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Subject: Re: Regression in unix stream sockets with the Smack LSM
To:     "Jiang Wang ." <jiang.wang@bytedance.com>
Cc:     Paul Moore <paul@paul-moore.com>,
        Andrii Nakryiko <andrii@kernel.org>,
        Jakub Sitnicki <jakub@cloudflare.com>,
        John Fastabend <john.fastabend@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linux Security Module list 
        <linux-security-module@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        Casey Schaufler <casey@schaufler-ca.com>
References: <a507efa7-066b-decf-8605-89cdb0ac1951.ref@schaufler-ca.com>
 <a507efa7-066b-decf-8605-89cdb0ac1951@schaufler-ca.com>
 <CAHC9VhR9SKX_-SAmtcCj+vuUvcdq-SWzKs86BKMjBcC8GhJ1gg@mail.gmail.com>
 <dd58bbf5-7983-ca26-c335-6bf8e492fcaa@schaufler-ca.com>
 <CAP_N_Z9iCP_xNNNSRVEzgGER7Zg+bb_nROzBUct=V6UyWn1P5A@mail.gmail.com>
From:   Casey Schaufler <casey@schaufler-ca.com>
Message-ID: <2409eb92-aff5-7e1f-db9d-3c3ff3a12ad7@schaufler-ca.com>
Date:   Mon, 20 Sep 2021 16:44:30 -0700
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On 9/20/2021 3:35 PM, Jiang Wang . wrote:
> On Wed, Sep 15, 2021 at 9:52 AM Casey Schaufler <casey@schaufler-ca.com=
> wrote:
>> On 9/13/2021 4:47 PM, Paul Moore wrote:
>>> On Mon, Sep 13, 2021 at 6:53 PM Casey Schaufler <casey@schaufler-ca.c=
om> wrote:
>>>> Commit 77462de14a43f4d98dbd8de0f5743a4e02450b1d
>>>>
>>>>         af_unix: Add read_sock for stream socket types
>>>>
>>>> introduced a regression in UDS socket connections for the Smack LSM.=

>>>> I have not tracked done the details of why the change broke the code=
,
>>>> but this is where bisecting the kernel indicates the problem lies, a=
nd
>>>> I have verified that reverting this change repairs the problem.
>>>>
>>>> You can verify the problem with the Smack test suite:
>>>>
>>>>         https://github.com/smack-team/smack-testsuite.git
>>>>
>>>> The failing test is tests/uds-access.sh.
>>>>
> I tried to reproduce with tests/uds-access.sh, but the first two test
> cases always failed.

That was my initial impression as well. However, when I started
running the tests outside the routine "make test-results" I started
observing that they succeeded irregularly.

My biggest concern is that the test ever fails. The uds-access test
has not failed in several releases. The erratic behavior just adds
spice to the problem.=20

>  I tried different kernels with and without my
> unix-stream sockmap patches. Also tried standard debian 4.19
> kernel and they all have the same result.  What distro did you use? cen=
tos?
> Fedora?

I have been testing on Fedora32 and Fedora34.

>  Have you tested on debian based distros?

Ubuntu 20.04.3 with a 5.15-rc1 kernel is exhibiting the same
behavior. The Ubuntu system fails the test more regularly, but
does succeed on occasion.

> failing log:
> root@gitlab-runner-stretch:~/smack-testsuite# tests/uds-access.sh -v

# tools/clean-targets.sh
# tests/uds-access.sh -v

will remove the UDS filesystem entry before the test runs.
=C2=A0

> mkdir: cannot create directory =E2=80=98./targets/uds-notroot=E2=80=99:=
 File exists
> tests/uds-access.sh:71 FAIL
> tests/uds-access.sh:76 FAIL
> tests/uds-access.sh:81 PASS
> tests/uds-access.sh:86 PASS
> tests/uds-access.sh:91 PASS
> tests/uds-access.sh PASS=3D3 FAIL=3D2
> root@gitlab-runner-stretch:~/smack-testsuite# uname -a
> Linux gitlab-runner-stretch 5.14.0-rc5.bm.1-amd64+ #6 SMP Mon Sep 20
> 22:01:10 UTC 2021 x86_64 GNU/Linux
> root@gitlab-runner-stretch:~/smack-testsuite#
>
>>>> I have not looked to see if there's a similar problem with SELinux.
>>>> There may be, but if there isn't it doesn't matter, there's still a
>>>> bug.
>>> FWIW, the selinux-testsuite tests ran clean today with v5.15-rc1 (it
>>> looks like this code is only in v5.15) but as Casey said, a regressio=
n
>>> is a regression.
>>>
>>> Casey, what actually fails on the Smack system with this commit?
>> This problem occurs with security=3Dnone as well as with security=3Dsm=
ack.
>>
>> There isn't a problem with connect, that always works correctly.
>> The problem is an unexpected read() failure in the connecting process.=

