From: Colin Ian King <colin.king@canonical.com>
To: "J . Bruce Fields" <bfields@fieldses.org>,
Dan Carpenter <dan.carpenter@oracle.com>
Cc: Ari Kauppi <ari@synopsys.com>,
Jeff Layton <jlayton@poochiereds.net>,
linux-nfs@vger.kernel.org, kernel-janitors@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] nfsd: avoid out of bounds read on array nfsd4_layout_ops
Date: Tue, 9 May 2017 22:14:48 +0100 [thread overview]
Message-ID: <5d21cd12-c842-d0ce-34bb-f037d0fd52ba@canonical.com> (raw)
In-Reply-To: <20170509210350.GD6289@fieldses.org>
On 09/05/17 22:03, J . Bruce Fields wrote:
> On Tue, May 09, 2017 at 05:04:14PM +0300, Dan Carpenter wrote:
>> On Tue, May 09, 2017 at 02:31:21PM +0100, Colin King wrote:
>>> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
>>> index 1dbf62190bee..c453a1998e00 100644
>>> --- a/fs/nfsd/nfs4proc.c
>>> +++ b/fs/nfsd/nfs4proc.c
>>> @@ -1259,7 +1259,8 @@ nfsd4_layout_verify(struct svc_export *exp, unsigned int layout_type)
>>> return NULL;
>>> }
>>>
>>> - if (layout_type >= 32 || !(exp->ex_layout_types & (1 << layout_type))) {
>>> + if (layout_type >= LAYOUT_TYPE_MAX ||
>>> + !(exp->ex_layout_types & (1 << layout_type))) {
>>
>> The 32 is there to prevent a shift wrapping bug. The bit test prevents
>> a buffer overflow so this can't actually overflow.
>
> Yes, looks like a false positive for coverity.
>
>> But this change doesn't hurt and is probably cleaner.
>
> Sure. Hope it's OK if I just merge this into the previous commit:
Fine by me. Colin
>
> --b.
>
> commit 16b6f81d8ed9
> Author: Ari Kauppi <ari@synopsys.com>
> Date: Fri May 5 16:07:55 2017 -0400
>
> nfsd: fix undefined behavior in nfsd4_layout_verify
>
> UBSAN: Undefined behaviour in fs/nfsd/nfs4proc.c:1262:34
> shift exponent 128 is too large for 32-bit type 'int'
>
> Depending on compiler+architecture, this may cause the check for
> layout_type to succeed for overly large values (which seems to be the
> case with amd64). The large value will be later used in de-referencing
> nfsd4_layout_ops for function pointers.
>
> Reported-by: Jani Tuovila <tuovila@synopsys.com>
> Signed-off-by: Ari Kauppi <ari@synopsys.com>
> [colin.king@canonical.com: use LAYOUT_TYPE_MAX instead of 32]
> Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
>
> diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
> index d86031b6ad79..c453a1998e00 100644
> --- a/fs/nfsd/nfs4proc.c
> +++ b/fs/nfsd/nfs4proc.c
> @@ -1259,7 +1259,8 @@ nfsd4_layout_verify(struct svc_export *exp, unsigned int layout_type)
> return NULL;
> }
>
> - if (!(exp->ex_layout_types & (1 << layout_type))) {
> + if (layout_type >= LAYOUT_TYPE_MAX ||
> + !(exp->ex_layout_types & (1 << layout_type))) {
> dprintk("%s: layout type %d not supported\n",
> __func__, layout_type);
> return NULL;
> --
> To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
next prev parent reply other threads:[~2017-05-09 21:14 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-05-09 13:31 [PATCH] nfsd: avoid out of bounds read on array nfsd4_layout_ops Colin King
2017-05-09 14:04 ` Dan Carpenter
2017-05-09 21:03 ` J . Bruce Fields
2017-05-09 21:14 ` Colin Ian King [this message]
2017-05-10 5:24 ` Ari Kauppi
2017-05-09 19:57 ` Christoph Hellwig
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