3D min_t(size_t, nlk->max_recvmsg_len, - SKB_WITH_OVERHEAD(32768)); + max_recvmsg_len =3D max(READ_ONCE(nlk->max_recvmsg_len), len); + max_recvmsg_len =3D min_t(size_t, max_recvmsg_len, + SKB_WITH_OVERHEAD(32768)); + WRITE_ONCE(nlk->max_recvmsg_len, max_recvmsg_len); =20 copied =3D data_skb->len; if (len < copied) { @@ -2219,6 +2220,7 @@ static int netlink_dump(struct sock *sk) struct netlink_ext_ack extack =3D {}; struct netlink_callback *cb; struct sk_buff *skb =3D NULL; + size_t max_recvmsg_len; struct module *module; int err =3D -ENOBUFS; int alloc_min_size; @@ -2241,8 +2243,9 @@ static int netlink_dump(struct sock *sk) cb =3D &nlk->cb; alloc_min_size =3D max_t(int, cb->min_dump_alloc, NLMSG_GOODSIZE); =20 - if (alloc_min_size < nlk->max_recvmsg_len) { - alloc_size =3D nlk->max_recvmsg_len; + max_recvmsg_len =3D READ_ONCE(nlk->max_recvmsg_len); + if (alloc_min_size < max_recvmsg_len) { + alloc_size =3D max_recvmsg_len; skb =3D alloc_skb(alloc_size, (GFP_KERNEL & ~__GFP_DIRECT_RECLAIM) | __GFP_NOWARN | __GFP_NORETRY); --=20 2.18.0