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Re: [libvirt] [PATCH 2/5] openvzGetProcessInfo: address clang-detected low-probability flaw



On 04/14/2010 02:46 AM, Jim Meyering wrote:
> From: Jim Meyering <meyering redhat com>
> 
> * src/openvz/openvz_driver.c (openvzGetProcessInfo): Reorganize
> so that unexpected /proc/vz/vestat content cannot make us use
> uninitialized variables.  Without this change, an input line with
> a matching "readvps", but fewer than 4 numbers would result in our
> using at least "systime" uninitialized.
> ---
>  src/openvz/openvz_driver.c |   30 +++++++++++++++---------------
>  1 files changed, 15 insertions(+), 15 deletions(-)
> 
> diff --git a/src/openvz/openvz_driver.c b/src/openvz/openvz_driver.c
> index 95c4236..47004d6 100644
> --- a/src/openvz/openvz_driver.c
> +++ b/src/openvz/openvz_driver.c
> @@ -1384,14 +1384,15 @@ static int openvzGetProcessInfo(unsigned long long *cpuTime, int vpsid) {
>      int fd;
>      char line[1024] ;
>      unsigned long long usertime, systime, nicetime;
> -    int readvps = 0, ret;
> +    int readvps = vpsid + 1;  /* ensure readvps is initially different */
> +    int ret;
> 
> -        if (sscanf(line, "%d %llu %llu %llu",
> -                          &readvps, &usertime, &nicetime, &systime) != 4)
> -            continue;
> -
> -        if (readvps == vpsid)
> -            break; /*found vpsid*/
> +        if (sscanf (line, "%d %llu %llu %llu",
> +                    &readvps, &usertime, &nicetime, &systime) == 4
> +            && readvps == vpsid) { /*found vpsid*/
> +            /* convert jiffies to nanoseconds */
> +            *cpuTime = (1000ull * 1000ull * 1000ull
> +                        * (usertime + nicetime  + systime)
> +                        / (unsigned long long)sysconf(_SC_CLK_TCK));
> +            break;
> +        }

ACK that the rewrite fixes the problem.  However, there's still the
issue that we're using sscanf in the first place, instead of
virStrToLong_ull; do you want to prepare a followup patch, or shall I?

-- 
Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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