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[157.230.128.187]) by smtp.gmail.com with ESMTPSA id g69sm7121370pje.34.2020.03.12.18.00.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Mar 2020 18:00:54 -0700 (PDT) Received: by 42.do-not-panic.com (Postfix, from userid 1000) id E0BD84028E; Fri, 13 Mar 2020 01:00:53 +0000 (UTC) Date: Fri, 13 Mar 2020 01:00:53 +0000 From: Luis Chamberlain To: NeilBrown Cc: Eric Biggers , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Alexei Starovoitov , Andrew Morton , Greg Kroah-Hartman , Jeff Vander Stoep , Jessica Yu , Kees Cook , NeilBrown , stable@vger.kernel.org Subject: Re: [PATCH v2 2/4] fs/filesystems.c: downgrade user-reachable WARN_ONCE() to pr_warn_once() Message-ID: <20200313010053.GS11244@42.do-not-panic.com> References: <20200312202552.241885-1-ebiggers@kernel.org> <20200312202552.241885-3-ebiggers@kernel.org> <87imj9teh5.fsf@notabene.neil.brown.name> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="ADZbWkCsHQ7r3kzd" Content-Disposition: inline In-Reply-To: <87imj9teh5.fsf@notabene.neil.brown.name> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --ADZbWkCsHQ7r3kzd Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Fri, Mar 13, 2020 at 09:06:46AM +1100, NeilBrown wrote: > On Thu, Mar 12 2020, Eric Biggers wrote: >=20 > > From: Eric Biggers > > > > 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 > > Cc: Andrew Morton > > Cc: Greg Kroah-Hartman > > Cc: Jeff Vander Stoep > > Cc: Jessica Yu > > Cc: Kees Cook > > Cc: Luis Chamberlain > > Cc: NeilBrown > > Signed-off-by: Eric Biggers > > --- > > 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 *na= me) > > fs =3D __get_fs_type(name, len); > > if (!fs && (request_module("fs-%.*s", len, name) =3D=3D 0)) { > > fs =3D __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); >=20 > 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? 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