From: Christoph Paasch cpaasch@apple.com
[ Upstream commit ce69e563b325f620863830c246a8698ccea52048 ]
syzkaller found its way into setsockopt with TCP_CONGESTION "cdg". tcp_cdg_init() does a kcalloc to store the gradients. As sk_clone_lock just copies all the memory, the allocated pointer will be copied as well, if the app called setsockopt(..., TCP_CONGESTION) on the listener. If now the socket will be destroyed before the congestion-control has properly been initialized (through a call to tcp_init_transfer), we will end up freeing memory that does not belong to that particular socket, opening the door to a double-free:
[ 11.413102] ================================================================== [ 11.414181] BUG: KASAN: double-free or invalid-free in tcp_cleanup_congestion_control+0x58/0xd0 [ 11.415329] [ 11.415560] CPU: 3 PID: 4884 Comm: syz-executor.5 Not tainted 5.8.0-rc2 #80 [ 11.416544] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 [ 11.418148] Call Trace: [ 11.418534] <IRQ> [ 11.418834] dump_stack+0x7d/0xb0 [ 11.419297] print_address_description.constprop.0+0x1a/0x210 [ 11.422079] kasan_report_invalid_free+0x51/0x80 [ 11.423433] __kasan_slab_free+0x15e/0x170 [ 11.424761] kfree+0x8c/0x230 [ 11.425157] tcp_cleanup_congestion_control+0x58/0xd0 [ 11.425872] tcp_v4_destroy_sock+0x57/0x5a0 [ 11.426493] inet_csk_destroy_sock+0x153/0x2c0 [ 11.427093] tcp_v4_syn_recv_sock+0xb29/0x1100 [ 11.427731] tcp_get_cookie_sock+0xc3/0x4a0 [ 11.429457] cookie_v4_check+0x13d0/0x2500 [ 11.433189] tcp_v4_do_rcv+0x60e/0x780 [ 11.433727] tcp_v4_rcv+0x2869/0x2e10 [ 11.437143] ip_protocol_deliver_rcu+0x23/0x190 [ 11.437810] ip_local_deliver+0x294/0x350 [ 11.439566] __netif_receive_skb_one_core+0x15d/0x1a0 [ 11.441995] process_backlog+0x1b1/0x6b0 [ 11.443148] net_rx_action+0x37e/0xc40 [ 11.445361] __do_softirq+0x18c/0x61a [ 11.445881] asm_call_on_stack+0x12/0x20 [ 11.446409] </IRQ> [ 11.446716] do_softirq_own_stack+0x34/0x40 [ 11.447259] do_softirq.part.0+0x26/0x30 [ 11.447827] __local_bh_enable_ip+0x46/0x50 [ 11.448406] ip_finish_output2+0x60f/0x1bc0 [ 11.450109] __ip_queue_xmit+0x71c/0x1b60 [ 11.451861] __tcp_transmit_skb+0x1727/0x3bb0 [ 11.453789] tcp_rcv_state_process+0x3070/0x4d3a [ 11.456810] tcp_v4_do_rcv+0x2ad/0x780 [ 11.457995] __release_sock+0x14b/0x2c0 [ 11.458529] release_sock+0x4a/0x170 [ 11.459005] __inet_stream_connect+0x467/0xc80 [ 11.461435] inet_stream_connect+0x4e/0xa0 [ 11.462043] __sys_connect+0x204/0x270 [ 11.465515] __x64_sys_connect+0x6a/0xb0 [ 11.466088] do_syscall_64+0x3e/0x70 [ 11.466617] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 11.467341] RIP: 0033:0x7f56046dc469 [ 11.467844] Code: Bad RIP value. [ 11.468282] RSP: 002b:00007f5604dccdd8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a [ 11.469326] RAX: ffffffffffffffda RBX: 000000000068bf00 RCX: 00007f56046dc469 [ 11.470379] RDX: 0000000000000010 RSI: 0000000020000000 RDI: 