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mptcp: Correctly set DATA_FIN timeout when number of retransmits is large

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Syzkaller with UBSAN uncovered a scenario where a large number of
DATA_FIN retransmits caused a shift-out-of-bounds in the DATA_FIN
timeout calculation:

================================================================================
UBSAN: shift-out-of-bounds in net/mptcp/protocol.c:470:29
shift exponent 32 is too large for 32-bit type 'unsigned int'
CPU: 1 PID: 13059 Comm: kworker/1:0 Not tainted 5.17.0-rc2-00630-g5fbf21c90c60 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
Workqueue: events mptcp_worker
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 ubsan_epilogue+0xb/0x5a lib/ubsan.c:151
 __ubsan_handle_shift_out_of_bounds.cold+0xb2/0x20e lib/ubsan.c:330
 mptcp_set_datafin_timeout net/mptcp/protocol.c:470 [inline]
 __mptcp_retrans.cold+0x72/0x77 net/mptcp/protocol.c:2445
 mptcp_worker+0x58a/0xa70 net/mptcp/protocol.c:2528
 process_one_work+0x9df/0x16d0 kernel/workqueue.c:2307
 worker_thread+0x95/0xe10 kernel/workqueue.c:2454
 kthread+0x2f4/0x3b0 kernel/kthread.c:377
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
================================================================================

This change limits the maximum timeout by limiting the size of the
shift, which keeps all intermediate values in-bounds.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/259
Fixes: 6477dd39e6 ("mptcp: Retransmit DATA_FIN")
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Mat Martineau 2022-02-24 16:52:59 -08:00 committed by Jakub Kicinski
parent 63bb8239d8
commit 877d11f033
1 changed files with 5 additions and 2 deletions
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7
net/mptcp/protocol.c
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@ -466,9 +466,12 @@ static bool mptcp_pending_data_fin(struct sock *sk, u64 *seq)
static void mptcp_set_datafin_timeout(const struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);
u32 retransmits;
mptcp_sk(sk)->timer_ival = min(TCP_RTO_MAX,
TCP_RTO_MIN << icsk->icsk_retransmits);
retransmits = min_t(u32, icsk->icsk_retransmits,
ilog2(TCP_RTO_MAX / TCP_RTO_MIN));
mptcp_sk(sk)->timer_ival = TCP_RTO_MIN << retransmits;
}
static void __mptcp_set_timeout(struct sock *sk, long tout)