Merge tag 'vfs-6.18-rc1.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Pull vfs mount updates from Christian Brauner:
 "This contains some work around mount api handling:

   - Output the warning message for mnt_too_revealing() triggered during
     fsmount() to the fscontext log. This makes it possible for the
     mount tool to output appropriate warnings on the command line.

     For example, with the newest fsopen()-based mount(8) from
     util-linux, the error messages now look like:

       # mount -t proc proc /tmp
       mount: /tmp: fsmount() failed: VFS: Mount too revealing.
              dmesg(1) may have more information after failed mount system call.

   - Do not consume fscontext log entries when returning -EMSGSIZE

     Userspace generally expects APIs that return -EMSGSIZE to allow for
     them to adjust their buffer size and retry the operation.

     However, the fscontext log would previously clear the message even
     in the -EMSGSIZE case.

     Given that it is very cheap for us to check whether the buffer is
     too small before we remove the message from the ring buffer, let's
     just do that instead.

   - Drop an unused argument from do_remount()"

* tag 'vfs-6.18-rc1.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs:
  vfs: fs/namespace.c: remove ms_flags argument from do_remount
  selftests/filesystems: add basic fscontext log tests
  fscontext: do not consume log entries when returning -EMSGSIZE
  vfs: output mount_too_revealing() errors to fscontext
  docs/vfs: Remove mentions to the old mount API helpers
  fscontext: add custom-prefix log helpers
  fs: Remove mount_bdev
  fs: Remove mount_nodev

1 files changed, 6 insertions, 4 deletions

diff --git a/fs/namespace.c b/fs/namespace.c
index 1ee17a00c311..d0be7401b0b5 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3298,7 +3298,7 @@ static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags)
  * If you've mounted a non-root directory somewhere and want to do remount
  * on it - tough luck.
  */
-static int do_remount(struct path *path, int ms_flags, int sb_flags,
+static int do_remount(struct path *path, int sb_flags,
 		      int mnt_flags, void *data)
 {
 	int err;
@@ -3736,8 +3736,10 @@ static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint,
 	int error;
 
 	error = security_sb_kern_mount(sb);
-	if (!error && mount_too_revealing(sb, &mnt_flags))
+	if (!error && mount_too_revealing(sb, &mnt_flags)) {
+		errorfcp(fc, "VFS", "Mount too revealing");
 		error = -EPERM;
+	}
 
 	if (unlikely(error)) {
 		fc_drop_locked(fc);
@@ -4121,7 +4123,7 @@ int path_mount(const char *dev_name, struct path *path,
 	if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND))
 		return do_reconfigure_mnt(path, mnt_flags);
 	if (flags & MS_REMOUNT)
-		return do_remount(path, flags, sb_flags, mnt_flags, data_page);
+		return do_remount(path, sb_flags, mnt_flags, data_page);
 	if (flags & MS_BIND)
 		return do_loopback(path, dev_name, flags & MS_REC);
 	if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
@@ -4453,7 +4455,7 @@ SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags,
 
 	ret = -EPERM;
 	if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) {
-		pr_warn("VFS: Mount too revealing\n");
+		errorfcp(fc, "VFS", "Mount too revealing");
 		goto err_unlock;
 	}