From: Eric Biggers ebiggers@google.com Subject: fs/filesystems.c: downgrade user-reachable WARN_ONCE() to pr_warn_once()

After request_module(), nothing is stopping the module from being unloaded until someone takes a reference to it via try_get_module().

The WARN_ONCE() in get_fs_type() is thus user-reachable, via userspace running 'rmmod' concurrently.

Since WARN_ONCE() is for kernel bugs only, not for user-reachable situations, downgrade this warning to pr_warn_once().

Keep it printed once only, since the intent of this warning is to detect a bug in modprobe at boot time. Printing the warning more than once wouldn't really provide any useful extra information.

Link: http://lkml.kernel.org/r/20200312202552.241885-3-ebiggers@kernel.org Fixes: 41124db869b7 ("fs: warn in case userspace lied about modprobe return") Signed-off-by: Eric Biggers ebiggers@google.com Reviewed-by: Jessica Yu jeyu@kernel.org Cc: Alexei Starovoitov ast@kernel.org Cc: Greg Kroah-Hartman gregkh@linuxfoundation.org Cc: Jeff Vander Stoep jeffv@google.com Cc: Jessica Yu jeyu@kernel.org Cc: Kees Cook keescook@chromium.org Cc: Luis Chamberlain mcgrof@kernel.org Cc: NeilBrown neilb@suse.com Cc: stable@vger.kernel.org [4.13+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

fs/filesystems.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/fs/filesystems.c~fs-filesystemsc-downgrade-user-reachable-warn_once-to-pr_warn_once +++ a/fs/filesystems.c @@ -272,7 +272,9 @@ struct file_system_type *get_fs_type(con fs = __get_fs_type(name, len); if (!fs && (request_module("fs-%.*s", len, name) == 0)) { fs = __get_fs_type(name, len); - WARN_ONCE(!fs, "request_module fs-%.*s succeeded, but still no fs?\n", len, name); + if (!fs) + pr_warn_once("request_module fs-%.*s succeeded, but still no fs?\n", + len, name); }

if (dot && fs && !(fs->fs_flags & FS_HAS_SUBTYPE)) { _