>> This doesn't occur all the time, and sometimes happens in the first
>> of my two tests, sometimes the second, sometimes neither and, you gues=
sed
>> it, sometimes both.
>>
>> Here's a sample socat log demonstrating the problem. The first run,
>> ending at "uds-access RC=3D0" behaves as expected. The second, ending
>> at "uds-access RC=3D1", demonstrates the read failure. This case was
> I tried to compare logs between RC=3D0 and RC=3D1, but they look  to me=

> not apple to apple comparison? The read syscall have different paramete=
rs
> and the syscall sequences are different. I am not sure which syscall
> is the first failure.  See more comments below.

The data being feed to socat is the Smack label, so the data passed acros=
s
the socket will be of different length ("Pop" vs. "Snap") between the
two test cases, but that should be the only difference.


>> run with Smack enabled, but I see the same problem with the same
>> unpredictability on the same kernel with security=3Dnone.
>>
>> I've tried to convince myself that there's a flaw in the way I've
>> set up the scripts. They've been pretty robust and I've never seen
>> socat behaving erratically before. I've instrumented the kernel
>> code and all the security checks are behaving as expected. Plus,
>> as I mentioned above, the problem also occurs without an LSM.
>>
>> 2021/09/15 08:49:50 socat[2215] D getpid()
>> 2021/09/15 08:49:50 socat[2215] D getpid() -> 2215
>> 2021/09/15 08:49:50 socat[2215] D setenv("SOCAT_PID", "2215", 1)
>> 2021/09/15 08:49:50 socat[2215] D setenv() -> 0
>> 2021/09/15 08:49:50 socat[2215] D setenv("SOCAT_PPID", "2215", 1)
>> 2021/09/15 08:49:50 socat[2215] D setenv() -> 0
>> 2021/09/15 08:49:50 socat[2215] I socat by Gerhard Rieger and contribu=
tors - see www.dest-unreach.org
>> 2021/09/15 08:49:50 socat[2215] I This product includes software devel=
oped by the OpenSSL Project for use in the OpenSSL Toolkit. (http://www.o=
penssl.org/)
>> 2021/09/15 08:49:50 socat[2215] I This product includes software writt=
en by Tim Hudson (tjh@cryptsoft.com)
>> 2021/09/15 08:49:50 socat[2215] D socat version 1.7.4.1 on Jan 27 2021=
 00:00:00
>> 2021/09/15 08:49:50 socat[2215] D setenv("SOCAT_VERSION", "1.7.4.1", 1=
)
>> 2021/09/15 08:49:50 socat[2215] D setenv() -> 0
>> 2021/09/15 08:49:50 socat[2215] D running on Linux version #58 SMP Wed=
 Sep 15 08:40:38 PDT 2021, release 5.15.0-rc1bisect, machine x86_64
>>
>> 2021/09/15 08:49:50 socat[2215] D argv[0]: "socat"
>> 2021/09/15 08:49:50 socat[2215] D argv[1]: "-d"
>> 2021/09/15 08:49:50 socat[2215] D argv[2]: "-d"
>> 2021/09/15 08:49:50 socat[2215] D argv[3]: "-d"
>> 2021/09/15 08:49:50 socat[2215] D argv[4]: "-d"
>> 2021/09/15 08:49:50 socat[2215] D argv[5]: "-"
>> 2021/09/15 08:49:50 socat[2215] D argv[6]: "UNIX-CONNECT:./targets/uds=
-notroot/uds-access-socket"
>> 2021/09/15 08:49:50 socat[2215] D sigaction(1, 0x7fffaec50b50, 0x0)
>> 2021/09/15 08:49:50 socat[2215] D sigaction() -> 0
>> 2021/09/15 08:49:50 socat[2215] D sigaction(2, 0x7fffaec50b50, 0x0)
>> 2021/09/15 08:49:50 socat[2215] D sigaction() -> 0
