Re: [PATCH] libceph: eliminate unnecessary allocation in process_one_ticket()

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On Mon, 27 Oct 2014, Ilya Dryomov wrote:
> Commit c27a3e4d667f ("libceph: do not hard code max auth ticket len")
> while fixing a buffer overlow tried to keep the same as much of the
> surrounding code as possible and introduced an unnecessary kmalloc() in
> the unencrypted ticket path.  It is likely to fail on huge tickets, so
> get rid of it.
> 
> Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxxx>

Reviewed-by: Sage Weil <sage@xxxxxxxxxx>

> ---
>  net/ceph/auth_x.c |   25 ++++++++++---------------
>  1 file changed, 10 insertions(+), 15 deletions(-)
> 
> diff --git a/net/ceph/auth_x.c b/net/ceph/auth_x.c
> index de6662b14e1f..7e38b729696a 100644
> --- a/net/ceph/auth_x.c
> +++ b/net/ceph/auth_x.c
> @@ -149,6 +149,7 @@ static int process_one_ticket(struct ceph_auth_client *ac,
>  	struct ceph_crypto_key old_key;
>  	void *ticket_buf = NULL;
>  	void *tp, *tpend;
> +	void **ptp;
>  	struct ceph_timespec new_validity;
>  	struct ceph_crypto_key new_session_key;
>  	struct ceph_buffer *new_ticket_blob;
> @@ -208,25 +209,19 @@ static int process_one_ticket(struct ceph_auth_client *ac,
>  			goto out;
>  		}
>  		tp = ticket_buf;
> -		dlen = ceph_decode_32(&tp);
> +		ptp = &tp;
> +		tpend = *ptp + dlen;
>  	} else {
>  		/* unencrypted */
> -		ceph_decode_32_safe(p, end, dlen, bad);
> -		ticket_buf = kmalloc(dlen, GFP_NOFS);
> -		if (!ticket_buf) {
> -			ret = -ENOMEM;
> -			goto out;
> -		}
> -		tp = ticket_buf;
> -		ceph_decode_need(p, end, dlen, bad);
> -		ceph_decode_copy(p, ticket_buf, dlen);
> +		ptp = p;
> +		tpend = end;
>  	}
> -	tpend = tp + dlen;
> +	ceph_decode_32_safe(ptp, tpend, dlen, bad);
>  	dout(" ticket blob is %d bytes\n", dlen);
> -	ceph_decode_need(&tp, tpend, 1 + sizeof(u64), bad);
> -	blob_struct_v = ceph_decode_8(&tp);
> -	new_secret_id = ceph_decode_64(&tp);
> -	ret = ceph_decode_buffer(&new_ticket_blob, &tp, tpend);
> +	ceph_decode_need(ptp, tpend, 1 + sizeof(u64), bad);
> +	blob_struct_v = ceph_decode_8(ptp);
> +	new_secret_id = ceph_decode_64(ptp);
> +	ret = ceph_decode_buffer(&new_ticket_blob, ptp, tpend);
>  	if (ret)
>  		goto out;
>  
> -- 
> 1.7.10.4
> 
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