[PATCH] libselinux: set free'd data to NULL

[Petr Lautrbach <lautrbach@xxxxxxxxxx>]

Fixes segfault in selabel_open() on systems with SELinux disabled and without any
SELinux policy installed introduced by commit 5876aca0484f ("libselinux: free
data on selabel open failure"):

    $ sestatus
    SELinux status:                 disabled

    $ cat /etc/selinux/config
    cat: /etc/selinux/config: No such file or directory

    $ matchpathcon /abc
    [1]    907999 segmentation fault (core dumped)  matchpathcon /abc

Signed-off-by: Petr Lautrbach <lautrbach@xxxxxxxxxx>
---
 libselinux/src/label_backends_android.c | 1 +
 libselinux/src/label_file.c             | 1 +
 libselinux/src/label_media.c            | 1 +
 libselinux/src/label_x.c                | 1 +
 4 files changed, 4 insertions(+)

diff --git a/libselinux/src/label_backends_android.c b/libselinux/src/label_backends_android.c
index 49a87686de4c..5bad24f20d73 100644
--- a/libselinux/src/label_backends_android.c
+++ b/libselinux/src/label_backends_android.c
@@ -260,6 +260,7 @@ static void closef(struct selabel_handle *rec)
 		free(data->spec_arr);
 
 	free(data);
+	rec->data = NULL;
 }
 
 static struct selabel_lookup_rec *property_lookup(struct selabel_handle *rec,
diff --git a/libselinux/src/label_file.c b/libselinux/src/label_file.c
index 2732972e61cf..59c9f2ef3442 100644
--- a/libselinux/src/label_file.c
+++ b/libselinux/src/label_file.c
@@ -942,6 +942,7 @@ static void closef(struct selabel_handle *rec)
 		free(last_area);
 	}
 	free(data);
+	rec->data = NULL;
 }
 
 // Finds all the matches of |key| in the given context. Returns the result in
diff --git a/libselinux/src/label_media.c b/libselinux/src/label_media.c
index 852aeada8ff4..bae065c12a55 100644
--- a/libselinux/src/label_media.c
+++ b/libselinux/src/label_media.c
@@ -183,6 +183,7 @@ static void close(struct selabel_handle *rec)
 	    free(spec_arr);
 
 	free(data);
+	rec->data = NULL;
 }
 
 static struct selabel_lookup_rec *lookup(struct selabel_handle *rec,
diff --git a/libselinux/src/label_x.c b/libselinux/src/label_x.c
index a8decc7a0093..ddae4f6c22b6 100644
--- a/libselinux/src/label_x.c
+++ b/libselinux/src/label_x.c
@@ -210,6 +210,7 @@ static void close(struct selabel_handle *rec)
 	    free(spec_arr);
 
 	free(data);
+	rec->data = NULL;
 }
 
 static struct selabel_lookup_rec *lookup(struct selabel_handle *rec,
-- 
2.45.2