>> 2021/09/15 08:49:50 socat[2215] D sigaction(3, 0x7fffaec50b50, 0x0)
>> 2021/09/15 08:49:50 socat[2215] D sigaction() -> 0
>> 2021/09/15 08:49:50 socat[2215] D sigaction(4, 0x7fffaec50b50, 0x0)
>> 2021/09/15 08:49:50 socat[2215] D sigaction() -> 0
>> 2021/09/15 08:49:50 socat[2215] D sigaction(6, 0x7fffaec50b50, 0x0)
>> 2021/09/15 08:49:50 socat[2215] D sigaction() -> 0
>> 2021/09/15 08:49:50 socat[2215] D sigaction(7, 0x7fffaec50b50, 0x0)
>> 2021/09/15 08:49:50 socat[2215] D sigaction() -> 0
>> 2021/09/15 08:49:50 socat[2215] D sigaction(8, 0x7fffaec50b50, 0x0)
>> 2021/09/15 08:49:50 socat[2215] D sigaction() -> 0
>> 2021/09/15 08:49:50 socat[2215] D sigaction(11, 0x7fffaec50b50, 0x0)
>> 2021/09/15 08:49:50 socat[2215] D sigaction() -> 0
>> 2021/09/15 08:49:50 socat[2215] D sigaction(15, 0x7fffaec50b50, 0x0)
>> 2021/09/15 08:49:50 socat[2215] D sigaction() -> 0
>> 2021/09/15 08:49:50 socat[2215] D signal(13, 0x1)
>> 2021/09/15 08:49:50 socat[2215] D signal() -> 0x0
>> 2021/09/15 08:49:50 socat[2215] D atexit(0x55aa5d645110)
>> 2021/09/15 08:49:50 socat[2215] D atexit() -> 0
>> 2021/09/15 08:49:50 socat[2215] D xioopen("-")
>> 2021/09/15 08:49:50 socat[2215] D calloc(1, 824)
>> 2021/09/15 08:49:50 socat[2215] D calloc() -> 0x55aa5f0139d0
>> 2021/09/15 08:49:50 socat[2215] D malloc(1024)
>> 2021/09/15 08:49:50 socat[2215] D malloc() -> 0x55aa5f013d30
>> 2021/09/15 08:49:50 socat[2215] D calloc(1, 824)
>> 2021/09/15 08:49:50 socat[2215] D calloc() -> 0x55aa5f014140
>> 2021/09/15 08:49:50 socat[2215] D calloc(1, 824)
>> 2021/09/15 08:49:50 socat[2215] D calloc() -> 0x55aa5f014bc0
>> 2021/09/15 08:49:50 socat[2215] D isatty(0)
>> 2021/09/15 08:49:50 socat[2215] D isatty() -> 0
>> 2021/09/15 08:49:50 socat[2215] D isatty(1)
>> 2021/09/15 08:49:50 socat[2215] D isatty() -> 0
>> 2021/09/15 08:49:50 socat[2215] D malloc(128)
>> 2021/09/15 08:49:50 socat[2215] D malloc() -> 0x55aa5f014f00
>> 2021/09/15 08:49:50 socat[2215] D malloc(128)
>> 2021/09/15 08:49:50 socat[2215] D malloc() -> 0x55aa5f014f90
>> 2021/09/15 08:49:50 socat[2215] N reading from and writing to stdio
>> 2021/09/15 08:49:50 socat[2215] D xioopen("UNIX-CONNECT:./targets/uds-=
notroot/uds-access-socket")
>> 2021/09/15 08:49:50 socat[2215] D calloc(1, 824)
>> 2021/09/15 08:49:50 socat[2215] D calloc() -> 0x55aa5f015020
>> 2021/09/15 08:49:50 socat[2215] D malloc(1024)
>> 2021/09/15 08:49:50 socat[2215] D malloc() -> 0x55aa5f015360
>> 2021/09/15 08:49:50 socat[2215] D malloc(128)
>> 2021/09/15 08:49:50 socat[2215] D malloc() -> 0x55aa5f015770
>> 2021/09/15 08:49:50 socat[2215] N opening connection to AF=3D1 "./targ=
ets/uds-notroot/uds-access-socket"
>> 2021/09/15 08:49:50 socat[2215] D socket(1, 1, 0)
>> 2021/09/15 08:49:50 socat[2215] I socket(1, 1, 0) -> 5
>> 2021/09/15 08:49:50 socat[2215] D fcntl(5, 2, 1)
>> 2021/09/15 08:49:50 socat[2215] D fcntl() -> 0
>> 2021/09/15 08:49:50 socat[2215] D connect(5, {1,AF=3D1 "./targets/uds-=
notroot/uds-access-socket"}, 41)
>> 2021/09/15 08:49:50 socat[2215] D connect() -> 0
