From patchwork Tue Dec 31 00:28:54 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Chuck Lever X-Patchwork-Id: 13923569 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 AA0DEB660 for ; Tue, 31 Dec 2024 00:29:08 +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=1735604948; cv=none; b=LLg6cq5a7y8s5BIPsTn2LGC+BklkKSPtTYUNtgXBGBvEAYaNGji6DK2XC8OKUTsRgLjjUPj/hRgpJxeQCzanC3JpyrB7O06MpPW1suRreDYJjUbI0NJIM1BFDu07PkAPfeQM/DapVOGOBxydJMA5aar7IHdMVCZO1cawGu4FkV4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735604948; c=relaxed/simple; bh=JaWDDhfb+mmrwo7+SaQV+zwajMn+Ijykp/ajU/NijbI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=EcCfkVxaVUi0do++ymxLI+wCBZypFqLNKg8iskBFs5nHB1UZfVRyLOcAK429Qi5Fg8a/PPwBUjSrEi0f9KH1/5vZUKIk6skaUPaheEpZUYsXVl7oPslUXfZG07U+z+EExKC0+xNuZL7Qn4cSkEbqWZ6zeyhGggtAxorMrbxF9wo= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=ZWP8aD/C; 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="ZWP8aD/C" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B1A04C4CEDC; Tue, 31 Dec 2024 00:29:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1735604948; bh=JaWDDhfb+mmrwo7+SaQV+zwajMn+Ijykp/ajU/NijbI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=ZWP8aD/CGKdeP9OMK3YXigdx/QSxOmLNSEATGeCnIJaG7DX+ipIRPtg2L/M8o7vRu aBic9iVVCpJt9t490ptkQ39B6j2oLM5DdvuZd+P/yMn7uWCE8YaNQAyioNRA8HxUIX +FezGSHsIOH3vPTfPoimm7T/1nmu7c8Y9rMtXff2Tc5HiREQfMeVC2RgW8Xbeft43S KtUjvZtd9d1QfWYTxWgHDUjh4y1YkhmeeZyIomvE8TJC/ichz2LqNdioxojRTef6L8 ib6muMNo2AY93IMP6opxrbW/DxanjnEm57yfT2swtkAmc3UQLXlz+pCWoF+F51xcBY W1lSgyY3hJeKg== From: cel@kernel.org To: Neil Brown , Jeff Layton , Olga Kornievskaia , Dai Ngo , Tom Talpey Cc: , Rick Macklem , j.david.lists@gmail.com, Chuck Lever Subject: [PATCH v4 3/9] NFSD: Insulate nfsd4_encode_read_plus() from page boundaries in the encode buffer Date: Mon, 30 Dec 2024 19:28:54 -0500 Message-ID: <20241231002901.12725-4-cel@kernel.org> X-Mailer: git-send-email 2.47.0 In-Reply-To: <20241231002901.12725-1-cel@kernel.org> References: <20241231002901.12725-1-cel@kernel.org> Precedence: bulk X-Mailing-List: linux-nfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Chuck Lever Commit eeadcb757945 ("NFSD: Simplify READ_PLUS") replaced the use of write_bytes_to_xdr_buf(), copying what was in nfsd4_encode_read() at the time. However, the current code will corrupt the encoded data if the XDR data items that are reserved early and then poked into the XDR buffer later happen to fall on a page boundary in the XDR encoding buffer. __xdr_commit_encode can shift encoded data items in the encoding buffer so that pointers returned from xdr_reserve_space() no longer address the same part of the encoding stream. Fixes: eeadcb757945 ("NFSD: Simplify READ_PLUS") Signed-off-by: Chuck Lever --- fs/nfsd/nfs4xdr.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c index 094806fe1a32..00e2f4fc4e19 100644 --- a/fs/nfsd/nfs4xdr.c +++ b/fs/nfsd/nfs4xdr.c @@ -5336,16 +5336,17 @@ nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr, struct nfsd4_read *read = &u->read; struct file *file = read->rd_nf->nf_file; struct xdr_stream *xdr = resp->xdr; - int starting_len = xdr->buf->len; + unsigned int eof_offset; + __be32 wire_data[2]; u32 segments = 0; - __be32 *p; if (nfserr) return nfserr; - /* eof flag, segment count */ - p = xdr_reserve_space(xdr, 4 + 4); - if (!p) + eof_offset = xdr_stream_pos(xdr); + + /* Reserve space for the eof flag and segment count */ + if (unlikely(!xdr_reserve_space(xdr, XDR_UNIT * 2))) return nfserr_io; xdr_commit_encode(xdr); @@ -5355,15 +5356,16 @@ nfsd4_encode_read_plus(struct nfsd4_compoundres *resp, __be32 nfserr, nfserr = nfsd4_encode_read_plus_data(resp, read); if (nfserr) { - xdr_truncate_encode(xdr, starting_len); + xdr_truncate_encode(xdr, eof_offset); return nfserr; } segments++; out: - p = xdr_encode_bool(p, read->rd_eof); - *p = cpu_to_be32(segments); + wire_data[0] = read->rd_eof ? xdr_one : xdr_zero; + wire_data[1] = cpu_to_be32(segments); + write_bytes_to_xdr_buf(xdr->buf, eof_offset, &wire_data, XDR_UNIT * 2); return nfserr; }