[PATCH v3 0/1] fuse: Send file/inode security context during creation

@@ -17,6 +17,9 @@
 #include <linux/xattr.h>
 #include <linux/iversion.h>
 #include <linux/posix_acl.h>
+#include <linux/security.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
 
 static void fuse_advise_use_readdirplus(struct inode *dir)
 {

@@ -456,6 +459,69 @@ static struct dentry *fuse_lookup(struct inode *dir, struct dentry *entry,
 	return ERR_PTR(err);
 }
 
+static int get_security_context(struct dentry *entry, umode_t mode,
+				void **security_ctx, u32 *security_ctxlen)
+{
+	struct fuse_secctx *fsecctx;
+	struct fuse_secctx_header *fsecctx_header;
+	void *ctx, *full_ctx;
+	u32 ctxlen, full_ctxlen;
+	int err = 0;
+	const char *name;
+
+	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 */
+		err = 0;
+		ctxlen = 0;
+	}
+
+	if (ctxlen > 0) {
+		void *ptr;
+
+		full_ctxlen = sizeof(*fsecctx_header) + sizeof(*fsecctx) +
+			      strlen(name) + ctxlen + 1;
+		full_ctx = kzalloc(full_ctxlen, GFP_KERNEL);
+		if (!full_ctx) {
+			err = -ENOMEM;
+			kfree(ctx);
+			goto out_err;
+		}
+
+		ptr = full_ctx;
+		fsecctx_header = (struct fuse_secctx_header*) ptr;
+		fsecctx_header->nr_secctx = 1;
+		fsecctx_header->size = full_ctxlen;
+		ptr += sizeof(*fsecctx_header);
+
+		fsecctx = (struct fuse_secctx*) ptr;
+		fsecctx->size = ctxlen;
+		ptr += sizeof(*fsecctx);
+
+		strcpy(ptr, name);
+		ptr += strlen(name) + 1;
+		memcpy(ptr, ctx, ctxlen);
+		kfree(ctx);
+	} else {
+		full_ctxlen = sizeof(*fsecctx_header);
+		full_ctx = kzalloc(full_ctxlen, GFP_KERNEL);
+		if (!full_ctx) {
+			err = -ENOMEM;
+			goto out_err;
+		}
+		fsecctx_header = full_ctx;
+		fsecctx_header->size = full_ctxlen;
+	}
+
+	*security_ctxlen = full_ctxlen;
+	*security_ctx = full_ctx;
+out_err:
+	return err;
+}
+
 /*
  * Atomic create+open operation
  *

@@ -476,6 +542,8 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
 	struct fuse_entry_out outentry;
 	struct fuse_inode *fi;
 	struct fuse_file *ff;
+	void *security_ctx = NULL;
+	u32 security_ctxlen;
 
 	/* Userspace expects S_IFREG in create mode */
 	BUG_ON((mode & S_IFMT) != S_IFREG);

@@ -517,6 +585,18 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
 	args.out_args[0].value = &outentry;
 	args.out_args[1].size = sizeof(outopen);
 	args.out_args[1].value = &outopen;
+
+	if (fm->fc->init_security) {
+		err = get_security_context(entry, mode, &security_ctx,
+					   &security_ctxlen);
+		if (err)
+			goto out_put_forget_req;
+
+		args.in_numargs = 3;
+		args.in_args[2].size = security_ctxlen;
+		args.in_args[2].value = security_ctx;
+	}
+
 	err = fuse_simple_request(fm, &args);
 	if (err)
 		goto out_free_ff;

@@ -554,6 +634,7 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry,
 
 out_free_ff:
 	fuse_file_free(ff);
+	kfree(security_ctx);
 out_put_forget_req:
 	kfree(forget);
 out_err:

@@ -620,6 +701,8 @@ static int create_new_entry(struct fuse_mount *fm, struct fuse_args *args,
 	struct dentry *d;
 	int err;
 	struct fuse_forget_link *forget;
+	void *security_ctx = NULL;
+	u32 security_ctxlen = 0;
 
 	if (fuse_is_bad(dir))
 		return -EIO;

