2021-12-10 12:04:16

by 赵军奎

Subject: [PATCH v3] security/selinux: fix potential memleak in error branch

This patch try to fix potential memleak in error branch.

Signed-off-by: Bernard Zhao <[email protected]>

Changes since V1:
*make it to be simpler to do the "(!s)" check before the "(!opts)" check.

Changes since v2:
*add *mnt_opts = NULL after kfree(opt) to avoid double free risk.
---
security/selinux/hooks.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 62d30c0a30c2..0d018f054dfb 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -983,18 +983,22 @@ static int selinux_sb_clone_mnt_opts(const struct super_block *oldsb,
static int selinux_add_opt(int token, const char *s, void **mnt_opts)
{
struct selinux_mnt_opts *opts = *mnt_opts;
+ bool is_alloc_opts = false;

if (token == Opt_seclabel) /* eaten and completely ignored */
return 0;

+ if (!s)
+ return -ENOMEM;
+
if (!opts) {
opts = kzalloc(sizeof(struct selinux_mnt_opts), GFP_KERNEL);
if (!opts)
return -ENOMEM;
*mnt_opts = opts;
+ is_alloc_opts = true;
}
- if (!s)
- return -ENOMEM;
+
switch (token) {
case Opt_context:
if (opts->context || opts->defcontext)
@@ -1019,6 +1023,10 @@ static int selinux_add_opt(int token, const char *s, void **mnt_opts)
}
return 0;
Einval:
+ if (is_alloc_opts) {
+ kfree(opts);
+ *mnt_opts = NULL;
+ }
pr_warn(SEL_MOUNT_FAIL_MSG);
return -EINVAL;
}
--
2.33.1

2021-12-21 20:00:35

by Paul Moore

Subject: Re: [PATCH v3] security/selinux: fix potential memleak in error branch

On Fri, Dec 10, 2021 at 7:04 AM Bernard Zhao <[email protected]> wrote:
>
> This patch try to fix potential memleak in error branch.
>
> Signed-off-by: Bernard Zhao <[email protected]>
>
> Changes since V1:
> *make it to be simpler to do the "(!s)" check before the "(!opts)" check.
>
> Changes since v2:
> *add *mnt_opts = NULL after kfree(opt) to avoid double free risk.
> ---
> security/selinux/hooks.c | 12 ++++++++++--
> 1 file changed, 10 insertions(+), 2 deletions(-)

Hi Bernard,

I apologize for the late response, this was lost in my inbox for some
reason. Regardless, this looks fine to me so I'm merging it into
selinux/next; thanks for your help.

However, Ondrej made a few good suggestions about further improvements
that could be made up at the LSM layer, I think it would be nice if
you could look into that too.

Thanks again for your help.

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