[PATCH] lsm,nfs: fix memory leak of lsm_context

[Casey Schaufler]

On 2/20/2025 11:29 AM, Stephen Smalley wrote:
> commit b530104f50e8 ("lsm: lsm_context in security_dentry_init_security")
> did not preserve the lsm id for subsequent release calls, which results
> in a memory leak. Fix it by saving the lsm id in the nfs4_label and
> providing it on the subsequent release call.
>
> Fixes: b530104f50e8 ("lsm: lsm_context in security_dentry_init_security")
> Signed-off-by: Stephen Smalley <stephen.smalley.work at gmail.com>

Please don't accept this. I will have a better, simpler, more appropriate
fix promptly.

> ---
>  fs/nfs/nfs4proc.c    | 7 ++++---
>  include/linux/nfs4.h | 1 +
>  2 files changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index df9669d4ded7..c0caaec7bd20 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -133,6 +133,7 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
>  	if (err)
>  		return NULL;
>  
> +	label->lsmid = shim.id;
>  	label->label = shim.context;
>  	label->len = shim.len;
>  	return label;
> @@ -145,7 +146,7 @@ nfs4_label_release_security(struct nfs4_label *label)
>  	if (label) {
>  		shim.context = label->label;
>  		shim.len = label->len;
> -		shim.id = LSM_ID_UNDEF;
> +		shim.id = label->lsmid;
>  		security_release_secctx(&shim);
>  	}
>  }
> @@ -6269,7 +6270,7 @@ static int _nfs4_get_security_label(struct inode *inode, void *buf,
>  					size_t buflen)
>  {
>  	struct nfs_server *server = NFS_SERVER(inode);
> -	struct nfs4_label label = {0, 0, buflen, buf};
> +	struct nfs4_label label = {0, 0, 0, buflen, buf};
>  
>  	u32 bitmask[3] = { 0, 0, FATTR4_WORD2_SECURITY_LABEL };
>  	struct nfs_fattr fattr = {
> @@ -6374,7 +6375,7 @@ static int nfs4_do_set_security_label(struct inode *inode,
>  static int
>  nfs4_set_security_label(struct inode *inode, const void *buf, size_t buflen)
>  {
> -	struct nfs4_label ilabel = {0, 0, buflen, (char *)buf };
> +	struct nfs4_label ilabel = {0, 0, 0, buflen, (char *)buf };
>  	struct nfs_fattr *fattr;
>  	int status;
>  
> diff --git a/include/linux/nfs4.h b/include/linux/nfs4.h
> index 71fbebfa43c7..9ac83ca88326 100644
> --- a/include/linux/nfs4.h
> +++ b/include/linux/nfs4.h
> @@ -47,6 +47,7 @@ struct nfs4_acl {
>  struct nfs4_label {
>  	uint32_t	lfs;
>  	uint32_t	pi;
> +	u32		lsmid;
>  	u32		len;
>  	char	*label;
>  };