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Message-id: <20200708041030.24375-1-cpaasch@apple.com>
Date: Tue, 07 Jul 2020 21:10:30 -0700
From: Christoph Paasch <cpaasch@...le.com>
To: netdev@...r.kernel.org
Cc: David Miller <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>, Wei Wang <weiwan@...gle.com>,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net] tcp: Initialize ca_priv when inheriting from listener
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 by memsetting ca_priv to 0
after its content has been inherited by the listener.
(The issue can be reproduced at least down to v4.4.x.)
Cc: Wei Wang <weiwan@...gle.com>
Cc: Eric Dumazet <edumazet@...gle.com>
Fixes: 2b0a8c9ee ("tcp: add CDG congestion control")
Signed-off-by: Christoph Paasch <cpaasch@...le.com>
---
net/ipv4/inet_connection_sock.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index afaf582a5aa9..dc9432f9248a 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -850,6 +850,8 @@ struct sock *inet_csk_clone_lock(const struct sock *sk,
newicsk->icsk_backoff = 0;
newicsk->icsk_probes_out = 0;
+ memset(newicsk->icsk_ca_priv, 0, sizeof(newicsk->icsk_ca_priv));
+
/* Deinitialize accept_queue to trap illegal accesses. */
memset(&newicsk->icsk_accept_queue, 0, sizeof(newicsk->icsk_accept_queue));
--
2.23.0
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