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From: Casey Schaufler <casey@schaufler-ca.com>
To: casey@schaufler-ca.com,
	paul@paul-moore.com,
	linux-security-module@vger.kernel.org
Cc: jmorris@namei.org,
	serge@hallyn.com,
	keescook@chromium.org,
	john.johansen@canonical.com,
	penguin-kernel@i-love.sakura.ne.jp,
	stephen.smalley.work@gmail.com,
	linux-kernel@vger.kernel.org,
	mic@digikod.net,
	ceph-devel@vger.kernel.org,
	linux-nfs@vger.kernel.org
Subject: [PATCH v39 20/42] LSM: Use lsmcontext in security_dentry_init_security
Date: Fri, 15 Dec 2023 14:16:14 -0800
Message-ID: <20231215221636.105680-21-casey@schaufler-ca.com>
In-Reply-To: <20231215221636.105680-1-casey@schaufler-ca.com>
References: <20231215221636.105680-1-casey@schaufler-ca.com>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

Replace the (secctx,seclen) pointer pair with a single
lsmcontext pointer to allow return of the LSM identifier
along with the context and context length. This allows
security_release_secctx() to know how to release the
context. Callers have been modified to use or save the
returned data from the new structure.

Special care is taken in the NFS code, which uses the
same data structure for its own copied labels as it does
for the data which comes from security_dentry_init_security().
In the case of copied labels the data has to be freed, not
released.

Signed-off-by: Casey Schaufler <casey@schaufler-ca.com>
Cc: ceph-devel@vger.kernel.org
Cc: linux-nfs@vger.kernel.org
---
 fs/ceph/super.h               |  3 +--
 fs/ceph/xattr.c               | 19 ++++++-------------
 fs/fuse/dir.c                 | 35 ++++++++++++++++++-----------------
 fs/nfs/dir.c                  |  2 +-
 fs/nfs/inode.c                | 17 ++++++++++-------
 fs/nfs/internal.h             |  8 +++++---
 fs/nfs/nfs4proc.c             | 22 +++++++++-------------
 fs/nfs/nfs4xdr.c              | 22 ++++++++++++----------
 include/linux/lsm_hook_defs.h |  2 +-
 include/linux/nfs4.h          |  8 ++++----
 include/linux/nfs_fs.h        |  2 +-
 include/linux/security.h      |  7 +++----
 security/security.c           |  9 ++++-----
 security/selinux/hooks.c      |  9 +++++----
 14 files changed, 80 insertions(+), 85 deletions(-)

diff --git a/fs/ceph/super.h b/fs/ceph/super.h
index fe0f64a0acb2..d503cc7478b7 100644
--- a/fs/ceph/super.h
+++ b/fs/ceph/super.h
@@ -1133,8 +1133,7 @@ struct ceph_acl_sec_ctx {
 	void *acl;
 #endif
 #ifdef CONFIG_CEPH_FS_SECURITY_LABEL
-	void *sec_ctx;
-	u32 sec_ctxlen;
+	struct lsmcontext lsmctx;
 #endif
 #ifdef CONFIG_FS_ENCRYPTION
 	struct ceph_fscrypt_auth *fscrypt_auth;
diff --git a/fs/ceph/xattr.c b/fs/ceph/xattr.c
index 113956d386c0..4c767a20ac4c 100644
--- a/fs/ceph/xattr.c
+++ b/fs/ceph/xattr.c
@@ -1383,8 +1383,7 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode,
 	int err;
 
 	err = security_dentry_init_security(dentry, mode, &dentry->d_name,
-					    &name, &as_ctx->sec_ctx,
-					    &as_ctx->sec_ctxlen);
+					    &name, &as_ctx->lsmctx);
 	if (err < 0) {
 		WARN_ON_ONCE(err != -EOPNOTSUPP);
 		err = 0; /* do nothing */
@@ -1409,7 +1408,7 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode,
 	 */
 	name_len = strlen(name);
 	err = ceph_pagelist_reserve(pagelist,
-				    4 * 2 + name_len + as_ctx->sec_ctxlen);
+				    4 * 2 + name_len + as_ctx->lsmctx.len);
 	if (err)
 		goto out;
 
@@ -1429,11 +1428,9 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode,
 		as_ctx->pagelist = pagelist;
 	}
 
