linux-kernel - Re: [PATCH] nfs: Added pointer check

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Message-ID: <C675D59D-0684-4956-81F6-FC9602EF2698@hammerspace.com>
Date:   Tue, 6 Dec 2022 15:30:19 +0000
From:   Trond Myklebust <trondmy@...merspace.com>
To:     Denis Arefev <arefev@...mel.ru>
CC:     Trond Myklebust <trondmy@...merspace.com>,
        Anna Schumaker <anna.schumaker@...app.com>,
        Linux NFS Mailing List <linux-nfs@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "lvc-project@...uxtesting.org" <lvc-project@...uxtesting.org>,
        "trufanov@...mel.ru" <trufanov@...mel.ru>,
        "vfh@...mel.ru" <vfh@...mel.ru>
Subject: Re: [PATCH] nfs: Added pointer check



> On Dec 6, 2022, at 04:26, Denis Arefev <arefev@...mel.ru> wrote:
> 
> Return value of a function 'xdr_inline_decode' is dereferenced at
> nfs4xdr.c:5540 without checking for null,
> ut it is usually checked for this function
> 
> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> 
> Signed-off-by: Denis Arefev <arefev@...mel.ru>
> ---
> fs/nfs/nfs4xdr.c | 2 ++
> 1 file changed, 2 insertions(+)
> 
> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
> index c6dbfcae7517..571cc63ecb61 100644
> --- a/fs/nfs/nfs4xdr.c
> +++ b/fs/nfs/nfs4xdr.c
> @@ -5533,6 +5533,8 @@ static int decode_op_map(struct xdr_stream *xdr, struct nfs4_op_map *op_map)
> if (bitmap_words > NFS4_OP_MAP_NUM_WORDS)
> return -EIO;
> p = xdr_inline_decode(xdr, 4 * bitmap_words);
> + if (!p)
> + return -EIO;
> for (i = 0; i < bitmap_words; i++)
> op_map->u.words[i] = be32_to_cpup(p++);
> 
> -- 
> 2.25.1
> 


Again… What kernel is this for? The current code was introduced in Linux 5.16, and looks like this:

static int decode_op_map(struct xdr_stream *xdr, struct nfs4_op_map *op_map)
{
        if (xdr_stream_decode_uint32_array(xdr, op_map->u.words,
                                           ARRAY_SIZE(op_map->u.words)) < 0)
                return -EIO;
        return 0;
}

It does not have the problem you keep trying to report, and you patch doesn’t apply.

_________________________________
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@...merspace.com