>> 2021/09/15 08:49:50 socat[2215] D getsockname(5, 0x7fffaec50580, 0x7ff=
faec50564{112})
>> 2021/09/15 08:49:50 socat[2215] D getsockname(, {AF=3D1 "<anon>"}, {2}=
) -> 0
>> 2021/09/15 08:49:50 socat[2215] N successfully connected from local ad=
dress AF=3D1 "uds-notroot/ud\xEE\xEE\xEE\xEEcess-socket")\n"
>> 2021/09/15 08:49:50 socat[2215] I resolved and opened all sock address=
es
>> 2021/09/15 08:49:50 socat[2215] D posix_memalign(0x7fffaec50b28, 4096,=
 16385)
>> 2021/09/15 08:49:50 socat[2215] D posix_memalign(...) -> 0
>> 2021/09/15 08:49:50 socat[2215] N starting data transfer loop with FDs=
 [0,1] and [5,5]
>> 2021/09/15 08:49:50 socat[2215] D data loop: sock1->eof=3D0, sock2->eo=
f=3D0, closing=3D0, wasaction=3D1, total_to=3D{0.000000}
>> 2021/09/15 08:49:50 socat[2215] D select(6, &0x21, &0x22, &0x0, NULL/0=
=2E000000)
>> 2021/09/15 08:49:50 socat[2215] D select -> (, 0x21, 0x22, 0x0, NULL/0=
=2E000000), 4
>> 2021/09/15 08:49:50 socat[2215] D read(0, 0x55aa5f016000, 8192)
>> 2021/09/15 08:49:50 socat[2215] D read -> 4
>> 2021/09/15 08:49:50 socat[2215] D write(5, 0x55aa5f016000, 4)
>> Pop
>> 2021/09/15 08:49:50 socat[2215] D write -> 4
>> 2021/09/15 08:49:50 socat[2215] I transferred 4 bytes from 0 to 5
>> 2021/09/15 08:49:50 socat[2215] D read(5, 0x55aa5f016000, 8192)
>> 2021/09/15 08:49:50 socat[2215] D read -> 4
>> 2021/09/15 08:49:50 socat[2215] D write(1, 0x55aa5f016000, 4)
>> Pop
>> 2021/09/15 08:49:50 socat[2215] D write -> 4
>> 2021/09/15 08:49:50 socat[2215] I transferred 4 bytes from 5 to 1
>> 2021/09/15 08:49:50 socat[2215] D data loop: sock1->eof=3D0, sock2->eo=
f=3D0, closing=3D0, wasaction=3D1, total_to=3D{0.000000}
>> 2021/09/15 08:49:50 socat[2215] D select(6, &0x21, &0x22, &0x0, NULL/0=
=2E000000)
>> 2021/09/15 08:49:50 socat[2215] D select -> (, 0x21, 0x22, 0x0, NULL/0=
=2E000000), 4
>> 2021/09/15 08:49:50 socat[2215] D read(0, 0x55aa5f016000, 8192)
>> 2021/09/15 08:49:50 socat[2215] D read -> 0
>> 2021/09/15 08:49:50 socat[2215] D read(5, 0x55aa5f016000, 8192)
>> 2021/09/15 08:49:50 socat[2215] D read -> 0
>> 2021/09/15 08:49:50 socat[2215] N socket 1 (fd 0) is at EOF
>> 2021/09/15 08:49:50 socat[2215] I shutdown(5, 1)
>> 2021/09/15 08:49:50 socat[2215] D shutdown()  -> 0
>> 2021/09/15 08:49:50 socat[2215] N socket 2 (fd 5) is at EOF
>> 2021/09/15 08:49:50 socat[2215] I shutdown(5, 2)
>> 2021/09/15 08:49:50 socat[2215] D shutdown()  -> 0
>> 2021/09/15 08:49:50 socat[2215] N exiting with status 0
>> 2021/09/15 08:49:50 socat[2215] D exit(0)
>> 2021/09/15 08:49:50 socat[2215] D starting xioexit()
>> 2021/09/15 08:49:50 socat[2215] D finished xioexit()
>> uds-access RC=3D0
>> 2021/09/15 08:49:52 socat[2240] D getpid()
>> 2021/09/15 08:49:52 socat[2240] D getpid() -> 2240
>> 2021/09/15 08:49:52 socat[2240] D setenv("SOCAT_PID", "2240", 1)
>> 2021/09/15 08:49:52 socat[2240] D setenv() -> 0
>> 2021/09/15 08:49:52 socat[2240] D setenv("SOCAT_PPID", "2240", 1)
>> 2021/09/15 08:49:52 socat[2240] D setenv() -> 0
>> 2021/09/15 08:49:52 socat[2240] I socat by Gerhard Rieger and contribu=
tors - see www.dest-unreach.org
