[PATCH] tcp: Do not reset the icsk_ca_initialized in tcp_init_transfer.

Neal Cardwell ncardwell at google.com
Mon Jun 28 17:20:19 UTC 2021


)

On Mon, Jun 28, 2021 at 1:15 PM Phi Nguyen <phind.uet at gmail.com> wrote:
>
> On 6/29/2021 12:24 AM, Neal Cardwell wrote:
>
> > Thanks.
> >
> > Can you also please provide a summary of the event sequence that
> > triggers the bug? Based on your Reported-by tag, I guess this is based
> > on the syzbot reproducer:
> >
> >   https://groups.google.com/g/syzkaller-bugs/c/VbHoSsBz0hk/m/cOxOoTgPCAAJ
> >
> > but perhaps you can give a summary of the event sequence that causes
> > the bug? Is it that the call:
> >
> > setsockopt$inet_tcp_TCP_CONGESTION(r0, 0x6, 0xd,
> > &(0x7f0000000000)='cdg\x00', 0x4)
> >
> > initializes the CC and happens before the connection is established,
> > and then when the connection is established, the line that sets:
> >    icsk->icsk_ca_initialized = 0;
> > is incorrect, causing the CC to be initialized again without first
> > calling the cleanup code that deallocates the CDG-allocated memory?
> >
> > thanks,
> > neal
> >
>
> Hi Neal,
>
> The gdb stack trace that lead to init_transfer_input() is as bellow, the
> current sock state is TCP_SYN_RECV.

Thanks. That makes sense as a snapshot of time for
tcp_init_transfer(), but I think what would be more useful would be a
description of the sequence of events, including when the CC was
initialized previous to that point (as noted above, was it that the
setsockopt(TCP_CONGESTION) completed before that point?).

thanks,
neal


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