@@ -633,7 +716,27 @@ static int create_new_entry(struct fuse_mount *fm, struct fuse_args *args,
 	args->out_numargs = 1;
 	args->out_args[0].size = sizeof(outarg);
 	args->out_args[0].value = &outarg;
+
+	if (fm->fc->init_security && args->opcode != FUSE_LINK) {
+		unsigned short idx = args->in_numargs;
+
+		if ((size_t)idx >= ARRAY_SIZE(args->in_args)) {
+			err = -ENOMEM;
+			goto out_put_forget_req;
+		}
+
+		err = get_security_context(entry, mode, &security_ctx,
+					   &security_ctxlen);
+		if (err)
+			goto out_put_forget_req;
+
+		args->in_args[idx].size = security_ctxlen;
+		args->in_args[idx].value = security_ctx;
+		args->in_numargs++;
+	}
+
 	err = fuse_simple_request(fm, args);
+	kfree(security_ctx);
 	if (err)
 		goto out_put_forget_req;
 

@@ -765,6 +765,9 @@ struct fuse_conn {
 	/* Propagate syncfs() to server */
 	unsigned int sync_fs:1;
 
+	/* Initialize security xattrs when creating a new inode */
+	unsigned int init_security:1;
+
 	/** The number of requests waiting for completion */
 	atomic_t num_waiting;
 

@@ -1143,6 +1143,8 @@ static void process_init_reply(struct fuse_mount *fm, struct fuse_args *args,
 			}
 			if (arg->flags & FUSE_SETXATTR_EXT)
 				fc->setxattr_ext = 1;
+			if (arg->flags & FUSE_SECURITY_CTX)
+				fc->init_security = 1;
 		} else {
 			ra_pages = fc->max_read / PAGE_SIZE;
 			fc->no_lock = 1;

@@ -1186,7 +1188,7 @@ void fuse_send_init(struct fuse_mount *fm)
 		FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL |
 		FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |
 		FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA |
-		FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT;
+		FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT | FUSE_SECURITY_CTX;
 #ifdef CONFIG_FUSE_DAX
 	if (fm->fc->dax)
 		ia->in.flags |= FUSE_MAP_ALIGNMENT;

@@ -184,6 +184,10 @@
  *
  *  7.34
  *  - add FUSE_SYNCFS
+ *
+ *  7.35
+ *  - add FUSE_SECURITY_CTX flag for fuse_init_out
+ *  - add security context to create, mkdir, symlink, and mknod requests
  */
 
 #ifndef _LINUX_FUSE_H

@@ -219,7 +223,7 @@
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 34
+#define FUSE_KERNEL_MINOR_VERSION 35
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1

@@ -336,6 +340,8 @@ struct fuse_file_lock {
  *			write/truncate sgid is killed only if file has group
  *			execute permission. (Same as Linux VFS behavior).
  * FUSE_SETXATTR_EXT:	Server supports extended struct fuse_setxattr_in
+ * FUSE_SECURITY_CTX:	add security context to create, mkdir, symlink, and
+ * 			mknod
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)

@@ -367,6 +373,7 @@ struct fuse_file_lock {
 #define FUSE_SUBMOUNTS		(1 << 27)
 #define FUSE_HANDLE_KILLPRIV_V2	(1 << 28)
 #define FUSE_SETXATTR_EXT	(1 << 29)
+#define FUSE_SECURITY_CTX	(1 << 30)
 
 /**
  * CUSE INIT request/reply flags

@@ -979,4 +986,26 @@ struct fuse_syncfs_in {
 	uint64_t	padding;
 };
 
+/*
+ * For each security context, send fuse_secctx with size of security context
+ * fuse_secctx will be followed by security context name and this in turn
+ * will be followed by actual context label.
+ * fuse_secctx, name, context
+ * */
+struct fuse_secctx {
+	uint32_t	size;
+	uint32_t	padding;
+};
+
+/*
+ * Contains the information about how many fuse_secctx structures are being
+ * sent and what's the total size of all security contexts (including
+ * size of fuse_secctx_header).
+ *
+ */
+struct fuse_secctx_header {
+	uint32_t	size;
+	uint32_t	nr_secctx;
+};
+
 #endif /* _LINUX_FUSE_H */

@@ -187,6 +187,10 @@
  *
  *  7.35
  *  - add FOPEN_NOFLUSH
+ *
+ *  7.36
+ *  - add FUSE_SECURITY_CTX flag for fuse_init_out
+ *  - add security context to create, mkdir, symlink, and mknod requests
  */
 
