Re: [linux-lvm] [PATCH] dmsetup: fix sscanf return check

[Alasdair G Kergon <agk@redhat.com>]

On Thu, Aug 23, 2012 at 02:31:02PM +0100, Matthew Booth wrote:
> -	if (sscanf(ptr, "%llu %llu %s %n",
> -		   &start, &size, ttype, &n) < 3) {
> +	if (sscanf(ptr, "%llu %llu %s %n", &start, &size, ttype, &n) != 4) {

Did you test this?

According to the sscanf man page:

       n      Nothing is expected; instead, the number of characters  consumed
              thus  far  from  the  input  is stored through the next pointer,
              which must be a pointer to  int.   This  is  not  a  conversion,
              although  it can be suppressed with the * assignment-suppression
              character.  The C standard says: "Execution of  a  %n  directive
              does  not increment the assignment count returned at the comple-
              tion of execution" but the Corrigendum seems to contradict this.
              Probably it is wise not to make any assumptions on the effect of
              %n conversions on the return value.

Alasdair