-	ceph_pagelist_encode_32(pagelist, name_len);
-	ceph_pagelist_append(pagelist, name, name_len);
-
-	ceph_pagelist_encode_32(pagelist, as_ctx->sec_ctxlen);
-	ceph_pagelist_append(pagelist, as_ctx->sec_ctx, as_ctx->sec_ctxlen);
+	ceph_pagelist_encode_32(pagelist, as_ctx->lsmctx.len);
+	ceph_pagelist_append(pagelist, as_ctx->lsmctx.context,
+			     as_ctx->lsmctx.len);
 
 	err = 0;
 out:
@@ -1446,16 +1443,12 @@ int ceph_security_init_secctx(struct dentry *dentry, umode_t mode,
 
 void ceph_release_acl_sec_ctx(struct ceph_acl_sec_ctx *as_ctx)
 {
-#ifdef CONFIG_CEPH_FS_SECURITY_LABEL
-	struct lsmcontext scaff; /* scaffolding */
-#endif
 #ifdef CONFIG_CEPH_FS_POSIX_ACL
 	posix_acl_release(as_ctx->acl);
 	posix_acl_release(as_ctx->default_acl);
 #endif
 #ifdef CONFIG_CEPH_FS_SECURITY_LABEL
-	lsmcontext_init(&scaff, as_ctx->sec_ctx, as_ctx->sec_ctxlen, 0);
-	security_release_secctx(&scaff);
+	security_release_secctx(&as_ctx->lsmctx);
 #endif
 #ifdef CONFIG_FS_ENCRYPTION
 	kfree(as_ctx->fscrypt_auth);
diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index d19cbf34c634..ee24797842df 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -462,29 +462,29 @@ static int get_security_context(struct dentry *entry, umode_t mode,
 {
 	struct fuse_secctx *fctx;
 	struct fuse_secctx_header *header;
-	void *ctx = NULL, *ptr;
-	u32 ctxlen, total_len = sizeof(*header);
+	struct lsmcontext lsmctx = { };
+	void *ptr;
+	u32 total_len = sizeof(*header);
 	int err, nr_ctx = 0;
-	const char *name;
+	const char *name = NULL;
 	size_t namelen;
 
 	err = security_dentry_init_security(entry, mode, &entry->d_name,
-					    &name, &ctx, &ctxlen);
-	if (err) {
-		if (err != -EOPNOTSUPP)
-			goto out_err;
-		/* No LSM is supporting this security hook. Ignore error */
-		ctxlen = 0;
-		ctx = NULL;
-	}
+					    &name, &lsmctx);
+
+	/* If no LSM is supporting this security hook ignore error */
+	if (err && err != -EOPNOTSUPP)
+		goto out_err;
 
-	if (ctxlen) {
+	if (lsmctx.len) {
 		nr_ctx = 1;
 		namelen = strlen(name) + 1;
 		err = -EIO;
-		if (WARN_ON(namelen > XATTR_NAME_MAX + 1 || ctxlen > S32_MAX))
+		if (WARN_ON(namelen > XATTR_NAME_MAX + 1 ||
+		    lsmctx.len > S32_MAX))
 			goto out_err;
-		total_len += FUSE_REC_ALIGN(sizeof(*fctx) + namelen + ctxlen);
+		total_len += FUSE_REC_ALIGN(sizeof(*fctx) + namelen +
+					    lsmctx.len);
 	}
 
 	err = -ENOMEM;
@@ -497,19 +497,20 @@ static int get_security_context(struct dentry *entry, umode_t mode,
 	ptr += sizeof(*header);
 	if (nr_ctx) {
 		fctx = ptr;
-		fctx->size = ctxlen;
+		fctx->size = lsmctx.len;
 		ptr += sizeof(*fctx);
 
 		strcpy(ptr, name);
 		ptr += namelen;
 
-		memcpy(ptr, ctx, ctxlen);
+		memcpy(ptr, lsmctx.context, lsmctx.len);
 	}
 	ext->size = total_len;
 	ext->value = header;
 	err = 0;
 out_err:
-	kfree(ctx);
+	if (nr_ctx)
+		security_release_secctx(&lsmctx);
 	return err;
 }
 
diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 13dffe4201e6..c56a7caea6d3 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -807,7 +807,7 @@ static int nfs_readdir_entry_decode(struct nfs_readdir_descriptor *desc,
 	int ret;
 
