2019-06-12 17:59:24

by Gen Zhang

Subject: [PATCH v4] selinux: fix a missing-check bug in selinux_add_mnt_opt( )

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 <[email protected]>
Fixes: 757cbe597fe8 ("LSM: new method: ->sb_add_mnt_opt()")
---
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 3ec702c..b4b888e 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -1052,15 +1052,24 @@ 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;
}

2019-06-12 18:06:27

by Paul Moore

Subject: Re: [PATCH v4] selinux: fix a missing-check bug in selinux_add_mnt_opt( )

On Wed, Jun 12, 2019 at 9:28 AM Gen Zhang <[email protected]> wrote:
> 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 <[email protected]>
> Fixes: 757cbe597fe8 ("LSM: new method: ->sb_add_mnt_opt()")
> ---
> diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
> index 3ec702c..b4b888e 100644
> --- a/security/selinux/hooks.c
> +++ b/security/selinux/hooks.c
> @@ -1052,15 +1052,24 @@ 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;
> + }

This block has an extra indent, but I'll go ahead and fix that during
the merge. I have to mention that had you run this patch through
./scripts/checkpatch.pl it would have caught the mistake :)

Regardless, thanks for the patch, I've merged it into the
selinux/stable-5.2 branch and I'll be testing it shortly.

> + }
> 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;
> }

--
paul moore
http://www.paul-moore.com