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From: "Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>
To: Karel Zak <kzak@redhat.com>
Cc: mtk.manpages@gmail.com, util-linux@vger.kernel.org,
	Sami Kerola <kerolasa@iki.fi>
Subject: [PATCH] ipcs.1: ipcs no longer needs read permission on IPC resources
Date: Sat, 16 May 2020 10:10:27 +0200
Message-ID: <5700d4b6-c499-0881-263c-7df96df511ff@gmail.com> (raw)

From: Michael Kerrisk <mtk.manpages@gmail.com>
Date: Sat, 16 May 2020 09:45:11 +0200
Subject: [PATCH] ipcs.1: ipcs no longer needs read permission on IPC resources

With changes starting around util-linux commit 058e81540fbb0d2b78
that switched from using IPC_STAT to parsing /proc/sysvipc/*,
ipcs now shows all IPC objects rather than just the objects for
which the user has read permission. Update the page to reflect this
fact, and also add a NOTES section describing the historical and
fallback behavior where /proc is not available.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
 sys-utils/ipcs.1 | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/sys-utils/ipcs.1 b/sys-utils/ipcs.1
index 93c35e323..4b3baaaa5 100644
--- a/sys-utils/ipcs.1
+++ b/sys-utils/ipcs.1
@@ -8,8 +8,7 @@ ipcs \- show information on IPC facilities
 .B ipcs
-shows information on the inter-process communication facilities
-for which the calling process has read access.
+shows information on inter-process communication facilities.
 By default it shows information about all three resources:
 shared memory segments, message queues, and semaphore arrays.
@@ -76,6 +75,25 @@ Print sizes in bytes.
 .B \-\-human
 Print sizes in human-readable format.
+The current implementation of
+.B ipcs
+obtains information about available IPC resources by parsing the files in
+.IR /proc/sysvipc .
+Before util-linux version v2.23, an alternate mechanism was used: the
+command of
+.BR msgctl (2),
+.BR semctl (2),
+.BR shmctl (2).
+This mechanism is also used in later util-linux versions in the case where
+.I /proc
+is unavailable.
+A limitation of the
+mechanism is that it can only be used to retrieve information about
+IPC resources for which the user has read permission.
 .BR ipcmk (1),
 .BR ipcrm (1),

Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/

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Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-16  8:10 Michael Kerrisk (man-pages) [this message]
2020-05-18 11:41 ` Karel Zak

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