 	if (entry->fattr->label)
-		entry->fattr->label->len = NFS4_MAXLABELLEN;
+		entry->fattr->label->lsmctx.len = NFS4_MAXLABELLEN;
 	ret = xdr_decode(desc, entry, stream);
 	if (ret || !desc->plus)
 		return ret;
diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index ebb8d60e1152..ddd8f7bae5de 100644
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -357,14 +357,15 @@ void nfs_setsecurity(struct inode *inode, struct nfs_fattr *fattr)
 		return;
 
 	if ((fattr->valid & NFS_ATTR_FATTR_V4_SECURITY_LABEL) && inode->i_security) {
-		error = security_inode_notifysecctx(inode, fattr->label->label,
-				fattr->label->len);
+		error = security_inode_notifysecctx(inode,
+						fattr->label->lsmctx.context,
+						fattr->label->lsmctx.len);
 		if (error)
 			printk(KERN_ERR "%s() %s %d "
 					"security_inode_notifysecctx() %d\n",
 					__func__,
-					(char *)fattr->label->label,
-					fattr->label->len, error);
+					(char *)fattr->label->lsmctx.context,
+					fattr->label->lsmctx.len, error);
 		nfs_clear_label_invalid(inode);
 	}
 }
@@ -380,12 +381,14 @@ struct nfs4_label *nfs4_label_alloc(struct nfs_server *server, gfp_t flags)
 	if (label == NULL)
 		return ERR_PTR(-ENOMEM);
 
-	label->label = kzalloc(NFS4_MAXLABELLEN, flags);
-	if (label->label == NULL) {
+	label->lsmctx.context = kzalloc(NFS4_MAXLABELLEN, flags);
+	if (label->lsmctx.context == NULL) {
 		kfree(label);
 		return ERR_PTR(-ENOMEM);
 	}
-	label->len = NFS4_MAXLABELLEN;
+	label->lsmctx.len = NFS4_MAXLABELLEN;
+	/* Use an invalid LSM ID as this should never be "released". */
+	label->lsmctx.id = LSM_ID_UNDEF;
 
 	return label;
 }
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 9c9cf764f600..1bc7cdf52f04 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -346,13 +346,15 @@ nfs4_label_copy(struct nfs4_label *dst, struct nfs4_label *src)
 	if (!dst || !src)
 		return NULL;
 
-	if (src->len > NFS4_MAXLABELLEN)
+	if (src->lsmctx.len > NFS4_MAXLABELLEN)
 		return NULL;
 
 	dst->lfs = src->lfs;
 	dst->pi = src->pi;
-	dst->len = src->len;
-	memcpy(dst->label, src->label, src->len);
+	/* Use an invalid LSM ID as lsmctx should never be "released" */
+	dst->lsmctx.id = LSM_ID_UNDEF;
+	dst->lsmctx.len = src->lsmctx.len;
+	memcpy(dst->lsmctx.context, src->lsmctx.context, src->lsmctx.len);
 
 	return dst;
 }
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 6ea99e2aabf3..79626ce7cecd 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -124,12 +124,11 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
 
 	label->lfs = 0;
 	label->pi = 0;
-	label->len = 0;
-	label->label = NULL;
+	label->lsmctx.len = 0;
+	label->lsmctx.context = NULL;
 
 	err = security_dentry_init_security(dentry, sattr->ia_mode,
-				&dentry->d_name, NULL,
-				(void **)&label->label, &label->len);
+				&dentry->d_name, NULL, &label->lsmctx);
 	if (err == 0)
 		return label;
 
@@ -138,12 +137,8 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
 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);
-	}
+	if (label)
+		security_release_secctx(&label->lsmctx);
 }
 static inline u32 *nfs4_bitmask(struct nfs_server *server, struct nfs4_label *label)
 {
@@ -6155,7 +6150,7 @@ 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, {buf, buflen, -1} };
 
 	u32 bitmask[3] = { 0, 0, FATTR4_WORD2_SECURITY_LABEL };
 	struct nfs_fattr fattr = {
@@ -6183,7 +6178,7 @@ static int _nfs4_get_security_label(struct inode *inode, void *buf,
 		return ret;
 	if (!(fattr.valid & NFS_ATTR_FATTR_V4_SECURITY_LABEL))
 		return -ENOENT;
-	return label.len;
+	return label.lsmctx.len;
 }
 
 static int nfs4_get_security_label(struct inode *inode, void *buf,
@@ -6260,7 +6255,8 @@ 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,
+				    {(char *)buf, buflen, -1}};
 	struct nfs_fattr *fattr;
 	int status;
 
