[PATCH v3] selinux: lsm: fix a missing-check bug in selinux_add_mnt_opt( )

From: Gen Zhang
Date: Thu Jun 06 2019 - 05:27:56 EST


In selinux_add_mnt_opt(), 'val' is allocated by kmemdup_nul(). It returns
NULL when fails. So 'val' should be checked. And 'mnt_opts' should be
freed when error.

Signed-off-by: Gen Zhang <blackgod016574@xxxxxxxxx>
Fixes: 757cbe597fe8 ("LSM: new method: ->sb_add_mnt_opt()")
---
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3ec702c..4e4c1c6 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1052,15 +1052,23 @@ static int selinux_add_mnt_opt(const char *option, const char *val, int len,
if (token == Opt_error)
return -EINVAL;

- if (token != Opt_seclabel)
- val = kmemdup_nul(val, len, GFP_KERNEL);
+ if (token != Opt_seclabel) {
+ val = kmemdup_nul(val, len, GFP_KERNEL);
+ if (!val) {
+ rc = -ENOMEM;
+ goto free_opt;
+ }
+ }
rc = selinux_add_opt(token, val, mnt_opts);
if (unlikely(rc)) {
kfree(val);
- if (*mnt_opts) {
- selinux_free_mnt_opts(*mnt_opts);
- *mnt_opts = NULL;
- }
+ goto free_opt;
+ }
+ return rc;
+free_opt:
+ if (*mnt_opts) {
+ selinux_free_mnt_opts(*mnt_opts);
+ *mnt_opts = NULL;
}
return rc;
}