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 6EDB030DEB8 for ; Tue, 24 Feb 2026 19:39:52 +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=1771961992; cv=none; b=ga0LM1YEmEEln+poMl2yEryB/MOrodIGadxM3HX56SNRo58zTgiSMtXXx4rQSNapp4uxIrQf2OkBkT/rH3hhFgbTrbT6gPWkwBC06cAHRiYFWDI8v6pU1lc5bE89gUVswARLytGMhwC0Fzq4OLI7LeWc+CDUmIduodx+xwdgVMs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771961992; c=relaxed/simple; bh=tBdEPlIif6gKTkdYVy0GUsL0Hn+EpZenDifff/vFc3A=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=YH4Z/TmM3BSS+iTG0fx2bzKHr0jKo5cAecOFqaDpOhoCAX1XCC5i+w3Q7o3C814u1n/AC+u48IoGQM8C+K8x6m9VoBcSpfg1aiTxByGPBc+C+c0BfX/RCTIhzZBBnSVFlqzUCiVHe8WU+dcp68asxqk31Uueg4H+97om3Fb05IE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BpPRF5yG; 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="BpPRF5yG" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 54190C116D0; Tue, 24 Feb 2026 19:39:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1771961992; bh=tBdEPlIif6gKTkdYVy0GUsL0Hn+EpZenDifff/vFc3A=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=BpPRF5yGRECtBLPYFYUc/z9yYMF+DKZmjQR5EIJCE697jbcoWbjiz242Ox1KU5+bK JvE7ijDKWOfrYu/TjNaekfeo7yKEIRBHiQZoNN0fRYHSQfJ1D0+Sfq9JjQmJqoEWR4 Yy+TuOD+2Q9Rn4b1W8+9SJJbtzhOs3CKoRXOHKrZOkK1KiOKVnf8N03ZZfQyoYbyXA T5ZSoaEkc+mTc9UN2OvOxpqL8W7kQ7hIx9QfUnpoKp2VBrsG0wtfjohpTXafHAo8Ts nGS6u+70qfoUmcD6a/oh6TeoQJGfv3BIFk3kQ1OmzeBdv1ynuwLEY6QvcYqnp1BXHS lm/bxUG9aVLSg== Message-ID: <887c1ca78b34974160dee3ce7f25d6d077da93ab.camel@kernel.org> Subject: Re: [PATCH] nfsd: use dynamic allocation for oversized NFSv4.0 replay cache From: Jeff Layton To: Chuck Lever Cc: NeilBrown , Olga Kornievskaia , Dai Ngo , Tom Talpey , linux-nfs@vger.kernel.org, Chuck Lever Date: Tue, 24 Feb 2026 14:39:50 -0500 In-Reply-To: <20260224193354.57849-1-cel@kernel.org> References: <20260224193354.57849-1-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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Commit 1e8e9913672a ("nfsd: fix heap overflow in NFSv4.0 LOCK > replay cache") capped the replay cache copy at NFSD4_REPLAY_ISIZE > to prevent a heap overflow, but set rp_buflen to zero when the > encoded response exceeded the inline buffer. A retransmitted LOCK > reaching the replay path then produced only a status code with no > operation body, resulting in a malformed XDR response. >=20 > When the encoded response exceeds the 112-byte inline rp_ibuf, a > buffer is kmalloc'd to hold it. If the allocation fails, rp_buflen > remains zero, preserving the behavior from the capped-copy fix. > The buffer is freed when the stateowner is released or when a > subsequent operation's response fits in the inline buffer. >=20 > Fixes: 1e8e9913672a ("nfsd: fix heap overflow in NFSv4.0 LOCK replay cach= e") > Signed-off-by: Chuck Lever > --- > fs/nfsd/nfs4state.c | 16 ++++++++++++++++ > fs/nfsd/nfs4xdr.c | 23 ++++++++++++++++------- > fs/nfsd/state.h | 12 +++++++----- > 3 files changed, 39 insertions(+), 12 deletions(-) >=20 > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c > index ba49f49bb93b..b4d0e82b2690 100644 > --- a/fs/nfsd/nfs4state.c > +++ b/fs/nfsd/nfs4state.c > @@ -1496,8 +1496,24 @@ release_all_access(struct nfs4_ol_stateid *stp) > } > } > =20 > +/** > + * nfs4_replay_free_cache - release dynamically allocated replay buffer > + * @rp: replay cache to reset > + * > + * If @rp->rp_buf points to a kmalloc'd buffer, free it and reset > + * rp_buf to the inline rp_ibuf. Always zeroes rp_buflen. > + */ > +void nfs4_replay_free_cache(struct nfs4_replay *rp) > +{ > + if (rp->rp_buf !