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index deec76cf5afe..fe6d184ff169 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -1154,7 +1154,7 @@ static void encode_attrs(struct xdr_stream *xdr, const struct iattr *iap,
 	}
 
 	if (label && (attrmask[2] & FATTR4_WORD2_SECURITY_LABEL)) {
-		len += 4 + 4 + 4 + (XDR_QUADLEN(label->len) << 2);
+		len += 4 + 4 + 4 + (XDR_QUADLEN(label->lsmctx.len) << 2);
 		bmval[2] |= FATTR4_WORD2_SECURITY_LABEL;
 	}
 
@@ -1186,8 +1186,9 @@ static void encode_attrs(struct xdr_stream *xdr, const struct iattr *iap,
 	if (label && (bmval[2] & FATTR4_WORD2_SECURITY_LABEL)) {
 		*p++ = cpu_to_be32(label->lfs);
 		*p++ = cpu_to_be32(label->pi);
-		*p++ = cpu_to_be32(label->len);
-		p = xdr_encode_opaque_fixed(p, label->label, label->len);
+		*p++ = cpu_to_be32(label->lsmctx.len);
+		p = xdr_encode_opaque_fixed(p, label->lsmctx.context,
+					    label->lsmctx.len);
 	}
 	if (bmval[2] & FATTR4_WORD2_MODE_UMASK) {
 		*p++ = cpu_to_be32(iap->ia_mode & S_IALLUGO);
@@ -4236,11 +4237,11 @@ static int decode_attr_security_label(struct xdr_stream *xdr, uint32_t *bitmap,
 			return -EIO;
 		bitmap[2] &= ~FATTR4_WORD2_SECURITY_LABEL;
 		if (len < NFS4_MAXLABELLEN) {
-			if (label && label->len) {
-				if (label->len < len)
+			if (label && label->lsmctx.len) {
+				if (label->lsmctx.len < len)
 					return -ERANGE;
-				memcpy(label->label, p, len);
-				label->len = len;
+				memcpy(label->lsmctx.context, p, len);
+				label->lsmctx.len = len;
 				label->pi = pi;
 				label->lfs = lfs;
 				status = NFS_ATTR_FATTR_V4_SECURITY_LABEL;
@@ -4248,10 +4249,11 @@ static int decode_attr_security_label(struct xdr_stream *xdr, uint32_t *bitmap,
 		} else
 			printk(KERN_WARNING "%s: label too long (%u)!\n",
 					__func__, len);
-		if (label && label->label)
+		if (label && label->lsmctx.context)
 			dprintk("%s: label=%.*s, len=%d, PI=%d, LFS=%d\n",
-				__func__, label->len, (char *)label->label,
-				label->len, label->pi, label->lfs);
+				__func__, label->lsmctx.len,
+				(char *)label->lsmctx.context,
+				label->lsmctx.len, label->pi, label->lfs);
 	}
 	return status;
 }
diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h
index f2bbce7fb28e..741bbf5df0af 100644
--- a/include/linux/lsm_hook_defs.h
+++ b/include/linux/lsm_hook_defs.h
@@ -83,7 +83,7 @@ LSM_HOOK(int, 0, move_mount, const struct path *from_path,
 	 const struct path *to_path)
 LSM_HOOK(int, -EOPNOTSUPP, dentry_init_security, struct dentry *dentry,
 	 int mode, const struct qstr *name, const char **xattr_name,
-	 void **ctx, u32 *ctxlen)
+	 struct lsmcontext *cp)
 LSM_HOOK(int, 0, dentry_create_files_as, struct dentry *dentry, int mode,
 	 struct qstr *name, const struct cred *old, struct cred *new)
 
diff --git a/include/linux/nfs4.h b/include/linux/nfs4.h
index c11c4db34639..04e4afc8deb5 100644
--- a/include/linux/nfs4.h
+++ b/include/linux/nfs4.h
@@ -15,6 +15,7 @@
 
 #include <linux/list.h>
 #include <linux/uidgid.h>
+#include <linux/security.h>
 #include <uapi/linux/nfs4.h>
 #include <linux/sunrpc/msg_prot.h>
 
