Messages in this thread | | | Date | Wed, 18 Mar 2020 15:54:15 -0700 | From | Eric Biggers <> | Subject | Re: [PATCH v3 2/5] fs/filesystems.c: downgrade user-reachable WARN_ONCE() to pr_warn_once() |
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On Wed, Mar 18, 2020 at 04:43:15PM +0100, Jessica Yu wrote: > +++ Eric Biggers [14/03/20 14:34 -0700]: > > 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(). > > > > Acked-by: Luis Chamberlain <mcgrof@kernel.org> > > 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: 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); > > Hm, what was the rationale for warning only once again? It might be useful > for debugging issues to see each instance of request_module() failure > (and with which fs). However, I don't have a concrete use case to > support this argument, so: > > Reviewed-by: Jessica Yu <jeyu@kernel.org>
This was discussed on v2, see https://lkml.kernel.org/lkml/20200313010053.GS11244@42.do-not-panic.com/. If the warning triggers, then it indicates a broken modprobe program. Printing the warning multiple times wouldn't really add any new information.
And in any case, it's printed once both before and after this patch.
- Eric
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