>> 2021/09/15 08:49:52 socat[2240] I This product includes software devel=
oped by the OpenSSL Project for use in the OpenSSL Toolkit. (http://www.o=
penssl.org/)
>> 2021/09/15 08:49:52 socat[2240] I This product includes software writt=
en by Tim Hudson (tjh@cryptsoft.com)
>> 2021/09/15 08:49:52 socat[2240] D socat version 1.7.4.1 on Jan 27 2021=
 00:00:00
>> 2021/09/15 08:49:52 socat[2240] D setenv("SOCAT_VERSION", "1.7.4.1", 1=
)
>> 2021/09/15 08:49:52 socat[2240] D setenv() -> 0
>> 2021/09/15 08:49:52 socat[2240] D running on Linux version #58 SMP Wed=
 Sep 15 08:40:38 PDT 2021, release 5.15.0-rc1bisect, machine x86_64
>>
>> 2021/09/15 08:49:52 socat[2240] D argv[0]: "socat"
>> 2021/09/15 08:49:52 socat[2240] D argv[1]: "-d"
>> 2021/09/15 08:49:52 socat[2240] D argv[2]: "-d"
>> 2021/09/15 08:49:52 socat[2240] D argv[3]: "-d"
>> 2021/09/15 08:49:52 socat[2240] D argv[4]: "-d"
>> 2021/09/15 08:49:52 socat[2240] D argv[5]: "-"
>> 2021/09/15 08:49:52 socat[2240] D argv[6]: "UNIX-CONNECT:./targets/uds=
-notroot/uds-access-socket"
>> 2021/09/15 08:49:52 socat[2240] D sigaction(1, 0x7ffcca7e26c0, 0x0)
>> 2021/09/15 08:49:52 socat[2240] D sigaction() -> 0
>> 2021/09/15 08:49:52 socat[2240] D sigaction(2, 0x7ffcca7e26c0, 0x0)
>> 2021/09/15 08:49:52 socat[2240] D sigaction() -> 0
>> 2021/09/15 08:49:52 socat[2240] D sigaction(3, 0x7ffcca7e26c0, 0x0)
>> 2021/09/15 08:49:52 socat[2240] D sigaction() -> 0
>> 2021/09/15 08:49:52 socat[2240] D sigaction(4, 0x7ffcca7e26c0, 0x0)
>> 2021/09/15 08:49:52 socat[2240] D sigaction() -> 0
>> 2021/09/15 08:49:52 socat[2240] D sigaction(6, 0x7ffcca7e26c0, 0x0)
>> 2021/09/15 08:49:52 socat[2240] D sigaction() -> 0
>> 2021/09/15 08:49:52 socat[2240] D sigaction(7, 0x7ffcca7e26c0, 0x0)
>> 2021/09/15 08:49:52 socat[2240] D sigaction() -> 0
>> 2021/09/15 08:49:52 socat[2240] D sigaction(8, 0x7ffcca7e26c0, 0x0)
>> 2021/09/15 08:49:52 socat[2240] D sigaction() -> 0
>> 2021/09/15 08:49:52 socat[2240] D sigaction(11, 0x7ffcca7e26c0, 0x0)
>> 2021/09/15 08:49:52 socat[2240] D sigaction() -> 0
>> 2021/09/15 08:49:52 socat[2240] D sigaction(15, 0x7ffcca7e26c0, 0x0)
>> 2021/09/15 08:49:52 socat[2240] D sigaction() -> 0
>> 2021/09/15 08:49:52 socat[2240] D signal(13, 0x1)
>> 2021/09/15 08:49:52 socat[2240] D signal() -> 0x0
>> 2021/09/15 08:49:52 socat[2240] D atexit(0x560590a15110)
>> 2021/09/15 08:49:52 socat[2240] D atexit() -> 0
>> 2021/09/15 08:49:52 socat[2240] D xioopen("-")
>> 2021/09/15 08:49:52 socat[2240] D calloc(1, 824)
>> 2021/09/15 08:49:52 socat[2240] D calloc() -> 0x560591e899d0
>> 2021/09/15 08:49:52 socat[2240] D malloc(1024)
>> 2021/09/15 08:49:52 socat[2240] D malloc() -> 0x560591e89d30
>> 2021/09/15 08:49:52 socat[2240] D calloc(1, 824)
>> 2021/09/15 08:49:52 socat[2240] D calloc() -> 0x560591e8a140
>> 2021/09/15 08:49:52 socat[2240] D calloc(1, 824)
>> 2021/09/15 08:49:52 socat[2240] D calloc() -> 0x560591e8abc0
>> 2021/09/15 08:49:52 socat[2240] D isatty(0)
>> 2021/09/15 08:49:52 socat[2240] D isatty() -> 0
>> 2021/09/15 08:49:52 socat[2240] D isatty(1)
>> 2021/09/15 08:49:52 socat[2240] D isatty() -> 0
