On Fri, Mar 13, 2020 at 09:06:46AM +1100, NeilBrown wrote:

On Thu, Mar 12 2020, Eric Biggers wrote:

...

From: Eric Biggers ebiggers@google.com

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().

Cc: stable@vger.kernel.org Cc: Alexei Starovoitov ast@kernel.org Cc: Andrew Morton akpm@linux-foundation.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 Signed-off-by: Eric Biggers ebiggers@google.com

---

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

diff --git a/fs/filesystems.c b/fs/filesystems.c index 77bf5f95362da..90b8d879fbaf3 100644 --- a/fs/filesystems.c +++ b/fs/filesystems.c @@ -272,7 +272,9 @@ struct file_system_type *get_fs_type(const char *name) 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);
  

I strongly support the replacement of "WARN" by "pr_warn". I wonder if we really want the "once" now. Possibly using rate_limited would be justified, but I think that in general we should see a warning every time this event happens.

Since the usefulness of the print is at boot, I think pr_warn_once() is good right now but just because I cannot think of a case where multiple prints are currently desirable, or where this should be possible post-boot. Can you?

Luis