From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 A9058392C46 for ; Fri, 9 Oct 2026 16:50:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791564653; cv=none; b=JYkGEilaCTY+4O5FSrL4t0nzN53qxBINx2y+qsLp/rKUJf0+WFeHYHalFWgr8BxihIvhf74sHTIDr75COAZdD1nwtmzoOLnwooA7XfHUUfHzRzzsmRqmXpR1cHkwMd2MVrfkYhEtYcn9bWLSNir5DgM9wmE74vPE8bvEPdYp/bo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791564653; c=relaxed/simple; bh=m7VZoj+K3JznXwu8AG0oVtNqLg4y97jJr9RLW4PP8wM=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=uD+kCw5oGmEPldrOapRxl6D162xDNhtjGyhUtFsd/V0Y97YsoCwhg1EPy+wf5zuLokv+5WPni6t2ni2JL7o9YD3plpz65DD5dwatiogglOmtWdK+r0Jfg+FzPds5xdVEbxlW7rX7fL1vOvcMivDOeIkqtXKkgytsXbG/XOt1Xrs= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=K7nNZhng; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="K7nNZhng" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C71F51F000FF; Fri, 9 Oct 2026 16:50:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1791564652; bh=KDHwxZkL/AY1JqSS1qpz+BJQI+bCKauJnIOy1uz/t0k=; h=Subject:From:To:Cc:Date:In-Reply-To:References; b=K7nNZhngFVcEJzzfeV/PDdVFAfUsbCV8vewtu7I+QMTyn3iNqxkpdIRIa6gbCYIMV IC/g+LIrCb9YmtRf/IlN7YhchwO21CAW+7SiSybFGCUnQv0nkWukg/OYoKQx2B3xo5 OiBkLI/Ue1Xr5zJ3+4njifQsADOjZyFKWdKQixnAKXslTjut3CEwtUwiTxyku5Evuv 9SkOONoECwoBX/egR27OHWJY4ZxwZcb/S3OKpeDYpw/+sjdWahPscyz4RwVsvNzu/Q 5ZK4K2k5reAf0bwPxleugjlMxmGm0a3voOEcfDRgz7EISu73nSDwWbcxKhF+1zMT6M qSCGZx3FFMI4g== Message-ID: <2da460c2585851e2c4de977b5bdb5ea1bd5175a3.camel@kernel.org> Subject: Re: [PATCH v1] NFSD: Don't start nfsd threads from a pool_threads write From: Jeff Layton To: Chuck Lever , NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: linux-nfs@vger.kernel.org, syzbot+9c7b9c5f6dd1d470b605@syzkaller.appspotmail.com Date: Fri, 09 Oct 2026 12:50:49 -0400 In-Reply-To: <20261009144017.1284586-1-cel@kernel.org> References: <20261009144017.1284586-1-cel@kernel.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 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calls nfsd_set_nrthreads() directly, which > starts nfsd threads as soon as a svc_serv exists. A portlist write > creates the svc_serv without running nfsd_startup_net(), so a > pool_threads write that follows it starts threads in a namespace > whose NFSv4 state has not been set up. If the server in that > namespace has been started and shut down before, the hash table > pointers in struct nfsd_net still point at memory that > nfs4_state_destroy_net() freed, and the first EXCHANGE_ID those > threads handle reads it: >=20 > BUG: KASAN: slab-use-after-free in add_to_unconfirmed > nfsd4_exchange_id > nfsd4_proc_compound > nfsd_dispatch >=20 > A namespace that has never been started dereferences NULL instead. >=20 > write_pool_threads() already starts nothing when no svc_serv exists, > and its comment documents that only the threads file starts NFS. > Ignore the thread counts in a pool_threads write while NFSD_NET_UP > is clear as well, so a pool_threads write never starts threads > before nfsd_startup_net() has run. The reply still reports the > current thread count for each pool. >=20 > Fixes: 0a7ec37727dc ("nfsd: make unconf_id_hashtbl allocated per net") > Reported-by: syzbot+9c7b9c5f6dd1d470b605@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=3D9c7b9c5f6dd1d470b605 > Signed-off-by: Chuck Lever > --- > fs/nfsd/nfsctl.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) >=20 > diff --git a/fs/nfsd/nfsctl.c b/fs/nfsd/nfsctl.c > index 2379b838c028..5a606086b811 100644 > --- a/fs/nfsd/nfsctl.c > +++ b/fs/nfsd/nfsctl.c > @@ -497,7 +497,8 @@ static ssize_t write_pool_threads(struct file *file, = char *buf, size_t size) > if (nthreads =3D=3D NULL) > goto out_free; > =20 > - if (size > 0) { > + /* Threads started now would run without NFSv4 state. */ > + if (size > 0 && test_bit(NFSD_NET_UP, &nn->flags)) { > for (i =3D 0; i < npools; i++) { > rv =3D get_int(&mesg, &nthreads[i]); > if (rv =3D=3D -ENOENT) Reviewed-by: Jeff Layton