6 files changed, 85 insertions, 0 deletions

diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
index d1b4a119d4a5..028b78168d85 100644
--- a/arch/x86/syscalls/syscall_32.tbl
+++ b/arch/x86/syscalls/syscall_32.tbl
@@ -362,3 +362,4 @@
 353     i386    renameat2               sys_renameat2
 354     i386    seccomp                 sys_seccomp
 355     i386    getrandom               sys_getrandom
+356     i386    memfd_create            sys_memfd_create
diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
index 252c804bb1aa..ca2b9aa78c81 100644
--- a/arch/x86/syscalls/syscall_64.tbl
+++ b/arch/x86/syscalls/syscall_64.tbl
@@ -325,6 +325,7 @@
 316     common  renameat2               sys_renameat2
 317     common  seccomp                 sys_seccomp
 318     common  getrandom               sys_getrandom
+319     common  memfd_create            sys_memfd_create
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 701daff5d899..15a069425cbf 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -802,6 +802,7 @@ asmlinkage long sys_timerfd_settime(int ufd, int flags,
 asmlinkage long sys_timerfd_gettime(int ufd, struct itimerspec __user *otmr);
 asmlinkage long sys_eventfd(unsigned int count);
 asmlinkage long sys_eventfd2(unsigned int count, int flags);
+asmlinkage long sys_memfd_create(const char __user *uname_ptr, unsigned int flags);
 asmlinkage long sys_fallocate(int fd, int mode, loff_t offset, loff_t len);
 asmlinkage long sys_old_readdir(unsigned int, struct old_linux_dirent __user *, unsigned int);
 asmlinkage long sys_pselect6(int, fd_set __user *, fd_set __user *,
diff --git a/include/uapi/linux/memfd.h b/include/uapi/linux/memfd.h
new file mode 100644
index 000000000000..534e364bda92
--- /dev/null
+++ b/include/uapi/linux/memfd.h
@@ -0,0 +1,8 @@
+#ifndef _UAPI_LINUX_MEMFD_H
+#define _UAPI_LINUX_MEMFD_H
+
+/* flags for memfd_create(2) (unsigned int) */
+#define MFD_CLOEXEC             0x0001U
+#define MFD_ALLOW_SEALING       0x0002U
+
+#endif /* _UAPI_LINUX_MEMFD_H */
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 2904a2105914..1f79e3714533 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -197,6 +197,7 @@ cond_syscall(compat_sys_timerfd_settime);
 cond_syscall(compat_sys_timerfd_gettime);
 cond_syscall(sys_eventfd);
 cond_syscall(sys_eventfd2);
+cond_syscall(sys_memfd_create);
 
 /* performance counters: */
 cond_syscall(sys_perf_event_open);
diff --git a/mm/shmem.c b/mm/shmem.c
index 8b43bb7a4efe..4a5498795a2b 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -66,7 +66,9 @@ static struct vfsmount *shm_mnt;
 #include <linux/highmem.h>
 #include <linux/seq_file.h>
 #include <linux/magic.h>
+#include <linux/syscalls.h>
 #include <linux/fcntl.h>
+#include <uapi/linux/memfd.h>
 
 #include <asm/uaccess.h>
 #include <asm/pgtable.h>
@@ -2732,6 +2734,77 @@ static int shmem_show_options(struct seq_file *seq, struct dentry *root)
         shmem_show_mpol(seq, sbinfo->mpol);
         return 0;
 }
+
+#define MFD_NAME_PREFIX "memfd:"
+#define MFD_NAME_PREFIX_LEN (sizeof(MFD_NAME_PREFIX) - 1)
+#define MFD_NAME_MAX_LEN (NAME_MAX - MFD_NAME_PREFIX_LEN)
+
+#define MFD_ALL_FLAGS (MFD_CLOEXEC | MFD_ALLOW_SEALING)
+
+SYSCALL_DEFINE2(memfd_create,
+                const char __user *, uname,
+                unsigned int, flags)
+{
+        struct shmem_inode_info *info;
+        struct file *file;
+        int fd, error;
+        char *name;
+        long len;
+
+        if (flags & ~(unsigned int)MFD_ALL_FLAGS)
+                return -EINVAL;
+
+        /* length includes terminating zero */
+        len = strnlen_user(uname, MFD_NAME_MAX_LEN + 1);
+        if (len <= 0)
+                return -EFAULT;
+        if (len > MFD_NAME_MAX_LEN + 1)
+                return -EINVAL;
+
+        name = kmalloc(len + MFD_NAME_PREFIX_LEN, GFP_TEMPORARY);
+        if (!name)
+                return -ENOMEM;
+
+        strcpy(name, MFD_NAME_PREFIX);
+        if (copy_from_user(&name[MFD_NAME_PREFIX_LEN], uname, len)) {
+                error = -EFAULT;
+                goto err_name;
+        }
+
+        /* terminating-zero may have changed after strnlen_user() returned */
+        if (name[len + MFD_NAME_PREFIX_LEN - 1]) {
+                error = -EFAULT;
+                goto err_name;
+        }
+
+        fd = get_unused_fd_flags((flags & MFD_CLOEXEC) ? O_CLOEXEC : 0);
+        if (fd < 0) {
+                error = fd;
+                goto err_name;
+        }
+
+        file = shmem_file_setup(name, 0, VM_NORESERVE);
+        if (IS_ERR(file)) {
+                error = PTR_ERR(file);
+                goto err_fd;
+        }
+        info = SHMEM_I(file_inode(file));
+        file->f_mode |= FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE;
+        file->f_flags |= O_RDWR | O_LARGEFILE;
+        if (flags & MFD_ALLOW_SEALING)
+                info->seals &= ~F_SEAL_SEAL;
+
+        fd_install(fd, file);
+        kfree(name);
+        return fd;
+
+err_fd:
+        put_unused_fd(fd);
+err_name:
+        kfree(name);
+        return error;
+}
+
 #endif /* CONFIG_TMPFS */
 
 static void shmem_put_super(struct super_block *sb)