@@ -44,10 +45,9 @@ struct nfs4_acl {
 #define NFS4_MAXLABELLEN	2048
 
 struct nfs4_label {
-	uint32_t	lfs;
-	uint32_t	pi;
-	u32		len;
-	char	*label;
+	uint32_t		lfs;
+	uint32_t		pi;
+	struct lsmcontext	lsmctx;
 };
 
 typedef struct { char data[NFS4_VERIFIER_SIZE]; } nfs4_verifier;
diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h
index 279262057a92..c314fb43547f 100644
--- a/include/linux/nfs_fs.h
+++ b/include/linux/nfs_fs.h
@@ -457,7 +457,7 @@ static inline void nfs4_label_free(struct nfs4_label *label)
 {
 #ifdef CONFIG_NFS_V4_SECURITY_LABEL
 	if (label) {
-		kfree(label->label);
+		kfree(label->lsmctx.context);
 		kfree(label);
 	}
 #endif
diff --git a/include/linux/security.h b/include/linux/security.h
index dbbfbcfbb299..35604f43d4ff 100644
--- a/include/linux/security.h
+++ b/include/linux/security.h
@@ -404,8 +404,8 @@ int security_sb_clone_mnt_opts(const struct super_block *oldsb,
 int security_move_mount(const struct path *from_path, const struct path *to_path);
 int security_dentry_init_security(struct dentry *dentry, int mode,
 				  const struct qstr *name,
-				  const char **xattr_name, void **ctx,
-				  u32 *ctxlen);
+				  const char **xattr_name,
+				  struct lsmcontext *lsmcxt);
 int security_dentry_create_files_as(struct dentry *dentry, int mode,
 					struct qstr *name,
 					const struct cred *old,
@@ -855,8 +855,7 @@ static inline int security_dentry_init_security(struct dentry *dentry,
 						 int mode,
 						 const struct qstr *name,
 						 const char **xattr_name,
-						 void **ctx,
-						 u32 *ctxlen)
+						 struct lsmcontext *lsmcxt)
 {
 	return -EOPNOTSUPP;
 }
diff --git a/security/security.c b/security/security.c
index e1487979603e..cea3c1b614a1 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1666,8 +1666,7 @@ void security_inode_free(struct inode *inode)
  * @mode: mode used to determine resource type
  * @name: name of the last path component
  * @xattr_name: name of the security/LSM xattr
- * @ctx: pointer to the resulting LSM context
- * @ctxlen: length of @ctx
+ * @lsmctx: pointer to the resulting LSM context
  *
  * Compute a context for a dentry as the inode is not yet available since NFSv4
  * has no label backed by an EA anyway.  It is important to note that
@@ -1677,8 +1676,8 @@ void security_inode_free(struct inode *inode)
  */
 int security_dentry_init_security(struct dentry *dentry, int mode,
 				  const struct qstr *name,
-				  const char **xattr_name, void **ctx,
-				  u32 *ctxlen)
+				  const char **xattr_name,
+				  struct lsmcontext *lsmctx)
 {
 	struct security_hook_list *hp;
 	int rc;
@@ -1689,7 +1688,7 @@ int security_dentry_init_security(struct dentry *dentry, int mode,
 	hlist_for_each_entry(hp, &security_hook_heads.dentry_init_security,
 			     list) {
 		rc = hp->hook.dentry_init_security(dentry, mode, name,
-						   xattr_name, ctx, ctxlen);
+						   xattr_name, lsmctx);
 		if (rc != LSM_RET_DEFAULT(dentry_init_security))
 			return rc;
 	}
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 1e97b703f252..ed4237223959 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2859,8 +2859,8 @@ static void selinux_inode_free_security(struct inode *inode)
 
 static int selinux_dentry_init_security(struct dentry *dentry, int mode,
 					const struct qstr *name,
-					const char **xattr_name, void **ctx,
-					u32 *ctxlen)
+					const char **xattr_name,
+					struct lsmcontext *cp)
 {
 	u32 newsid;
 	int rc;
@@ -2875,8 +2875,9 @@ static int selinux_dentry_init_security(struct dentry *dentry, int mode,
 	if (xattr_name)
 		*xattr_name = XATTR_NAME_SELINUX;
 
-	return security_sid_to_context(newsid, (char **)ctx,
-				       ctxlen);
+	cp->id = LSM_ID_SELINUX;
+	return security_sid_to_context(newsid, (char **)cp->context,
+				       &cp->len);
 }
 
 static int selinux_dentry_create_files_as(struct dentry *dentry, int mode,
-- 
2.41.0