2  * memfd_create system call and file sealing support
7  * This file is released under the GPL.
13 #include <linux/file.h>
68 struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx)  in memfd_alloc_folio()
173 static unsigned int *memfd_file_seals_ptr(struct file *file)  in memfd_file_seals_ptr()  argument
175 	if (shmem_file(file))  in memfd_file_seals_ptr()
176 		return &SHMEM_I(file_inode(file))->seals;  in memfd_file_seals_ptr()
179 	if (is_file_hugepages(file))  in memfd_file_seals_ptr()
180 		return &HUGETLBFS_I(file_inode(file))->seals;  in memfd_file_seals_ptr()
193 static int memfd_add_seals(struct file *file, unsigned int seals)  in memfd_add_seals()  argument
195 	struct inode *inode = file_inode(file);  in memfd_add_seals()
201 	 * Sealing allows multiple parties to share a tmpfs or hugetlbfs file  in memfd_add_seals()
202 	 * but restrict access to a specific subset of file operations. Seals  in memfd_add_seals()
210 	 * may prevent some kinds of access to the file. Currently, the  in memfd_add_seals()
212 	 *   SEAL_SEAL: Prevent further seals from being set on this file  in memfd_add_seals()
213 	 *   SEAL_SHRINK: Prevent the file from shrinking  in memfd_add_seals()
214 	 *   SEAL_GROW: Prevent the file from growing  in memfd_add_seals()
215 	 *   SEAL_WRITE: Prevent write access to the file  in memfd_add_seals()
216 	 *   SEAL_EXEC: Prevent modification of the exec bits in the file mode  in memfd_add_seals()
219 	 * must prevent seals from being removed. Therefore, sealing a file  in memfd_add_seals()
220 	 * only adds a given set of seals to the file, it never touches  in memfd_add_seals()
228 	 * no plan to support it on other file types.  in memfd_add_seals()
231 	if (!(file->f_mode & FMODE_WRITE))  in memfd_add_seals()
238 	file_seals = memfd_file_seals_ptr(file);  in memfd_add_seals()
250 		error = mapping_deny_writable(file->f_mapping);  in memfd_add_seals()
254 		error = memfd_wait_for_pins(file->f_mapping);  in memfd_add_seals()
256 			mapping_allow_writable(file->f_mapping);  in memfd_add_seals()
275 static int memfd_get_seals(struct file *file)  in memfd_get_seals()  argument
277 	unsigned int *seals = memfd_file_seals_ptr(file);  in memfd_get_seals()
282 long memfd_fcntl(struct file *file, unsigned int cmd, unsigned int arg)  in memfd_fcntl()  argument
288 		error = memfd_add_seals(file, arg);  in memfd_fcntl()
291 		error = memfd_get_seals(file);  in memfd_fcntl()
360 int memfd_check_seals_mmap(struct file *file, unsigned long *vm_flags_ptr)  in memfd_check_seals_mmap()  argument
363 	unsigned int *seals_ptr = memfd_file_seals_ptr(file);  in memfd_check_seals_mmap()
421 static struct file *alloc_file(const char *name, unsigned int flags)  in alloc_file()
424 	struct file *file;  in alloc_file()  local
427 		file = hugetlb_file_setup(name, 0, VM_NORESERVE,  in alloc_file()
432 		file = shmem_file_setup(name, 0, VM_NORESERVE);  in alloc_file()
434 	if (IS_ERR(file))  in alloc_file()
435 		return file;  in alloc_file()
436 	file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;  in alloc_file()
437 	file->f_flags |= O_LARGEFILE;  in alloc_file()
440 		struct inode *inode = file_inode(file);  in alloc_file()
443 		file_seals = memfd_file_seals_ptr(file);  in alloc_file()
450 		file_seals = memfd_file_seals_ptr(file);  in alloc_file()
455 	return file;  in alloc_file()
462 	struct file *file;  in SYSCALL_DEFINE2()  local
480 	file = alloc_file(name, flags);  in SYSCALL_DEFINE2()
481 	if (IS_ERR(file)) {  in SYSCALL_DEFINE2()
482 		error = PTR_ERR(file);  in SYSCALL_DEFINE2()
486 	fd_install(fd, file);  in SYSCALL_DEFINE2()