 #ifndef _LINUX_FUSE_H

@@ -222,7 +226,7 @@
 #define FUSE_KERNEL_VERSION 7
 
 /** Minor version number of this interface */
-#define FUSE_KERNEL_MINOR_VERSION 35
+#define FUSE_KERNEL_MINOR_VERSION 36
 
 /** The node ID of the root inode */
 #define FUSE_ROOT_ID 1

@@ -341,6 +345,8 @@ struct fuse_file_lock {
  *			write/truncate sgid is killed only if file has group
  *			execute permission. (Same as Linux VFS behavior).
  * FUSE_SETXATTR_EXT:	Server supports extended struct fuse_setxattr_in
+ * FUSE_SECURITY_CTX:	add security context to create, mkdir, symlink, and
+ * 			mknod
  */
 #define FUSE_ASYNC_READ		(1 << 0)
 #define FUSE_POSIX_LOCKS	(1 << 1)

@@ -372,6 +378,7 @@ struct fuse_file_lock {
 #define FUSE_SUBMOUNTS		(1 << 27)
 #define FUSE_HANDLE_KILLPRIV_V2	(1 << 28)
 #define FUSE_SETXATTR_EXT	(1 << 29)
+#define FUSE_SECURITY_CTX	(1 << 30)
 
 /**
  * CUSE INIT request/reply flags

@@ -984,4 +991,26 @@ struct fuse_syncfs_in {
 	uint64_t	padding;
 };
 
+/*
+ * For each security context, send fuse_secctx with size of security context
+ * fuse_secctx will be followed by security context name and this in turn
+ * will be followed by actual context label.
+ * fuse_secctx, name, context
+ * */
+struct fuse_secctx {
+	uint32_t	size;
+	uint32_t	padding;
+};
+
+/*
+ * Contains the information about how many fuse_secctx structures are being
+ * sent and what's the total size of all security contexts (including
+ * size of fuse_secctx_header).
+ *
+ */
+struct fuse_secctx_header {
+	uint32_t	size;
+	uint32_t	nr_secctx;
+};
+
 #endif /* _LINUX_FUSE_H */

@@ -17,6 +17,9 @@
 #include <linux/xattr.h>
 #include <linux/iversion.h>
 #include <linux/posix_acl.h>
+#include <linux/security.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
 
 static void fuse_advise_use_readdirplus(struct inode *dir)
 {

@@ -456,6 +459,69 @@ static struct dentry *fuse_lookup(struct
 	return ERR_PTR(err);
 }
 
+static int get_security_context(struct dentry *entry, umode_t mode,
+				void **security_ctx, u32 *security_ctxlen)
+{
+	struct fuse_secctx *fsecctx;
+	struct fuse_secctx_header *fsecctx_header;
+	void *ctx, *full_ctx;
+	u32 ctxlen, full_ctxlen;
+	int err = 0;
+	const char *name;
+
+	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 */
+		err = 0;
+		ctxlen = 0;
+	}
+
+	if (ctxlen > 0) {
+		void *ptr;
+
+		full_ctxlen = sizeof(*fsecctx_header) + sizeof(*fsecctx) +
+			      strlen(name) + ctxlen + 1;
+		full_ctx = kzalloc(full_ctxlen, GFP_KERNEL);
+		if (!full_ctx) {
+			err = -ENOMEM;
+			kfree(ctx);
+			goto out_err;
+		}
+
+		ptr = full_ctx;
+		fsecctx_header = (struct fuse_secctx_header*) ptr;
+		fsecctx_header->nr_secctx = 1;
+		fsecctx_header->size = full_ctxlen;
+		ptr += sizeof(*fsecctx_header);
+
+		fsecctx = (struct fuse_secctx*) ptr;
+		fsecctx->size = ctxlen;
+		ptr += sizeof(*fsecctx);
+
+		strcpy(ptr, name);
+		ptr += strlen(name) + 1;
+		memcpy(ptr, ctx, ctxlen);
+		kfree(ctx);
+	} else {
+		full_ctxlen = sizeof(*fsecctx_header);
+		full_ctx = kzalloc(full_ctxlen, GFP_KERNEL);
+		if (!full_ctx) {
+			err = -ENOMEM;
+			goto out_err;
+		}
+		fsecctx_header = full_ctx;
+		fsecctx_header->size = full_ctxlen;
+	}
+
+	*security_ctxlen = full_ctxlen;
+	*security_ctx = full_ctx;
+out_err:
+	return err;
+}
+
 /*
  * Atomic create+open operation
  *