=3D rp->rp_ibuf) > + kfree(rp->rp_buf); > + rp->rp_buf =3D rp->rp_ibuf; > + rp->rp_buflen =3D 0; > +} > + > static inline void nfs4_free_stateowner(struct nfs4_stateowner *sop) > { > + nfs4_replay_free_cache(&sop->so_replay); > kfree(sop->so_owner.data); > sop->so_ops->so_free(sop); > } > diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c > index 690f7a3122ec..2a0946c630e1 100644 > --- a/fs/nfsd/nfs4xdr.c > +++ b/fs/nfsd/nfs4xdr.c > @@ -6282,14 +6282,23 @@ nfsd4_encode_operation(struct nfsd4_compoundres *= resp, struct nfsd4_op *op) > int len =3D xdr->buf->len - (op_status_offset + XDR_UNIT); > =20 > so->so_replay.rp_status =3D op->status; > - if (len <=3D NFSD4_REPLAY_ISIZE) { > - so->so_replay.rp_buflen =3D len; > - read_bytes_from_xdr_buf(xdr->buf, > - op_status_offset + XDR_UNIT, > - so->so_replay.rp_buf, len); > - } else { > - so->so_replay.rp_buflen =3D 0; > + if (len > NFSD4_REPLAY_ISIZE) { > + char *buf =3D kmalloc(len, GFP_KERNEL); > + > + nfs4_replay_free_cache(&so->so_replay); > + if (buf) { > + so->so_replay.rp_buf =3D buf; > + } else { > + /* rp_buflen already zeroed; skip caching */ > + goto status; > + } > + } else if (so->so_replay.rp_buf !=3D so->so_replay.rp_ibuf) { > + nfs4_replay_free_cache(&so->so_replay); > } > + so->so_replay.rp_buflen =3D len; > + read_bytes_from_xdr_buf(xdr->buf, > + op_status_offset + XDR_UNIT, > + so->so_replay.rp_buf, len); > } > status: > op->status =3D nfsd4_map_status(op->status, > diff --git a/fs/nfsd/state.h b/fs/nfsd/state.h > index 3159c7b67f50..9b05462da4cc 100644 > --- a/fs/nfsd/state.h > +++ b/fs/nfsd/state.h > @@ -554,10 +554,10 @@ struct nfs4_client_reclaim { > * ~32(deleg. ace) =3D 112 bytes > * > * Some responses can exceed this. A LOCK denial includes the conflictin= g > - * lock owner, which can be up to 1024 bytes (NFS4_OPAQUE_LIMIT). Respon= ses > - * larger than REPLAY_ISIZE are not cached in rp_ibuf; only rp_status is > - * saved. Enlarging this constant increases the size of every > - * nfs4_stateowner. > + * lock owner, which can be up to 1024 bytes (NFS4_OPAQUE_LIMIT). When a > + * response exceeds REPLAY_ISIZE, a buffer is dynamically allocated. If > + * that allocation fails, only rp_status is saved. Enlarging this consta= nt > + * increases the size of every nfs4_stateowner. > */ > =20 > #define NFSD4_REPLAY_ISIZE 112=20 > @@ -569,12 +569,14 @@ struct nfs4_client_reclaim { > struct nfs4_replay { > __be32 rp_status; > unsigned int rp_buflen; > - char *rp_buf; > + char *rp_buf; /* rp_ibuf or kmalloc'd */ > struct knfsd_fh rp_openfh; > int rp_locked; > char rp_ibuf[NFSD4_REPLAY_ISIZE]; > }; > =20 > +extern void nfs4_replay_free_cache(struct nfs4_replay *rp); > + > struct nfs4_stateowner; > =20 > struct nfs4_stateowner_operations { Certainly a reasonable approach if we care about full correctness when dealing with a large lockowner on NFSv4.0. Do we? --=20 Jeff Layton