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Message-ID: <6de04554b27e9573e0a65170916d6acf11285dba.camel@nokia.com>
Date: Wed, 2 Dec 2020 06:18:44 +0000
From: "Rantala, Tommi T. (Nokia - FI/Espoo)" <tommi.t.rantala@...ia.com>
To: "adobriyan@...il.com" <adobriyan@...il.com>
CC: "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: /proc/net/sctp/snmp, setns, proc: revalidate misc dentries
Hello,
Bisected problems with setns() and /proc/net/sctp/snmp to this:
commit 1da4d377f943fe4194ffb9fb9c26cc58fad4dd24
Author: Alexey Dobriyan <adobriyan@...il.com>
Date: Fri Apr 13 15:35:42 2018 -0700
proc: revalidate misc dentries
Reproduces for example with Fedora 5.9.10-100.fc32.x86_64, so 1fde6f21d90f
("proc: fix /proc/net/* after setns(2)") does not seem to cover
/proc/net/sctp/snmp
Reproducer attached, that does open+read+close of /proc/net/sctp/snmp before
and after setns() syscall. The second open+read+close of /proc/net/sctp/snmp
incorrectly produces results for the default namespace, not the target
namespace.
Example, create netns and do some sctp:
# ./iperf-netns
+ modprobe sctp
+ ip netns add test
+ ip netns exec test ip link set lo up
+ ip netns exec test iperf3 -s -1
-----------------------------------------------------------
Server listening on 5201
-----------------------------------------------------------
+ ip netns exec test iperf3 -c 127.0.0.1 --sctp --bitrate 50M --time 4
Connecting to host 127.0.0.1, port 5201
Accepted connection from 127.0.0.1, port 50696
[ 5] local 127.0.0.1 port 54735 connected to 127.0.0.1 port 5201
[ 5] local 127.0.0.1 port 5201 connected to 127.0.0.1 port 54735
[ ID] Interval Transfer Bitrate
[ ID] Interval Transfer Bitrate
[ 5] 0.00-1.00 sec 6.00 MBytes 50.3 Mbits/sec
[ 5] 0.00-1.00 sec 6.00 MBytes 50.3 Mbits/sec
[ 5] 1.00-2.00 sec 5.94 MBytes 49.8 Mbits/sec
[ 5] 1.00-2.00 sec 5.94 MBytes 49.8 Mbits/sec
[ 5] 2.00-3.00 sec 6.00 MBytes 50.3 Mbits/sec
[ 5] 2.00-3.00 sec 6.00 MBytes 50.3 Mbits/sec
[ 5] 3.00-4.00 sec 5.94 MBytes 49.8 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-4.00 sec 23.9 MBytes 50.1
Mbits/sec receiver
[ 5] 3.00-4.00 sec 5.94 MBytes 49.8 Mbits/sec
- - - - - - - - - - - - - - - - - - - - - - - - -
[ ID] Interval Transfer Bitrate
[ 5] 0.00-4.00 sec 23.9 MBytes 50.1 Mbits/sec
[ 5] 0.00-4.00 sec 23.9 MBytes 50.1
iperf Done.
+ cat /proc/net/sctp/snmp
SctpCurrEstab 0
SctpActiveEstabs 0
SctpPassiveEstabs 0
SctpAborteds 0
SctpShutdowns 0
SctpOutOfBlues 0
SctpChecksumErrors 0
[...]
+ ip netns exec test cat /proc/net/sctp/snmp
SctpCurrEstab 0
SctpActiveEstabs 2
SctpPassiveEstabs 2
SctpAborteds 0
SctpShutdowns 4
SctpOutOfBlues 0
SctpChecksumErrors 0
SctpOutCtrlChunks 1544
SctpOutOrderChunks 1530
[...]
+ wait
But now we see all zeroes in /proc/net/sctp/snmp with the reproducer:
$ gcc repro.c -o repro
# ./repro
/proc/net/sctp/snmp [pid: 175998]
SctpCurrEstab 0
SctpActiveEstabs 0
SctpPassiveEstabs 0
SctpAborteds 0
SctpShutdowns 0
[...]
setns(/run/netns/test) ...
/proc/net/sctp/snmp [pid: 175998]
SctpCurrEstab 0
SctpActiveEstabs 0
SctpPassiveEstabs 0
SctpAborteds 0
SctpShutdowns 0
SctpOutOfBlues 0
[...]
-Tommi
View attachment "repro.c" of type "text/x-csrc" (1127 bytes)
Download attachment "iperf-netns" of type "application/x-shellscript" (303 bytes)
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