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Subject: Re: Regression in unix stream sockets with the Smack LSM
To:     Paul Moore <paul@paul-moore.com>
Cc:     Jiang Wang <jiang.wang@bytedance.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>
From:   Casey Schaufler <casey@schaufler-ca.com>
Message-ID: <dd58bbf5-7983-ca26-c335-6bf8e492fcaa@schaufler-ca.com>
Date:   Wed, 15 Sep 2021 09:51:58 -0700
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On 9/13/2021 4:47 PM, Paul Moore wrote:
> On Mon, Sep 13, 2021 at 6:53 PM Casey Schaufler <casey@schaufler-ca.com=
> 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, and=

>> 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 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 regression
> 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=3Dsmack=
=2E

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 guessed=

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
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 contributor=
s - see www.dest-unreach.org
2021/09/15 08:49:50 socat[2215] I This product includes software develope=
d by the OpenSSL Project for use in the OpenSSL Toolkit. (http://www.open=
ssl.org/)
2021/09/15 08:49:50 socat[2215] I This product includes software written =
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 Se=
p 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-no=
troot/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-not=
root/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 "./targets=
/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-not=
root/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, 0x7fffae=
c50564{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 addre=
ss 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 addresses
2021/09/15 08:49:50 socat[2215] D posix_memalign(0x7fffaec50b28, 4096, 16=
385)
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->eof=3D=
0, closing=3D0, wasaction=3D1, total_to=3D{0.000000}
2021/09/15 08:49:50 socat[2215] D select(6, &0x21, &0x22, &0x0, NULL/0.00=
0000)
2021/09/15 08:49:50 socat[2215] D select -> (, 0x21, 0x22, 0x0, NULL/0.00=
0000), 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->eof=3D=
0, closing=3D0, wasaction=3D1, total_to=3D{0.000000}
2021/09/15 08:49:50 socat[2215] D select(6, &0x21, &0x22, &0x0, NULL/0.00=
0000)
2021/09/15 08:49:50 socat[2215] D select -> (, 0x21, 0x22, 0x0, NULL/0.00=
0000), 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 contributor=
s - see www.dest-unreach.org
2021/09/15 08:49:52 socat[2240] I This product includes software develope=
d by the OpenSSL Project for use in the OpenSSL Toolkit. (http://www.open=
ssl.org/)
2021/09/15 08:49:52 socat[2240] I This product includes software written =
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 Se=
p 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-no=
troot/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-not=
root/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 "./targets=
/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-not=
root/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, 0x7ffcca=
7e20d4{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 addre=
ss 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 addresses
2021/09/15 08:49:52 socat[2240] D posix_memalign(0x7ffcca7e2698, 4096, 16=
385)
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->eof=3D=
0, closing=3D0, wasaction=3D1, total_to=3D{0.000000}
2021/09/15 08:49:52 socat[2240] D select(6, &0x21, &0x22, &0x0, NULL/0.00=
0000)
2021/09/15 08:49:52 socat[2240] D select -> (, 0x1, 0x22, 0x0, NULL/0.000=
000), 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->eof=3D=
0, closing=3D0, wasaction=3D1, total_to=3D{0.000000}
2021/09/15 08:49:52 socat[2240] D select(6, &0x21, &0x20, &0x0, NULL/0.00=
0000)
2021/09/15 08:49:52 socat[2240] D select -> (, 0x1, 0x20, 0x0, NULL/0.000=
000), 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
2021/09/15 08:49:52 socat[2240] D data loop: sock1->eof=3D3, sock2->eof=3D=
0, closing=3D1, wasaction=3D1, total_to=3D{0.000000}
2021/09/15 08:49:52 socat[2240] D select(6, &0x20, &0x0, &0x0, &0.500000)=

Snap
2021/09/15 08:49:52 socat[2240] D select -> (, 0x20, 0x0, 0x0, &0.500000)=
, 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
2021/09/15 08:49:52 socat[2240] E read(5, 0x560591e8c000, 8192): Invalid =
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

=C2=A0