0000000000000004 [ 11.471311] RBP: 00000000ffffffff R08: 0000000000000000 R09: 0000000000000000 [ 11.472286] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 [ 11.473341] R13: 000000000041427c R14: 00007f5604dcd5c0 R15: 0000000000000003 [ 11.474321] [ 11.474527] Allocated by task 4884: [ 11.475031] save_stack+0x1b/0x40 [ 11.475548] __kasan_kmalloc.constprop.0+0xc2/0xd0 [ 11.476182] tcp_cdg_init+0xf0/0x150 [ 11.476744] tcp_init_congestion_control+0x9b/0x3a0 [ 11.477435] tcp_set_congestion_control+0x270/0x32f [ 11.478088] do_tcp_setsockopt.isra.0+0x521/0x1a00 [ 11.478744] __sys_setsockopt+0xff/0x1e0 [ 11.479259] __x64_sys_setsockopt+0xb5/0x150 [ 11.479895] do_syscall_64+0x3e/0x70 [ 11.480395] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [ 11.481097] [ 11.481321] Freed by task 4872: [ 11.481783] save_stack+0x1b/0x40 [ 11.482230] __kasan_slab_free+0x12c/0x170 [ 11.482839] kfree+0x8c/0x230 [ 11.483240] tcp_cleanup_congestion_control+0x58/0xd0 [ 11.483948] tcp_v4_destroy_sock+0x57/0x5a0 [ 11.484502] inet_csk_destroy_sock+0x153/0x2c0 [ 11.485144] tcp_close+0x932/0xfe0 [ 11.485642] inet_release+0xc1/0x1c0 [ 11.486131] __sock_release+0xc0/0x270 [ 11.486697] sock_close+0xc/0x10 [ 11.487145] __fput+0x277/0x780 [ 11.487632] task_work_run+0xeb/0x180 [ 11.488118] __prepare_exit_to_usermode+0x15a/0x160 [ 11.488834] do_syscall_64+0x4a/0x70 [ 11.489326] entry_SYSCALL_64_after_hwframe+0x44/0xa9
Wei Wang fixed a part of these CDG-malloc issues with commit c12014440750 ("tcp: memset ca_priv data to 0 properly").
This patch here fixes the listener-scenario: We make sure that listeners setting the congestion-control through setsockopt won't initialize it (thus CDG never allocates on listeners). For those who use AF_UNSPEC to reuse a socket, tcp_disconnect() is changed to cleanup afterwards.
(The issue can be reproduced at least down to v4.4.x.)
Cc: Wei Wang weiwan@google.com Cc: Eric Dumazet edumazet@google.com Fixes: 2b0a8c9eee81 ("tcp: add CDG congestion control") Signed-off-by: Christoph Paasch cpaasch@apple.com Signed-off-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/ipv4/tcp.c | 3 +++ net/ipv4/tcp_cong.c | 2 +- 2 files changed, 4 insertions(+), 1 deletion(-)
--- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2366,6 +2366,9 @@ int tcp_disconnect(struct sock *sk, int tp->snd_cwnd_cnt = 0; tp->window_clamp = 0; tp->delivered = 0; + if (icsk->icsk_ca_ops->release) + icsk->icsk_ca_ops->release(sk); + memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv)); tcp_set_ca_state(sk, TCP_CA_Open); tp->is_sack_reneg = 0; tcp_clear_retrans(tp); --- a/net/ipv4/tcp_cong.c +++ b/net/ipv4/tcp_cong.c @@ -199,7 +199,7 @@ static void tcp_reinit_congestion_contro icsk->icsk_ca_setsockopt = 1; memset(icsk->icsk_ca_priv, 0, sizeof(icsk->icsk_ca_priv));
- if (sk->sk_state != TCP_CLOSE) + if (!((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))) tcp_init_congestion_control(sk); }