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From:   Shyam Prasad N <nspmangalore@gmail.com>
Date:   Mon, 22 May 2023 22:58:39 +0530
Message-ID: <CANT5p=pNFpEj0p+njYw3sVdq9CKgsTdh29Gj6iYDOsMN0ocj1Q@mail.gmail.com>
Subject: Re: [PATCH] cifs: Fix cifs_limit_bvec_subset() to correctly check the
 maxmimum size
To:     David Howells <dhowells@redhat.com>
Cc:     Shyam Prasad N <sprasad@microsoft.com>,
        Steve French <smfrench@gmail.com>,
        Rohith Surabattula <rohiths.msft@gmail.com>,
        Paulo Alcantara <pc@manguebit.com>,
        Tom Talpey <tom@talpey.com>, Jeff Layton <jlayton@kernel.org>,
        linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        linux-kernel@vger.kernel.org
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On Mon, May 22, 2023 at 8:22=E2=80=AFPM David Howells <dhowells@redhat.com>=
 wrote:
>
> Fix cifs_limit_bvec_subset() so that it limits the span to the maximum
> specified and won't return with a size greater than max_size.
>
> Fixes: d08089f649a0 ("cifs: Change the I/O paths to use an iterator rathe=
r than a page list")
> Reported-by: Shyam Prasad N <sprasad@microsoft.com>
> Signed-off-by: David Howells <dhowells@redhat.com>
> cc: Steve French <smfrench@gmail.com>
> cc: Rohith Surabattula <rohiths.msft@gmail.com>
> cc: Paulo Alcantara <pc@manguebit.com>
> cc: Tom Talpey <tom@talpey.com>
> cc: Jeff Layton <jlayton@kernel.org>
> cc: linux-cifs@vger.kernel.org
> cc: linux-fsdevel@vger.kernel.org
> ---
>  fs/cifs/file.c |    1 +
>  1 file changed, 1 insertion(+)
>
>
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index ba7f2e09d6c8..4778614cfccf 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -3353,6 +3353,7 @@ static size_t cifs_limit_bvec_subset(const struct i=
ov_iter *iter, size_t max_siz
>         while (n && ix < nbv) {
>                 len =3D min3(n, bvecs[ix].bv_len - skip, max_size);
>                 span +=3D len;
> +               max_size -=3D len;

Shouldn't this decrement happen below, after the span has been
compared with max_size?

>                 nsegs++;
>                 ix++;
>                 if (span >=3D max_size || nsegs >=3D max_segs)
>


--=20
Regards,
Shyam