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Miller" , Jakub Kicinski Cc: netdev , Eric Dumazet , Eric Dumazet , Willem de Bruijn , syzbot Subject: [PATCH net] udp: annotate data races around unix_sk(sk)->gso_size Date: Wed, 30 Jun 2021 09:42:44 -0700 Message-Id: <20210630164244.2180977-1-eric.dumazet@gmail.com> X-Mailer: git-send-email 2.32.0.93.g670b81a890-goog MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Eric Dumazet Accesses to unix_sk(sk)->gso_size are lockless. Add READ_ONCE()/WRITE_ONCE() around them. BUG: KCSAN: data-race in udp_lib_setsockopt / udpv6_sendmsg write to 0xffff88812d78f47c of 2 bytes by task 10849 on cpu 1: udp_lib_setsockopt+0x3b3/0x710 net/ipv4/udp.c:2696 udpv6_setsockopt+0x63/0x90 net/ipv6/udp.c:1630 sock_common_setsockopt+0x5d/0x70 net/core/sock.c:3265 __sys_setsockopt+0x18f/0x200 net/socket.c:2104 __do_sys_setsockopt net/socket.c:2115 [inline] __se_sys_setsockopt net/socket.c:2112 [inline] __x64_sys_setsockopt+0x62/0x70 net/socket.c:2112 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae read to 0xffff88812d78f47c of 2 bytes by task 10852 on cpu 0: udpv6_sendmsg+0x161/0x16b0 net/ipv6/udp.c:1299 inet6_sendmsg+0x5f/0x80 net/ipv6/af_inet6.c:642 sock_sendmsg_nosec net/socket.c:654 [inline] sock_sendmsg net/socket.c:674 [inline] ____sys_sendmsg+0x360/0x4d0 net/socket.c:2337 ___sys_sendmsg net/socket.c:2391 [inline] __sys_sendmmsg+0x315/0x4b0 net/socket.c:2477 __do_sys_sendmmsg net/socket.c:2506 [inline] __se_sys_sendmmsg net/socket.c:2503 [inline] __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2503 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47 entry_SYSCALL_64_after_hwframe+0x44/0xae value changed: 0x0000 -> 0x0005 Reported by Kernel Concurrency Sanitizer on: CPU: 0 PID: 10852 Comm: syz-executor.0 Not tainted 5.13.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Fixes: bec1f6f69736 ("udp: generate gso with UDP_SEGMENT") Signed-off-by: Eric Dumazet Cc: Willem de Bruijn Reported-by: syzbot --- net/ipv4/udp.c | 6 +++--- net/ipv6/udp.c | 2 +- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c index 62682807b4b2b8bdc2baf2205395ff78f253acf9..62cd4cd52e8481599f5e98c6022c96067e800f2d 100644 --- a/net/ipv4/udp.c +++ b/net/ipv4/udp.c @@ -1102,7 +1102,7 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) } ipcm_init_sk(&ipc, inet); - ipc.gso_size = up->gso_size; + ipc.gso_size = READ_ONCE(up->gso_size); if (msg->msg_controllen) { err = udp_cmsg_send(sk, msg, &ipc.gso_size); @@ -2695,7 +2695,7 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname, case UDP_SEGMENT: if (val < 0 || val > USHRT_MAX) return -EINVAL; - up->gso_size = val; + WRITE_ONCE(up->gso_size, val); break; case UDP_GRO: @@ -2790,7 +2790,7 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname, break; case UDP_SEGMENT: - val = up->gso_size; + val = READ_ONCE(up->gso_size); break; case UDP_GRO: diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c index 368972dbd91961e9915d4f6b1fd9542a8d8ed139..0cc7ba531b34157feca74b876b3aa5a4013fec04 100644 --- a/net/ipv6/udp.c +++ b/net/ipv6/udp.c @@ -1296,7 +1296,7 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len) int (*getfrag)(void *, char *, int, int, int, struct sk_buff *); ipcm6_init(&ipc6); - ipc6.gso_size = up->gso_size; + ipc6.gso_size = READ_ONCE(up->gso_size); ipc6.sockc.tsflags = sk->sk_tsflags; ipc6.sockc.mark = sk->sk_mark;