5 files changed, 68 insertions, 1 deletions

diff --git a/arch/x86/entry/syscalls/syscall_32.tbl b/arch/x86/entry/syscalls/syscall_32.tbl
index 5b5c9189c507..4cd5f982b1e5 100644
--- a/arch/x86/entry/syscalls/syscall_32.tbl
+++ b/arch/x86/entry/syscalls/syscall_32.tbl
@@ -403,7 +403,7 @@
 389     i386    fsopen                  sys_fsopen                      __ia32_sys_fsopen
 390     i386    fsconfig                sys_fsconfig                    __ia32_sys_fsconfig
 391     i386    fsmount                 sys_fsmount                     __ia32_sys_fsmount
-# don't use number 392, add new calls at the end
+392     i386    fspick                  sys_fspick                      __ia32_sys_fspick
 393     i386    semget                  sys_semget                      __ia32_sys_semget
 394     i386    semctl                  sys_semctl                      __ia32_compat_sys_semctl
 395     i386    shmget                  sys_shmget                      __ia32_sys_shmget
diff --git a/arch/x86/entry/syscalls/syscall_64.tbl b/arch/x86/entry/syscalls/syscall_64.tbl
index 984ad594bb2b..64ca0d06259a 100644
--- a/arch/x86/entry/syscalls/syscall_64.tbl
+++ b/arch/x86/entry/syscalls/syscall_64.tbl
@@ -348,6 +348,7 @@
 337     common  fsopen                  __x64_sys_fsopen
 338     common  fsconfig                __x64_sys_fsconfig
 339     common  fsmount                 __x64_sys_fsmount
+340     common  fspick                  __x64_sys_fspick
 # don't use numbers 387 through 423, add new calls after the last
 # 'common' entry
 424     common  pidfd_send_signal       __x64_sys_pidfd_send_signal
diff --git a/fs/fsopen.c b/fs/fsopen.c
index 65cc2f68f994..3bb9c0c8cbcc 100644
--- a/fs/fsopen.c
+++ b/fs/fsopen.c
@@ -157,6 +157,63 @@ err_fc:
 }
 
 /*
+ * Pick a superblock into a context for reconfiguration.
+ */
+SYSCALL_DEFINE3(fspick, int, dfd, const char __user *, path, unsigned int, flags)
+{
+        struct fs_context *fc;
+        struct path target;
+        unsigned int lookup_flags;
+        int ret;
+
+        if (!ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN))
+                return -EPERM;
+
+        if ((flags & ~(FSPICK_CLOEXEC |
+                       FSPICK_SYMLINK_NOFOLLOW |
+                       FSPICK_NO_AUTOMOUNT |
+                       FSPICK_EMPTY_PATH)) != 0)
+                return -EINVAL;
+
+        lookup_flags = LOOKUP_FOLLOW | LOOKUP_AUTOMOUNT;
+        if (flags & FSPICK_SYMLINK_NOFOLLOW)
+                lookup_flags &= ~LOOKUP_FOLLOW;
+        if (flags & FSPICK_NO_AUTOMOUNT)
+                lookup_flags &= ~LOOKUP_AUTOMOUNT;
+        if (flags & FSPICK_EMPTY_PATH)
+                lookup_flags |= LOOKUP_EMPTY;
+        ret = user_path_at(dfd, path, lookup_flags, &target);
+        if (ret < 0)
+                goto err;
+
+        ret = -EINVAL;
+        if (target.mnt->mnt_root != target.dentry)
+                goto err_path;
+
+        fc = fs_context_for_reconfigure(target.dentry, 0, 0);
+        if (IS_ERR(fc)) {
+                ret = PTR_ERR(fc);
+                goto err_path;
+        }
+
+        fc->phase = FS_CONTEXT_RECONF_PARAMS;
+
+        ret = fscontext_alloc_log(fc);
+        if (ret < 0)
+                goto err_fc;
+
+        path_put(&target);
+        return fscontext_create_fd(fc, flags & FSPICK_CLOEXEC ? O_CLOEXEC : 0);
+
+err_fc:
+        put_fs_context(fc);
+err_path:
+        path_put(&target);
+err:
+        return ret;
+}
+
+/*
  * Check the state and apply the configuration.  Note that this function is
  * allowed to 'steal' the value by setting param->xxx to NULL before returning.
  */
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 0e697f595278..e2870fe1be5b 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -993,6 +993,7 @@ asmlinkage long sys_fsopen(const char __user *fs_name, unsigned int flags);
 asmlinkage long sys_fsconfig(int fs_fd, unsigned int cmd, const char __user *key,
                              const void __user *value, int aux);
 asmlinkage long sys_fsmount(int fs_fd, unsigned int flags, unsigned int ms_flags);
+asmlinkage long sys_fspick(int dfd, const char __user *path, unsigned int flags);
 asmlinkage long sys_pidfd_send_signal(int pidfd, int sig,
                                        siginfo_t __user *info,
                                        unsigned int flags);
diff --git a/include/uapi/linux/mount.h b/include/uapi/linux/mount.h
index 3888d3b91dc5..96a0240f23fe 100644
--- a/include/uapi/linux/mount.h
+++ b/include/uapi/linux/mount.h
@@ -78,6 +78,14 @@
 #define FSOPEN_CLOEXEC          0x00000001
 
 /*
+ * fspick() flags.
+ */
+#define FSPICK_CLOEXEC          0x00000001
+#define FSPICK_SYMLINK_NOFOLLOW 0x00000002
+#define FSPICK_NO_AUTOMOUNT     0x00000004
+#define FSPICK_EMPTY_PATH       0x00000008
+
+/*
  * The type of fsconfig() call made.
  */
 enum fsconfig_command {