From: Eric Dumazet edumazet@google.com
[ Upstream commit a939d14919b799e6fff8a9c80296ca229ba2f8a4 ]
Both netlink_recvmsg() and netlink_native_seq_show() read nlk->cb_running locklessly. Use READ_ONCE() there.
Add corresponding WRITE_ONCE() to netlink_dump() and __netlink_dump_start()
syzbot reported: BUG: KCSAN: data-race in __netlink_dump_start / netlink_recvmsg
write to 0xffff88813ea4db59 of 1 bytes by task 28219 on cpu 0: __netlink_dump_start+0x3af/0x4d0 net/netlink/af_netlink.c:2399 netlink_dump_start include/linux/netlink.h:308 [inline] rtnetlink_rcv_msg+0x70f/0x8c0 net/core/rtnetlink.c:6130 netlink_rcv_skb+0x126/0x220 net/netlink/af_netlink.c:2577 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:6192 netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline] netlink_unicast+0x56f/0x640 net/netlink/af_netlink.c:1365 netlink_sendmsg+0x665/0x770 net/netlink/af_netlink.c:1942 sock_sendmsg_nosec net/socket.c:724 [inline] sock_sendmsg net/socket.c:747 [inline] sock_write_iter+0x1aa/0x230 net/socket.c:1138 call_write_iter include/linux/fs.h:1851 [inline] new_sync_write fs/read_write.c:491 [inline] vfs_write+0x463/0x760 fs/read_write.c:584 ksys_write+0xeb/0x1a0 fs/read_write.c:637 __do_sys_write fs/read_write.c:649 [inline] __se_sys_write fs/read_write.c:646 [inline] __x64_sys_write+0x42/0x50 fs/read_write.c:646 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
read to 0xffff88813ea4db59 of 1 bytes by task 28222 on cpu 1: netlink_recvmsg+0x3b4/0x730 net/netlink/af_netlink.c:2022 sock_recvmsg_nosec+0x4c/0x80 net/socket.c:1017 ____sys_recvmsg+0x2db/0x310 net/socket.c:2718 ___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: 0x00 -> 0x01
Fixes: 16b304f3404f ("netlink: Eliminate kmalloc in netlink dump operation.") Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/netlink/af_netlink.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c index 84a7a29be49d8..998c736d3ae8b 100644 --- a/net/netlink/af_netlink.c +++ b/net/netlink/af_netlink.c @@ -2000,7 +2000,7 @@ static int netlink_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
skb_free_datagram(sk, skb);
- if (nlk->cb_running && + if (READ_ONCE(nlk->cb_running) && atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf / 2) { ret = netlink_dump(sk); if (ret) { @@ -2312,7 +2312,7 @@ static int netlink_dump(struct sock *sk) if (cb->done) cb->done(cb);
- nlk->cb_running = false; + WRITE_ONCE(nlk->cb_running, false); module = cb->module; skb = cb->skb; mutex_unlock(nlk->cb_mutex); @@ -2375,7 +2375,7 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb, goto error_put; }
- nlk->cb_running = true; + WRITE_ONCE(nlk->cb_running, true); nlk->dump_done_errno = INT_MAX;
mutex_unlock(nlk->cb_mutex); @@ -2661,7 +2661,7 @@ static int netlink_native_seq_show(struct seq_file *seq, void *v) nlk->groups ? (u32)nlk->groups[0] : 0, sk_rmem_alloc_get(s), sk_wmem_alloc_get(s), - nlk->cb_running, + READ_ONCE(nlk->cb_running), refcount_read(&s->sk_refcnt), atomic_read(&s->sk_drops), sock_i_ino(s)