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Date: Tue, 05 May 2020 18:13:08 +0200
From: Andreas Schwab <schwab@...e.de>
To: Vasily Averin <vvs@...tuozzo.com>
Cc: linux-kernel@...r.kernel.org,
Andrew Morton <akpm@...ux-foundation.org>,
NeilBrown <neilb@...e.com>, Waiman Long <longman@...hat.com>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>,
Peter Oberparleiter <oberpar@...ux.ibm.com>
Subject: Re: [PATCH 7/7] sysvipc_find_ipc should increase position index
I think this is causing this bug (seen on 5.6.8):
# ipcs -q
------ Message Queues --------
key msqid owner perms used-bytes messages
# ipcmk -Q
Message queue id: 0
# ipcs -q
------ Message Queues --------
key msqid owner perms used-bytes messages
0x82db8127 0 root 644 0 0
# ipcmk -Q
Message queue id: 1
# ipcs -q
------ Message Queues --------
key msqid owner perms used-bytes messages
0x82db8127 0 root 644 0 0
0x76d1fb2a 1 root 644 0 0
# ipcrm -q 0
# ipcs -q
------ Message Queues --------
key msqid owner perms used-bytes messages
0x76d1fb2a 1 root 644 0 0
0x76d1fb2a 1 root 644 0 0
# ipcmk -Q
Message queue id: 2
# ipcrm -q 2
# ipcs -q
------ Message Queues --------
key msqid owner perms used-bytes messages
0x76d1fb2a 1 root 644 0 0
0x76d1fb2a 1 root 644 0 0
# ipcmk -Q
Message queue id: 3
# ipcrm -q 1
# ipcs -q
------ Message Queues --------
key msqid owner perms used-bytes messages
0x7c982867 3 root 644 0 0
0x7c982867 3 root 644 0 0
0x7c982867 3 root 644 0 0
0x7c982867 3 root 644 0 0
As you can see, whenever an IPC item with a low id is deleted, the items
with higher ids are duplicated, as if filling a hole.
Andreas.
--
Andreas Schwab, SUSE Labs, schwab@...e.de
GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
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