GNU bug report logs - #65617
coreutils 9.4: seg.fault in readutmp with systemd

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Paul Eggert <eggert <at> cs.ucla.edu>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#65617: closed (coreutils 9.4: seg.fault in readutmp with systemd)
Date: Thu, 31 Aug 2023 01:30:02 +0000

[Message part 1 (text/plain, inline)]

Your message dated Wed, 30 Aug 2023 18:29:09 -0700
with message-id <474722d1-d314-09b1-9302-2c920a8bed12 <at> cs.ucla.edu>
and subject line Re: bug#65617: coreutils 9.4: seg.fault in readutmp with systemd
has caused the debbugs.gnu.org bug report #65617,
regarding coreutils 9.4: seg.fault in readutmp with systemd
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


-- 
65617: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=65617
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Thorsten Kukuk <kukuk <at> suse.com>
To: bug-coreutils <at> gnu.org
Subject: coreutils 9.4: seg.fault in readutmp with systemd
Date: Wed, 30 Aug 2023 11:21:06 +0000

coreutils 9.4 with the --enable-systemd option seg.faults in
lib/readutmp.c, line 801:

for (session_ptr = sessions; *session_ptr != NULL; session_ptr++)

If there is no session, "sessions" is NULL and "*session_ptr" will
dereference a NULL pointer.
Affected are who, pinky and uptime.

A simple fix:

diff --git a/lib/readutmp.c b/lib/readutmp.c
index 0173b7e0c1..e99158677c 100644
--- a/lib/readutmp.c
+++ b/lib/readutmp.c
@@ -795,7 +795,7 @@ read_utmp_from_systemd (idx_t *n_entries, STRUCT_UTMP **utmp_buf, int options)
     {
       char **sessions;
       int num_sessions = sd_get_sessions (&sessions);
-      if (num_sessions >= 0)
+      if (num_sessions > 0)
         {
           char **session_ptr;
           for (session_ptr = sessions; *session_ptr != NULL; session_ptr++)


-- 
Thorsten Kukuk, Distinguished Engineer, Senior Architect, Future Technologies
SUSE Software Solutions Germany GmbH, Frankenstraße 146, 90461 Nuernberg, Germany
Managing Director: Ivo Totev, Andrew McDonald, Werner Knoblich
(HRB 36809, AG Nürnberg)

[Message part 3 (message/rfc822, inline)]

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Thorsten Kukuk <kukuk <at> suse.com>
Cc: 65617-done <at> debbugs.gnu.org, Gnulib bugs <bug-gnulib <at> gnu.org>
Subject: Re: bug#65617: coreutils 9.4: seg.fault in readutmp with systemd
Date: Wed, 30 Aug 2023 18:29:09 -0700

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Thanks for reporting that. I installed the attached patch into Gnulib 
and this should appear in the next coreutils release.

[0001-readutmp-fix-core-dump-if-enable-systemd.patch (text/x-patch, attachment)]

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