>> 2021/09/15 08:49:52 socat[2240] D malloc(128)
>> 2021/09/15 08:49:52 socat[2240] D malloc() -> 0x560591e8af00
>> 2021/09/15 08:49:52 socat[2240] D malloc(128)
>> 2021/09/15 08:49:52 socat[2240] D malloc() -> 0x560591e8af90
>> 2021/09/15 08:49:52 socat[2240] N reading from and writing to stdio
>> 2021/09/15 08:49:52 socat[2240] D xioopen("UNIX-CONNECT:./targets/uds-=
notroot/uds-access-socket")
>> 2021/09/15 08:49:52 socat[2240] D calloc(1, 824)
>> 2021/09/15 08:49:52 socat[2240] D calloc() -> 0x560591e8b020
>> 2021/09/15 08:49:52 socat[2240] D malloc(1024)
>> 2021/09/15 08:49:52 socat[2240] D malloc() -> 0x560591e8b360
>> 2021/09/15 08:49:52 socat[2240] D malloc(128)
>> 2021/09/15 08:49:52 socat[2240] D malloc() -> 0x560591e8b770
>> 2021/09/15 08:49:52 socat[2240] N opening connection to AF=3D1 "./targ=
ets/uds-notroot/uds-access-socket"
>> 2021/09/15 08:49:52 socat[2240] D socket(1, 1, 0)
>> 2021/09/15 08:49:52 socat[2240] I socket(1, 1, 0) -> 5
>> 2021/09/15 08:49:52 socat[2240] D fcntl(5, 2, 1)
>> 2021/09/15 08:49:52 socat[2240] D fcntl() -> 0
>> 2021/09/15 08:49:52 socat[2240] D connect(5, {1,AF=3D1 "./targets/uds-=
notroot/uds-access-socket"}, 41)
>> 2021/09/15 08:49:52 socat[2240] D connect() -> 0
>> 2021/09/15 08:49:52 socat[2240] D getsockname(5, 0x7ffcca7e20f0, 0x7ff=
cca7e20d4{112})
>> 2021/09/15 08:49:52 socat[2240] D getsockname(, {AF=3D1 "<anon>"}, {2}=
) -> 0
>> 2021/09/15 08:49:52 socat[2240] N successfully connected from local ad=
dress AF=3D1 "uds-notroot/ud\xEE\xEE\xEE\xEEcess-socket")\n"
>> 2021/09/15 08:49:52 socat[2240] I resolved and opened all sock address=
es
>> 2021/09/15 08:49:52 socat[2240] D posix_memalign(0x7ffcca7e2698, 4096,=
 16385)
>> 2021/09/15 08:49:52 socat[2240] D posix_memalign(...) -> 0
>> 2021/09/15 08:49:52 socat[2240] N starting data transfer loop with FDs=
 [0,1] and [5,5]
>> 2021/09/15 08:49:52 socat[2240] D data loop: sock1->eof=3D0, sock2->eo=
f=3D0, closing=3D0, wasaction=3D1, total_to=3D{0.000000}
>> 2021/09/15 08:49:52 socat[2240] D select(6, &0x21, &0x22, &0x0, NULL/0=
=2E000000)
>> 2021/09/15 08:49:52 socat[2240] D select -> (, 0x1, 0x22, 0x0, NULL/0.=
000000), 3
>> 2021/09/15 08:49:52 socat[2240] D read(0, 0x560591e8c000, 8192)
>> 2021/09/15 08:49:52 socat[2240] D read -> 5
>> 2021/09/15 08:49:52 socat[2240] D write(5, 0x560591e8c000, 5)
>> 2021/09/15 08:49:52 socat[2240] D write -> 5
>> 2021/09/15 08:49:52 socat[2240] I transferred 5 bytes from 0 to 5
>> 2021/09/15 08:49:52 socat[2240] D data loop: sock1->eof=3D0, sock2->eo=
f=3D0, closing=3D0, wasaction=3D1, total_to=3D{0.000000}
>> 2021/09/15 08:49:52 socat[2240] D select(6, &0x21, &0x20, &0x0, NULL/0=
=2E000000)
>> 2021/09/15 08:49:52 socat[2240] D select -> (, 0x1, 0x20, 0x0, NULL/0.=
000000), 2
>> 2021/09/15 08:49:52 socat[2240] D read(0, 0x560591e8c000, 8192)
>> 2021/09/15 08:49:52 socat[2240] D read -> 0
>> 2021/09/15 08:49:52 socat[2240] N socket 1 (fd 0) is at EOF
>> 2021/09/15 08:49:52 socat[2240] I shutdown(5, 1)
>> 2021/09/15 08:49:52 socat[2240] D shutdown()  -> 0
> Is this shutdown expected?

