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authorEric Dumazet <edumazet@google.com>2021-10-04 14:24:15 -0700
committerDavid S. Miller <davem@davemloft.net>2021-10-05 13:11:09 +0100
commit7707a4d01a648e4c655101a469c956cb11273655 (patch)
tree9cac68d55159db0676abea2e56460838c2fbaa54 /net/netlink/af_netlink.c
parente3cf002d5a4452f8adc5543df341cf96fd702fcf (diff)
downloadlinux-7707a4d01a648e4c655101a469c956cb11273655.tar.bz2
netlink: annotate data races around nlk->bound
While existing code is correct, KCSAN is reporting a data-race in netlink_insert / netlink_sendmsg [1] It is correct to read nlk->bound without a lock, as netlink_autobind() will acquire all needed locks. [1] BUG: KCSAN: data-race in netlink_insert / netlink_sendmsg write to 0xffff8881031c8b30 of 1 bytes by task 18752 on cpu 0: netlink_insert+0x5cc/0x7f0 net/netlink/af_netlink.c:597 netlink_autobind+0xa9/0x150 net/netlink/af_netlink.c:842 netlink_sendmsg+0x479/0x7c0 net/netlink/af_netlink.c:1892 sock_sendmsg_nosec net/socket.c:703 [inline] sock_sendmsg net/socket.c:723 [inline] ____sys_sendmsg+0x360/0x4d0 net/socket.c:2392 ___sys_sendmsg net/socket.c:2446 [inline] __sys_sendmsg+0x1ed/0x270 net/socket.c:2475 __do_sys_sendmsg net/socket.c:2484 [inline] __se_sys_sendmsg net/socket.c:2482 [inline] __x64_sys_sendmsg+0x42/0x50 net/socket.c:2482 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae read to 0xffff8881031c8b30 of 1 bytes by task 18751 on cpu 1: netlink_sendmsg+0x270/0x7c0 net/netlink/af_netlink.c:1891 sock_sendmsg_nosec net/socket.c:703 [inline] sock_sendmsg net/socket.c:723 [inline] __sys_sendto+0x2a8/0x370 net/socket.c:2019 __do_sys_sendto net/socket.c:2031 [inline] __se_sys_sendto net/socket.c:2027 [inline] __x64_sys_sendto+0x74/0x90 net/socket.c:2027 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae value changed: 0x00 -> 0x01 Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 18751 Comm: syz-executor.0 Not tainted 5.14.0-rc1-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Fixes: da314c9923fe ("netlink: Replace rhash_portid with bound") Signed-off-by: Eric Dumazet <edumazet@google.com> Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/netlink/af_netlink.c')
-rw-r--r--net/netlink/af_netlink.c14
1 files changed, 10 insertions, 4 deletions
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 24b7cf447bc5..ada47e59647a 100644
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -594,7 +594,10 @@ static int netlink_insert(struct sock *sk, u32 portid)
/* We need to ensure that the socket is hashed and visible. */
smp_wmb();
- nlk_sk(sk)->bound = portid;
+ /* Paired with lockless reads from netlink_bind(),
+ * netlink_connect() and netlink_sendmsg().
+ */
+ WRITE_ONCE(nlk_sk(sk)->bound, portid);
err:
release_sock(sk);
@@ -1012,7 +1015,8 @@ static int netlink_bind(struct socket *sock, struct sockaddr *addr,
if (nlk->ngroups < BITS_PER_LONG)
groups &= (1UL << nlk->ngroups) - 1;
- bound = nlk->bound;
+ /* Paired with WRITE_ONCE() in netlink_insert() */
+ bound = READ_ONCE(nlk->bound);
if (bound) {
/* Ensure nlk->portid is up-to-date. */
smp_rmb();
@@ -1098,8 +1102,9 @@ static int netlink_connect(struct socket *sock, struct sockaddr *addr,
/* No need for barriers here as we return to user-space without
* using any of the bound attributes.
+ * Paired with WRITE_ONCE() in netlink_insert().
*/
- if (!nlk->bound)
+ if (!READ_ONCE(nlk->bound))
err = netlink_autobind(sock);
if (err == 0) {
@@ -1888,7 +1893,8 @@ static int netlink_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
dst_group = nlk->dst_group;
}
- if (!nlk->bound) {
+ /* Paired with WRITE_ONCE() in netlink_insert() */
+ if (!READ_ONCE(nlk->bound)) {
err = netlink_autobind(sock);
if (err)
goto out;