Regression in 5876aca0484f ("libselinux: free data on selabel open failure")

[Petr Lautrbach <lautrbach@redhat.com>]

Hello,

Katerina Koukiou https://bugzilla.redhat.com/show_bug.cgi?id=2295428
discovered a regression in libselinux [1] which can be demonstrated by
running `matchpathcon` on a system with SELinux disabled and without any
SELinux policy installed.

Fedora reproducer:

$ toolbox create
$ toolbox enter
toolbox$ matchpatchcon /abc

Before 5876aca0484f:

$ matchpathcon /abc
  Error while opening file contexts database: No such file or directory

After 5876aca0484f:

$ matchpathcon /abc
[1]    761709 segmentation fault (core dumped)  matchpathcon /abc

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff7f9a7b8 in closef (rec=0x405a10) at label_file.c:915
warning: Source file is more recent than executable.
915                     free(spec->lr.ctx_trans);
(gdb) bt full
#0  0x00007ffff7f9a7b8 in closef (rec=0x405a10) at label_file.c:915
        data = 0x405a80
        area = 0x6ffffdf48
        last_area = 0x7fffffffdc90
        spec = 0x405
        stem = 0x2
        i = 0
#1  0x00007ffff7f968b7 in selabel_close (rec=0x405a10) at label.c:364
No locals.
#2  0x00007ffff7f9648d in selabel_open (backend=0, opts=0x7fffffffdd80, nopts=6) at label.c:228
        rec = 0x405a10
#3  0x00000000004015e7 in main (argc=2, argv=0x7fffffffdf48) at matchpathcon.c:131
        i = 32767
        force_mode = 0
        header = 1
        opt = -1
        verify = 0
        notrans = 0
        error = 0
        quiet = 0
        hnd = 0x7fffffffde20
        options = {{type = 0, value = 0x0}, {type = 0, value = 0x0}, {type = 0, value = 0x0}, {type = 0, 
            value = 0x0}, {type = 0, value = 0x0}, {type = 0, value = 0x0}}


As a workaround, it's necessary to install SElinux policy

toolbox$ sudo dnf install selinux-policy-targeted
toolbox$ $ matchpathcon /abc                       
/abc    system_u:object_r:etc_runtime_t:s0


[1] https://bugzilla.redhat.com/show_bug.cgi?id=2295428