linux-kernel - re: xprtrdma: Prevent inline overflow

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Date:   Wed, 15 Jul 2020 16:56:58 +0100
From:   Colin Ian King <colin.king@...onical.com>
To:     Trond Myklebust <trond.myklebust@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        "J. Bruce Fields" <bfields@...ldses.org>,
        Chuck Lever <chuck.lever@...cle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: re: xprtrdma: Prevent inline overflow

Hi,

Static analysis with Coverity has found a potential issue with the
header size calculations in source net/sunrpc/xprtrdma/rpc_rdma.c in
functions rpcrdma_max_call_header_size and rpcrdma_max_reply_header_size.

The commit in question is relatively old:

commit 302d3deb20682a076e1ab551821cacfdc81c5e4f
Author: Chuck Lever <chuck.lever@...cle.com>
Date:   Mon May 2 14:41:05 2016 -0400

    xprtrdma: Prevent inline overflow

The two issues are as follows:

Issue #1:

66 static unsigned int rpcrdma_max_call_header_size(unsigned int maxsegs)
 67 {
 68        unsigned int size;
 69
 70        /* Fixed header fields and list discriminators */

Unused value (UNUSED_VALUE)

 71        size = RPCRDMA_HDRLEN_MIN;
 72
 73        /* Maximum Read list size */
 74        size = maxsegs * rpcrdma_readchunk_maxsz * sizeof(__be32);
 75

should the size assignment on line 74 be instead:

	size += maxsegs * rpcrdma_readchunk_maxsz * sizeof(__be32);


Issue #2:

 89 static unsigned int rpcrdma_max_reply_header_size(unsigned int maxsegs)
 90 {
 91        unsigned int size;
 92
 93        /* Fixed header fields and list discriminators */

Unused value (UNUSED_VALUE)

 94        size = RPCRDMA_HDRLEN_MIN;
 95
 96        /* Maximum Write list size */
 97        size = sizeof(__be32);          /* segment count */

should the size assignment in line 97 be instead:

 	size += sizeof(__be32)?


Colin