linux-kernel - Re: [PATCH] Smack: Fix memory leak in smack_inode

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Date:   Mon, 4 Jun 2018 14:01:34 -0700
From:   Casey Schaufler <casey@...aufler-ca.com>
To:     "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>, Tejun Heo <tj@...nel.org>
Cc:     chandan.vn@...sung.com,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "bfields@...ldses.org" <bfields@...ldses.org>,
        "jlayton@...nel.org" <jlayton@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        CPGS <cpgs@...sung.com>,
        Sireesha Talluri <sireesha.t@...sung.com>,
        Chris Wright <chrisw@...s-sol.org>
Subject: Re: [PATCH] Smack: Fix memory leak in smack_inode_getsecctx

On 6/1/2018 10:45 AM, Casey Schaufler wrote:
> Fix memory leak in smack_inode_getsecctx
>
> The implementation of smack_inode_getsecctx() made
> incorrect assumptions about how Smack presents a security
> context. Smack does not need to allocate memory to support
> security contexts, so "releasing" a Smack context is a no-op.
> The code made an unnecessary copy and returned that as a
> context, which was never freed. The revised implementation
> returns the context correctly.
>
> Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>

Tejun, does this pass your tests?

> ---
>  security/smack/smack_lsm.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/security/smack/smack_lsm.c b/security/smack/smack_lsm.c
> index 0b414836bebd..5e3beae334a8 100644
> --- a/security/smack/smack_lsm.c
> +++ b/security/smack/smack_lsm.c
> @@ -1545,9 +1545,9 @@ static int smack_inode_listsecurity(struct inode *inode, char *buffer,
>   */
>  static void smack_inode_getsecid(struct inode *inode, u32 *secid)
>  {
> -	struct inode_smack *isp = inode->i_security;
> +	struct smack_known *skp = smk_of_inode(inode);
>  
> -	*secid = isp->smk_inode->smk_secid;
> +	*secid = skp->smk_secid;
>  }
>  
>  /*
> @@ -4538,12 +4538,10 @@ static int smack_inode_setsecctx(struct dentry *dentry, void *ctx, u32 ctxlen)
>  
>  static int smack_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen)
>  {
> -	int len = 0;
> -	len = smack_inode_getsecurity(inode, XATTR_SMACK_SUFFIX, ctx, true);
> +	struct smack_known *skp = smk_of_inode(inode);
>  
> -	if (len < 0)
> -		return len;
> -	*ctxlen = len;
> +	*ctx = skp->smk_known;
> +	*ctxlen = strlen(skp->smk_known);
>  	return 0;
>  }
>  
>
> --
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