@@ -476,6 +542,8 @@ static int fuse_create_open(struct inode
 	struct fuse_entry_out outentry;
 	struct fuse_inode *fi;
 	struct fuse_file *ff;
+	void *security_ctx = NULL;
+	u32 security_ctxlen;
 
 	/* Userspace expects S_IFREG in create mode */
 	BUG_ON((mode & S_IFMT) != S_IFREG);

@@ -517,6 +585,18 @@ static int fuse_create_open(struct inode
 	args.out_args[0].value = &outentry;
 	args.out_args[1].size = sizeof(outopen);
 	args.out_args[1].value = &outopen;
+
+	if (fm->fc->init_security) {
+		err = get_security_context(entry, mode, &security_ctx,
+					   &security_ctxlen);
+		if (err)
+			goto out_put_forget_req;
+
+		args.in_numargs = 3;
+		args.in_args[2].size = security_ctxlen;
+		args.in_args[2].value = security_ctx;
+	}
+
 	err = fuse_simple_request(fm, &args);
 	if (err)
 		goto out_free_ff;

@@ -554,6 +634,7 @@ static int fuse_create_open(struct inode
 
 out_free_ff:
 	fuse_file_free(ff);
+	kfree(security_ctx);
 out_put_forget_req:
 	kfree(forget);
 out_err:

@@ -620,6 +701,8 @@ static int create_new_entry(struct fuse_
 	struct dentry *d;
 	int err;
 	struct fuse_forget_link *forget;
+	void *security_ctx = NULL;
+	u32 security_ctxlen = 0;
 
 	if (fuse_is_bad(dir))
 		return -EIO;

@@ -633,7 +716,27 @@ static int create_new_entry(struct fuse_
 	args->out_numargs = 1;
 	args->out_args[0].size = sizeof(outarg);
 	args->out_args[0].value = &outarg;
+
+	if (fm->fc->init_security && args->opcode != FUSE_LINK) {
+		unsigned short idx = args->in_numargs;
+
+		if ((size_t)idx >= ARRAY_SIZE(args->in_args)) {
+			err = -ENOMEM;
+			goto out_put_forget_req;
+		}
+
+		err = get_security_context(entry, mode, &security_ctx,
+					   &security_ctxlen);
+		if (err)
+			goto out_put_forget_req;
+
+		args->in_args[idx].size = security_ctxlen;
+		args->in_args[idx].value = security_ctx;
+		args->in_numargs++;
+	}
+
 	err = fuse_simple_request(fm, args);
+	kfree(security_ctx);
 	if (err)
 		goto out_put_forget_req;
 

@@ -765,6 +765,9 @@ struct fuse_conn {
 	/* Propagate syncfs() to server */
 	unsigned int sync_fs:1;
 
+	/* Initialize security xattrs when creating a new inode */
+	unsigned int init_security:1;
+
 	/** The number of requests waiting for completion */
 	atomic_t num_waiting;
 

@@ -1176,6 +1176,8 @@ static void process_init_reply(struct fu
 			}
 			if (arg->flags & FUSE_SETXATTR_EXT)
 				fc->setxattr_ext = 1;
+			if (arg->flags & FUSE_SECURITY_CTX)
+				fc->init_security = 1;
 		} else {
 			ra_pages = fc->max_read / PAGE_SIZE;
 			fc->no_lock = 1;

@@ -1219,7 +1221,7 @@ void fuse_send_init(struct fuse_mount *f
 		FUSE_PARALLEL_DIROPS | FUSE_HANDLE_KILLPRIV | FUSE_POSIX_ACL |
 		FUSE_ABORT_ERROR | FUSE_MAX_PAGES | FUSE_CACHE_SYMLINKS |
 		FUSE_NO_OPENDIR_SUPPORT | FUSE_EXPLICIT_INVAL_DATA |
-		FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT;
+		FUSE_HANDLE_KILLPRIV_V2 | FUSE_SETXATTR_EXT | FUSE_SECURITY_CTX;
 #ifdef CONFIG_FUSE_DAX
 	if (fm->fc->dax)
 		ia->in.flags |= FUSE_MAP_ALIGNMENT;