[v3,18/24] LSM: Use lsmcontext in security_dentry_init_security
diff mbox series

Message ID 20190621185233.6766-19-casey@schaufler-ca.com
State Superseded
Headers show
Series
  • LSM: Module stacking for AppArmor
Related show

Commit Message

Casey Schaufler June 21, 2019, 6:52 p.m. UTC
Change the security_dentry_init_security() interface to
fill an lsmcontext structure instead of a void * data area
and a length. The lone caller of this interface is NFS4,
which may make copies of the data using its own mechanisms.
A rework of the nfs4 code to use the lsmcontext properly
is a significant project, so the coward's way out is taken,
and the lsmcontext data from security_dentry_init_security()
is copied, then released directly.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
---
 fs/nfs/nfs4proc.c        | 26 ++++++++++++++++----------
 include/linux/security.h |  7 +++----
 security/security.c      | 20 ++++++++++++++++----
 3 files changed, 35 insertions(+), 18 deletions(-)

Comments

Kees Cook June 22, 2019, 10:54 p.m. UTC | #1
On Fri, Jun 21, 2019 at 11:52:27AM -0700, Casey Schaufler wrote:
> Change the security_dentry_init_security() interface to
> fill an lsmcontext structure instead of a void * data area
> and a length. The lone caller of this interface is NFS4,
> which may make copies of the data using its own mechanisms.
> A rework of the nfs4 code to use the lsmcontext properly
> is a significant project, so the coward's way out is taken,
> and the lsmcontext data from security_dentry_init_security()
> is copied, then released directly.
> 
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
> ---
>  fs/nfs/nfs4proc.c        | 26 ++++++++++++++++----------
>  include/linux/security.h |  7 +++----
>  security/security.c      | 20 ++++++++++++++++----
>  3 files changed, 35 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index af1c0db29c39..952f805965bb 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -113,6 +113,7 @@ static inline struct nfs4_label *
>  nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
>  	struct iattr *sattr, struct nfs4_label *label)
>  {
> +	struct lsmcontext context;
>  	int err;
>  
>  	if (label == NULL)
> @@ -122,21 +123,26 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
>  		return NULL;
>  
>  	err = security_dentry_init_security(dentry, sattr->ia_mode,
> -				&dentry->d_name, (void **)&label->label, &label->len);
> -	if (err == 0)
> -		return label;
> +					    &dentry->d_name, &context);
> +
> +	if (err)
> +		return NULL;
> +
> +	label->label = kmemdup(context.context, context.len, GFP_KERNEL);
> +	if (label->label == NULL)
> +		label = NULL;
> +	else
> +		label->len = context.len;
> +
> +	security_release_secctx(&context);
> +
> +	return label;
>  
> -	return NULL;
>  }
>  static inline void
>  nfs4_label_release_security(struct nfs4_label *label)
>  {
> -	struct lsmcontext scaff; /* scaffolding */
> -
> -	if (label) {
> -		lsmcontext_init(&scaff, label->label, label->len, 0);
> -		security_release_secctx(&scaff);
> -	}
> +	kfree(label->label);
>  }
>  static inline u32 *nfs4_bitmask(struct nfs_server *server, struct nfs4_label *label)
>  {
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 3cbe43db16f5..2a2785a4e752 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -348,8 +348,8 @@ int security_sb_clone_mnt_opts(const struct super_block *oldsb,
>  int security_add_mnt_opt(const char *option, const char *val,
>  				int len, void **mnt_opts);
>  int security_dentry_init_security(struct dentry *dentry, int mode,
> -					const struct qstr *name, void **ctx,
> -					u32 *ctxlen);
> +					const struct qstr *name,
> +					struct lsmcontext *ctx);
>  int security_dentry_create_files_as(struct dentry *dentry, int mode,
>  					struct qstr *name,
>  					const struct cred *old,
> @@ -720,8 +720,7 @@ static inline void security_inode_free(struct inode *inode)
>  static inline int security_dentry_init_security(struct dentry *dentry,
>  						 int mode,
>  						 const struct qstr *name,
> -						 void **ctx,
> -						 u32 *ctxlen)
> +						 struct lsmcontext *ctx)
>  {
>  	return -EOPNOTSUPP;
>  }
> diff --git a/security/security.c b/security/security.c
> index f461ab3fb9c4..842ac65abc08 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -453,6 +453,8 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
>  		 * secid in the lsmblob structure.
>  		 */
>  		if (hooks[i].head == &security_hook_heads.audit_rule_match ||
> +		    hooks[i].head ==
> +			&security_hook_heads.dentry_init_security ||
>  		    hooks[i].head == &security_hook_heads.kernel_act_as ||
>  		    hooks[i].head ==
>  			&security_hook_heads.socket_getpeersec_dgram ||
> @@ -1040,11 +1042,21 @@ void security_inode_free(struct inode *inode)
>  }
>  
>  int security_dentry_init_security(struct dentry *dentry, int mode,
> -					const struct qstr *name, void **ctx,
> -					u32 *ctxlen)
> +				  const struct qstr *name,
> +				  struct lsmcontext *cp)
>  {
> -	return call_int_hook(dentry_init_security, -EOPNOTSUPP, dentry, mode,
> -				name, ctx, ctxlen);
> +	int *display = current->security;
> +	struct security_hook_list *hp;
> +
> +	hlist_for_each_entry(hp, &security_hook_heads.dentry_init_security,
> +			     list)
> +		if (*display == 0 || *display == hp->slot) {

Is this supposed to be == -1 not 0? Isn't 0 an assigned slot?

