Re: [libvirt] [PATCH] nwfilter: Fix sscanf off-by-one error in virNWFilterSnoopLeaseFileLoad
On 06/02/2015 11:35 AM, Martin Kletzander wrote:
On Tue, Jun 02, 2015 at 10:18:34AM +0200, Erik Skultety wrote:
> We allocate 16 bytes for IPv4 address and 55 bytes for interface
> key, therefore we should read up to 15/54 bytes and let the last byte
> reserved for terminating null byte in sscanf.
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1226400
> ---
> src/nwfilter/nwfilter_dhcpsnoop.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/src/nwfilter/nwfilter_dhcpsnoop.c
> b/src/nwfilter/nwfilter_dhcpsnoop.c
> index 6da8983..f331e22 100644
> --- a/src/nwfilter/nwfilter_dhcpsnoop.c
> +++ b/src/nwfilter/nwfilter_dhcpsnoop.c
> @@ -1958,8 +1958,8 @@ virNWFilterSnoopLeaseFileLoad(void)
> break;
> }
> ln++;
> - /* key len 55 = "VMUUID"+'-'+"MAC" */
> - if (sscanf(line, "%u %55s %16s %16s", &ipl.timeout,
> + /* key len 54 = "VMUUID"+'-'+"MAC" */
> + if (sscanf(line, "%u %54s %15s %15s", &ipl.timeout,
> ifkey, ipstr, srvstr) < 4) {
We initialize ifkey as char ifkey[VIR_IFKEY_LEN], so it might be nicer
to call:
if (sscanf(line, "%u %*s %*s %*s", &ipl.timeout,
VIR_IFKEY_LEN - 1, ifkey,
INET_ADDRSTRLEN - 1, ipstr,
INET_ADDRSTRLEN - 1, srvstr) < 4) {
...
I'd like to disagree --> 'error: too many arguments for format',
perhaps
you've mistaken this for printf where man says:
"Instead of a decimal digit string one may write "*" or "*m$"
(for some
decimal integer m) to specify that the field width is given in the next
argument, or in the m-th argument, respectively, which must be of type int."
This however is different for scanf, where '*' is defined as
assignment-suppression character
But what you have is enough, so ACK to that.
Thanks for the ACK
though.
Regards,
Erik