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 4F415481FC3; Mon, 18 May 2026 16:39:04 +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=1779122344; cv=none; b=uX7bCUmq6eHKIS/tas2cdmXftImSkisnoYPtqWOkdb8cb+EuZyFiUH0tJYj2V3uvnCZWBAk4z0DvCpIEfKVcl6ZSWqp245b6xq2pYiYSSufGmNb/+7D+e1FbSWJ2vDcn88xzY67EKMzCV/sMxsFDXP53vOQps/rYpeQ7bpawQUo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1779122344; c=relaxed/simple; bh=vkd4n2uLtpskcD9P2mHpbZ5qBTWRyq5ZnMXww/McnEk=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=Ob0zR16b2IdH/Ui9nGVhqRLpOuSud9H/ueMuQ/kUxwVLenmA/XI/6F9Yfb0+7oYRXhb/A8FgIMoK1v0QOy6tzdCgdmFb7F5xUtylGT5i5zz8kndigPgaTV7a1MvoEORzLB1Vue1AsfeIr0lv5tvMLhw0pRXLieqJl/AfkWJbJ0c= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=R41+eDtJ; 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="R41+eDtJ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 35D7FC2BCB7; Mon, 18 May 2026 16:39:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1779122344; bh=vkd4n2uLtpskcD9P2mHpbZ5qBTWRyq5ZnMXww/McnEk=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=R41+eDtJQZssXuugd8l8D1HhdURWDcAtCunzxtez+t9Q1mqqTFmxoIZKycqTqb5XY 9Ddl35lKWOOXWy23BJMYil+glP6RVdUm1kd8VHAX3uRFcfgin1JsCC7JJZxDfJ+4qC FVWmEGpteD0Y7RjNxXDNeX3pwFyDs96pPz0n0+qitt5h0CSe7NBrnJfbvcUswingo9 r93rvT85+lfqc3MtMOQo21S5HPCV23wLahIggnKVxzuoovsEGAAlumc8CL5Zb1aH/8 MxR4mgGyGuaZeo/kauROtOJpXqz7LlBqCVPs8EAzx2XCwKu85LOrvkCoyQhMe1A2/T pPRxXmODtk5bA== Message-ID: <1013d4caa10d79eeab095ca51cdc4f243d6eb798.camel@kernel.org> Subject: Re: [PATCH] nfsd: fix use-after-free in nfsd4_lock() when releasing new lock stateid From: Jeff Layton To: Wentao Liang , Chuck Lever Cc: NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey , linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Date: Mon, 18 May 2026 12:39:00 -0400 In-Reply-To: <20260518153048.1343021-1-vulab@iscas.ac.cn> References: <20260518153048.1343021-1-vulab@iscas.ac.cn> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV 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Mon, 2026-05-18 at 15:30 +0000, Wentao Liang wrote: > When processing a new lock request that fails with an error, > nfsd4_lock() may call release_lock_stateid() on a newly created > lock stateid. release_lock_stateid() can free the stateid via > nfs4_put_stid() if it is the last reference, but the caller > subsequently accesses lock_stp->st_mutex and lock_stp->st_stid, > leading to a use-after-free. >=20 > Fix this by moving mutex_unlock() before release_lock_stateid() > and jumping over the remaining lock_stp cleanup after release, > since release_lock_stateid() already handles the final put. > This ensures no further access to lock_stp after it may be freed. >=20 > Fixes: 5db1c03feb00 ("nfsd: clean up lockowner refcounting when finding t= hem") > Cc: stable@vger.kernel.org > Signed-off-by: Wentao Liang > --- > fs/nfsd/nfs4state.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) >=20 > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index 88c347957da5..cef9d8ddfc43 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -8388,13 +8388,18 @@ nfsd4_lock(struct svc_rqst *rqstp, struct nfsd4_c= ompound_state *cstate, > * If this is a new, never-before-used stateid, and we are > * returning an error, then just go ahead and release it. > */ > - if (status && new) > + if (status && new) { > + mutex_unlock(&lock_stp->st_mutex); > release_lock_stateid(lock_stp); > + goto out_no_lock_stp; > + } > =20 > mutex_unlock(&lock_stp->st_mutex); > =20 > nfs4_put_stid(&lock_stp->st_stid); > } > + > +out_no_lock_stp: > if (open_stp) > nfs4_put_stid(&open_stp->st_stid); > nfsd4_bump_seqid(cstate, status); This patch is not correct. It's not terribly obvious, but at the point of the start of the delta, lock_stp has a refcount of 2, so this problem can't happen: 1. nfs4_alloc_stid() =E2=80=94 sets sc_count =3D 1 2. init_lock_stateid() line 8193 =E2=80=94 refcount_inc(&stp->st_stid.sc_= count) =E2=86=92 sc_count =3D 2 I don't think there is a bug here. --=20 Jeff Layton