Otherwise:

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> +			cp->slot = hp->slot;
> +			return hp->hook.dentry_init_security(dentry, mode,
> +					name, (void **)&cp->context, &cp->len);
> +		}
> +
> +	return -EOPNOTSUPP;
>  }
>  EXPORT_SYMBOL(security_dentry_init_security);
>  
> -- 
> 2.20.1
>
John Johansen June 24, 2019, 9:46 p.m. UTC | #2
On 6/21/19 11:52 AM, Casey Schaufler wrote:
> Change the security_dentry_init_security() interface to
> fill an lsmcontext structure instead of a void * data area
> and a length. The lone caller of this interface is NFS4,
> which may make copies of the data using its own mechanisms.
> A rework of the nfs4 code to use the lsmcontext properly
> is a significant project, so the coward's way out is taken,
> and the lsmcontext data from security_dentry_init_security()
> is copied, then released directly.
> 
> Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>

With the needed fix (below) that Kees already pointed out

Reviewed-by: John Johansen <john.johansen@canonical.com>


> ---
>  fs/nfs/nfs4proc.c        | 26 ++++++++++++++++----------
>  include/linux/security.h |  7 +++----
>  security/security.c      | 20 ++++++++++++++++----
>  3 files changed, 35 insertions(+), 18 deletions(-)
> 
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index af1c0db29c39..952f805965bb 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -113,6 +113,7 @@ static inline struct nfs4_label *
>  nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
>  	struct iattr *sattr, struct nfs4_label *label)
>  {
> +	struct lsmcontext context;
>  	int err;
>  
>  	if (label == NULL)
> @@ -122,21 +123,26 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
>  		return NULL;
>  
>  	err = security_dentry_init_security(dentry, sattr->ia_mode,
> -				&dentry->d_name, (void **)&label->label, &label->len);
> -	if (err == 0)
> -		return label;
> +					    &dentry->d_name, &context);
> +
> +	if (err)
> +		return NULL;
> +
> +	label->label = kmemdup(context.context, context.len, GFP_KERNEL);
> +	if (label->label == NULL)
> +		label = NULL;
> +	else
> +		label->len = context.len;
> +
> +	security_release_secctx(&context);
> +
> +	return label;
>  
> -	return NULL;
>  }
>  static inline void
>  nfs4_label_release_security(struct nfs4_label *label)
>  {
> -	struct lsmcontext scaff; /* scaffolding */
> -
> -	if (label) {
> -		lsmcontext_init(&scaff, label->label, label->len, 0);
> -		security_release_secctx(&scaff);
> -	}
> +	kfree(label->label);
>  }
>  static inline u32 *nfs4_bitmask(struct nfs_server *server, struct nfs4_label *label)
>  {
> diff --git a/include/linux/security.h b/include/linux/security.h
> index 3cbe43db16f5..2a2785a4e752 100644
> --- a/include/linux/security.h
> +++ b/include/linux/security.h
> @@ -348,8 +348,8 @@ int security_sb_clone_mnt_opts(const struct super_block *oldsb,
>  int security_add_mnt_opt(const char *option, const char *val,
>  				int len, void **mnt_opts);
>  int security_dentry_init_security(struct dentry *dentry, int mode,
> -					const struct qstr *name, void **ctx,
> -					u32 *ctxlen);
> +					const struct qstr *name,
> +					struct lsmcontext *ctx);
>  int security_dentry_create_files_as(struct dentry *dentry, int mode,
>  					struct qstr *name,
>  					const struct cred *old,
> @@ -720,8 +720,7 @@ static inline void security_inode_free(struct inode *inode)
>  static inline int security_dentry_init_security(struct dentry *dentry,
>  						 int mode,
>  						 const struct qstr *name,
> -						 void **ctx,
> -						 u32 *ctxlen)
> +						 struct lsmcontext *ctx)
>  {
>  	return -EOPNOTSUPP;
>  }
> diff --git a/security/security.c b/security/security.c
> index f461ab3fb9c4..842ac65abc08 100644
> --- a/security/security.c
> +++ b/security/security.c
> @@ -453,6 +453,8 @@ void __init security_add_hooks(struct security_hook_list *hooks, int count,
>  		 * secid in the lsmblob structure.
>  		 */
>  		if (hooks[i].head == &security_hook_heads.audit_rule_match ||
> +		    hooks[i].head ==
> +			&security_hook_heads.dentry_init_security ||
>  		    hooks[i].head == &security_hook_heads.kernel_act_as ||
>  		    hooks[i].head ==
>  			&security_hook_heads.socket_getpeersec_dgram ||
> @@ -1040,11 +1042,21 @@ void security_inode_free(struct inode *inode)
>  }
>  
>  int security_dentry_init_security(struct dentry *dentry, int mode,
> -					const struct qstr *name, void **ctx,
> -					u32 *ctxlen)
> +				  const struct qstr *name,
> +				  struct lsmcontext *cp)
>  {
> -	return call_int_hook(dentry_init_security, -EOPNOTSUPP, dentry, mode,
> -				name, ctx, ctxlen);
> +	int *display = current->security;
> +	struct security_hook_list *hp;
> +
> +	hlist_for_each_entry(hp, &security_hook_heads.dentry_init_security,
> +			     list)
> +		if (*display == 0 || *display == hp->slot) {
> +			cp->slot = hp->slot;
> +			return hp->hook.dentry_init_security(dentry, mode,
> +					name, (void **)&cp->context, &cp->len);
> +		}
> +