I'm not an expert on the internals of socat, but I don't think it
is expected.

> 2021/09/15 08:49:52 socat[2240] D data loop: sock1->eof=3D3, sock2->eof=
=3D0, closing=3D1, wasaction=3D1, total_to=3D{0.000000}
> 2021/09/15 08:49:52 socat[2240] D select(6, &0x20, &0x0, &0x0, &0.50000=
0)
> Snap
> 2021/09/15 08:49:52 socat[2240] D select -> (, 0x20, 0x0, 0x0, &0.50000=
0), 1
> 2021/09/15 08:49:52 socat[2240] D read(5, 0x560591e8c000, 8192)
> 2021/09/15 08:49:52 socat[2240] D read -> -1
> This read failure seems due to the previous shutdown, right?

Again, I'm not the socat expert, but that would seem reasonable
to me.


>> 2021/09/15 08:49:52 socat[2240] E read(5, 0x560591e8c000, 8192): Inval=
id argument
>> 2021/09/15 08:49:52 socat[2240] N exit(1)
>> 2021/09/15 08:49:52 socat[2240] D starting xioexit()
>> 2021/09/15 08:49:52 socat[2240] I shutdown(5, 2)
>> 2021/09/15 08:49:52 socat[2240] D shutdown()  -> 0
>> 2021/09/15 08:49:52 socat[2240] D finished xioexit()
>> uds-access RC=3D1
>>
>>
>>
>>