From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 901191C32; Sun, 26 Jan 2025 12:36:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737894999; cv=none; b=NjU1ar2x1S2nbyFgnAicMgsclOGhgNk7/rJH0mHNvyohvckMuLZMiI5Y5jfVYrOfMAw+veVO0lf7H/uAiL7mlqUWIoUd4RIrha6JpYGfkk4P/l2VITcU8RNd4fw3iSryPfHVads8I6HX9RQ1DqOu7+LchotC+6Ssu/ownYr9Fec= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1737894999; c=relaxed/simple; bh=IHrcIgtuukh/3QTgogEGvP4cxzNTmupmX8ZbDigs34g=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=RdDVqjBBIx3kTnVQx8o2IlZOMa8/mBH4W2imcqgzvt9Ba6XPEx8tWuuyvhu8raUVCP0V7YlwFhGtFPGBqmHPnFue6PR3Q7/F+hz1rvDo7FuPtYsCUcgLpN8jDi4QqTy84XsyvuXdIxJVpbP4hlMrrCYVAwVj3160qGtyfFxj+B8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UN3dAAn5; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UN3dAAn5" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 45AFEC4CED3; Sun, 26 Jan 2025 12:36:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1737894999; bh=IHrcIgtuukh/3QTgogEGvP4cxzNTmupmX8ZbDigs34g=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=UN3dAAn5DIviNSOiQcVQTzAVAKTH3mywKwvI2mUu5SOY3psnmbvyKoFV4q9iw8cxI +mkyiL0LMZEbzyM61WodbbovVT9UuwSkrv0Tgaob1X+lLbiGVmDl3ytkAYDSuriKhu w9zJTsJaPY1A3OjlBJBBQa287tBZSA/TyhNvBD3HpS+LXq0glQCsMqPyMRpE+BaoGz mDjN1HcNw7WqFghLaRk9UPPLvgdlf+PT/hIUEWGUv4cRct6yVt+8abcxDESzEXIhbv mvJTgkokwp4cIeWtl4OlK4hVtk0Y//bUYo6j5lpVK321LdKctgaVIVUWqVRbz/Jzq4 DYVtRvXfErBLg== Message-ID: <02eefb82ddff92f3797c346033300b7d259267d6.camel@kernel.org> Subject: Re: [PATCH] nfsd: validate the nfsd_serv pointer before calling svc_wake_up From: Jeff Layton To: NeilBrown Cc: Chuck Lever , Olga Kornievskaia , Dai Ngo , Tom Talpey , Salvatore Bonaccorso , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org Date: Sun, 26 Jan 2025 07:36:37 -0500 In-Reply-To: <173785917824.22054.15604701394410740651@noble.neil.brown.name> References: <20250125-kdevops-v1-1-a76cf79127b8@kernel.org> <173785917824.22054.15604701394410740651@noble.neil.brown.name> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv 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linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Sun, 2025-01-26 at 13:39 +1100, NeilBrown wrote: > On Sun, 26 Jan 2025, Jeff Layton wrote: > > nfsd_file_dispose_list_delayed can be called from the filecache > > laundrette, which is shut down after the nfsd threads are shut down and > > the nfsd_serv pointer is cleared. If nn->nfsd_serv is NULL then there > > are no threads to wake. > >=20 > > Ensure that the nn->nfsd_serv pointer is non-NULL before calling > > svc_wake_up in nfsd_file_dispose_list_delayed. This is safe since the > > svc_serv is not freed until after the filecache laundrette is cancelled= . > >=20 > > Fixes: ffb402596147 ("nfsd: Don't leave work of closing files to a work= queue") > > Reported-by: Salvatore Bonaccorso > > Closes: https://lore.kernel.org/linux-nfs/7d9f2a8aede4f7ca9935a47e1d405= 643220d7946.camel@kernel.org/ > > Signed-off-by: Jeff Layton > > --- > > This is only lightly tested, but I think it will fix the bug that > > Salvatore reported. > > --- > > fs/nfsd/filecache.c | 11 ++++++++++- > > 1 file changed, 10 insertions(+), 1 deletion(-) > >=20 > > diff --git a/fs/nfsd/filecache.c b/fs/nfsd/filecache.c > > index e91c164b5ea21507659904690533a19ca43b1b64..fb2a4469b7a3c077de2dd75= 0f43239b4af6d37b0 100644 > > --- a/fs/nfsd/filecache.c > > +++ b/fs/nfsd/filecache.c > > @@ -445,11 +445,20 @@ nfsd_file_dispose_list_delayed(struct list_head *= dispose) > > struct nfsd_file, nf_gc); > > struct nfsd_net *nn =3D net_generic(nf->nf_net, nfsd_net_id); > > struct nfsd_fcache_disposal *l =3D nn->fcache_disposal; > > + struct svc_serv *serv; > > =20 > > spin_lock(&l->lock); > > list_move_tail(&nf->nf_gc, &l->freeme); > > spin_unlock(&l->lock); > > - svc_wake_up(nn->nfsd_serv); > > + > > + /* > > + * The filecache laundrette is shut down after the > > + * nn->nfsd_serv pointer is cleared, but before the > > + * svc_serv is freed. > > + */ > > + serv =3D nn->nfsd_serv; >=20 > I wonder if this should be READ_ONCE() to tell the compiler that we > could race with clearing nn->nfsd_serv. Would the comment still be > needed? >=20 I think we need a comment at least. The linkage between the laundrette and the nfsd_serv being set to NULL is very subtle. A READ_ONCE() doesn't convey that well, and is unnecessary here. > Otherwise: >=20 > Reviewed-by: NeilBrown >=20 Thanks! >=20 > > + if (serv) > > + svc_wake_up(serv); > > } > > } > > =20 > >=20 > > --- > > base-commit: 7541a5b8073cf0d9e2d288cac581f1aa6c11671d > > change-id: 20250125-kdevops-0989825ae8db > >=20 > > Best regards, > > --=20 > > Jeff Layton > >=20 > >=20 >=20 --=20 Jeff Layton