should be
if (*display == LSMBLOB_INVALID || *display == hp->slot)

> +	return -EOPNOTSUPP;
>  }
>  EXPORT_SYMBOL(security_dentry_init_security);
>  
>

Patch
diff mbox series

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index af1c0db29c39..952f805965bb 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -113,6 +113,7 @@  static inline struct nfs4_label *
 nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
 	struct iattr *sattr, struct nfs4_label *label)
 {
+	struct lsmcontext context;
 	int err;
 
 	if (label == NULL)
@@ -122,21 +123,26 @@  nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
 		return NULL;
 
 	err = security_dentry_init_security(dentry, sattr->ia_mode,
-				&dentry->d_name, (void **)&label->label, &label->len);
-	if (err == 0)
-		return label;
+					    &dentry->d_name, &context);
+
+	if (err)
+		return NULL;
+
+	label->label = kmemdup(context.context, context.len, GFP_KERNEL);
+	if (label->label == NULL)
+		label = NULL;
+	else
+		label->len = context.len;
+
+	security_release_secctx(&context);
+
+	return label;
 
-	return NULL;
 }
 static inline void
 nfs4_label_release_security(struct nfs4_label *label)
 {
-	struct lsmcontext scaff; /* scaffolding */
-
-	if (label) {
-		lsmcontext_init(&scaff, label->label, label->len, 0);
-		security_release_secctx(&scaff);
-	}
+	kfree(label->label);
 }
 static inline u32 *nfs4_bitmask(struct nfs_server *server, struct nfs4_label *label)
 {
diff --git a/include/linux/security.h b/include/linux/security.h
index 3cbe43db16f5..2a2785a4e752 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -348,8 +348,8 @@  int security_sb_clone_mnt_opts(const struct super_block *oldsb,
 int security_add_mnt_opt(const char *option, const char *val,
 				int len, void **mnt_opts);
 int security_dentry_init_security(struct dentry *dentry, int mode,
-					const struct qstr *name, void **ctx,
-					u32 *ctxlen);
+					const struct qstr *name,
+					struct lsmcontext *ctx);
 int security_dentry_create_files_as(struct dentry *dentry, int mode,
 					struct qstr *name,
 					const struct cred *old,
@@ -720,8 +720,7 @@  static inline void security_inode_free(struct inode *inode)
 static inline int security_dentry_init_security(struct dentry *dentry,
 						 int mode,
 						 const struct qstr *name,
-						 void **ctx,
-						 u32 *ctxlen)
+						 struct lsmcontext *ctx)
 {
 	return -EOPNOTSUPP;
 }
diff --git a/security/security.c b/security/security.c
index f461ab3fb9c4..842ac65abc08 100644
--- a/security/security.c
+++ b/security/security.c
@@ -453,6 +453,8 @@  void __init security_add_hooks(struct security_hook_list *hooks, int count,
 		 * secid in the lsmblob structure.
 		 */
 		if (hooks[i].head == &security_hook_heads.audit_rule_match ||
+		    hooks[i].head ==
+			&security_hook_heads.dentry_init_security ||
 		    hooks[i].head == &security_hook_heads.kernel_act_as ||
 		    hooks[i].head ==
 			&security_hook_heads.socket_getpeersec_dgram ||
@@ -1040,11 +1042,21 @@  void security_inode_free(struct inode *inode)
 }
 
 int security_dentry_init_security(struct dentry *dentry, int mode,
-					const struct qstr *name, void **ctx,
-					u32 *ctxlen)
+				  const struct qstr *name,
+				  struct lsmcontext *cp)
 {
-	return call_int_hook(dentry_init_security, -EOPNOTSUPP, dentry, mode,
-				name, ctx, ctxlen);
+	int *display = current->security;
+	struct security_hook_list *hp;
+
+	hlist_for_each_entry(hp, &security_hook_heads.dentry_init_security,
+			     list)
+		if (*display == 0 || *display == hp->slot) {
+			cp->slot = hp->slot;
+			return hp->hook.dentry_init_security(dentry, mode,
+					name, (void **)&cp->context, &cp->len);
+		}
+
+	return -EOPNOTSUPP;
 }
 EXPORT_SYMBOL(security_dentry_init_security);