2  * memfd_create system call and file sealing support
7  * This file is released under the GPL.
13 #include <linux/file.h>
136 static unsigned int *memfd_file_seals_ptr(struct file *file)  in memfd_file_seals_ptr()  argument
138 	if (shmem_file(file))  in memfd_file_seals_ptr()
139 		return &SHMEM_I(file_inode(file))->seals;  in memfd_file_seals_ptr()
142 	if (is_file_hugepages(file))  in memfd_file_seals_ptr()
143 		return &HUGETLBFS_I(file_inode(file))->seals;  in memfd_file_seals_ptr()
155 static int memfd_add_seals(struct file *file, unsigned int seals)  in memfd_add_seals()  argument
157 	struct inode *inode = file_inode(file);  in memfd_add_seals()
163 	 * Sealing allows multiple parties to share a tmpfs or hugetlbfs file  in memfd_add_seals()
164 	 * but restrict access to a specific subset of file operations. Seals  in memfd_add_seals()
172 	 * may prevent some kinds of access to the file. Currently, the  in memfd_add_seals()
174 	 *   SEAL_SEAL: Prevent further seals from being set on this file  in memfd_add_seals()
175 	 *   SEAL_SHRINK: Prevent the file from shrinking  in memfd_add_seals()
176 	 *   SEAL_GROW: Prevent the file from growing  in memfd_add_seals()
177 	 *   SEAL_WRITE: Prevent write access to the file  in memfd_add_seals()
180 	 * must prevent seals from being removed. Therefore, sealing a file  in memfd_add_seals()
181 	 * only adds a given set of seals to the file, it never touches  in memfd_add_seals()
189 	 * no plan to support it on other file types.  in memfd_add_seals()
192 	if (!(file->f_mode & FMODE_WRITE))  in memfd_add_seals()
199 	file_seals = memfd_file_seals_ptr(file);  in memfd_add_seals()
211 		error = mapping_deny_writable(file->f_mapping);  in memfd_add_seals()
215 		error = memfd_wait_for_pins(file->f_mapping);  in memfd_add_seals()
217 			mapping_allow_writable(file->f_mapping);  in memfd_add_seals()
230 static int memfd_get_seals(struct file *file)  in memfd_get_seals()  argument
232 	unsigned int *seals = memfd_file_seals_ptr(file);  in memfd_get_seals()
237 long memfd_fcntl(struct file *file, unsigned int cmd, unsigned long arg)  in memfd_fcntl()  argument
247 		error = memfd_add_seals(file, arg);  in memfd_fcntl()
250 		error = memfd_get_seals(file);  in memfd_fcntl()
271 	struct file *file;  in SYSCALL_DEFINE2()  local
316 		file = hugetlb_file_setup(name, 0, VM_NORESERVE,  in SYSCALL_DEFINE2()
321 		file = shmem_file_setup(name, 0, VM_NORESERVE);  in SYSCALL_DEFINE2()
322 	if (IS_ERR(file)) {  in SYSCALL_DEFINE2()
323 		error = PTR_ERR(file);  in SYSCALL_DEFINE2()
326 	file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;  in SYSCALL_DEFINE2()
327 	file->f_flags |= O_LARGEFILE;  in SYSCALL_DEFINE2()
330 		file_seals = memfd_file_seals_ptr(file);  in SYSCALL_DEFINE2()
334 	fd_install(fd, file);  in SYSCALL_DEFINE2()