lixinyunandAlejandro Colomar
10429edc14
Groupmod -U may cause crashes because of double free. If without -a, the first free of (*ogrp).gr_mem is in gr_free_members(&grp), and then in gr_update without -n or gr_remove with -n.
Considering the minimal impact of modifications on existing code, delete gr_free_members(&grp) to avoid double free.Although this may seem reckless, the second free in two different positions will definitely be triggered, and the following two test cases can be used to illustrate the situation :
[root@localhost src]# ./useradd u1
[root@localhost src]# ./useradd u2
[root@localhost src]# ./useradd u3
[root@localhost src]# ./groupadd -U u1,u2,u3 g1
[root@localhost src]# ./groupmod -n g2 -U u1,u2 g1
Segmentation fault
This case would free (*ogrp).gr_mem in gr_free_members(&grp) due to assignment statements grp = *ogrp, then in if (nflg && (gr_remove (group_name) == 0)), which finally calls gr_free_members(grent) to free (*ogrp).gr_mem again.
[root@localhost src]# ./useradd u1
[root@localhost src]# ./useradd u2
[root@localhost src]# ./useradd u3
[root@localhost src]# ./groupadd -U u1,u2,u3 g1
[root@localhost src]# ./groupmod -U u1,u2 g1
Segmentation fault
The other case would free (*ogrp).gr_mem in gr_free_members(&grp) too, then in if (gr_update (&grp) == 0), which finally calls gr_free_members(grent) too to free (*ogrp).gr_mem again.
So the first free is unnecessary, maybe we can drop it.
Fixes: 342c934a35 ("add -U option to groupadd and groupmod")
Closes: <https://github.com/shadow-maint/shadow/issues/1013>
Link: <https://github.com/shadow-maint/shadow/pull/1007>
Link: <https://github.com/shadow-maint/shadow/pull/271>
Link: <https://github.com/shadow-maint/shadow/issues/265>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Reviewed-by: Alejandro Colomar <alx@kernel.org>
Signed-off-by: lixinyun <li.xinyun@h3c.com>
shadow-utils
Introduction
The shadow-utils package includes the necessary programs for converting UNIX password files to the shadow password format, plus programs for managing user and group accounts. The pwconv command converts passwords to the shadow password format. The pwunconv command unconverts shadow passwords and generates a passwd file (a standard UNIX password file). The pwck command checks the integrity of password and shadow files. The lastlog command prints out the last login times for all users. The useradd, userdel, and usermod commands are used for managing user accounts. The groupadd, groupdel, and groupmod commands are used for managing group accounts.
Sites
Code
The main development branch is at https://github.com/shadow-maint/shadow.git
See STABLE.md for a list of supported stable branches.
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