2018-09-25 14:19:56

by Zhi Li

Subject: [PATCH] getnetconfig.c: fix a BAD_FREE (CWE-763)

Signed-off-by: Zhi Li <[email protected]>
---

https://bugzilla.redhat.com/show_bug.cgi?id=1631614

src/getnetconfig.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/src/getnetconfig.c b/src/getnetconfig.c
index d67d97d..869556d 100644
--- a/src/getnetconfig.c
+++ b/src/getnetconfig.c
@@ -681,6 +681,7 @@ struct netconfig *ncp;
{
struct netconfig *p;
char *tmp;
+ char *t;
u_int i;

if ((tmp=malloc(MAXNETCONFIGLINE)) == NULL)
@@ -700,12 +701,12 @@ struct netconfig *ncp;
*/
*p = *ncp;
p->nc_netid = (char *)strcpy(tmp,ncp->nc_netid);
- tmp = strchr(tmp, 0) + 1;
- p->nc_protofmly = (char *)strcpy(tmp,ncp->nc_protofmly);
- tmp = strchr(tmp, 0) + 1;
- p->nc_proto = (char *)strcpy(tmp,ncp->nc_proto);
- tmp = strchr(tmp, 0) + 1;
- p->nc_device = (char *)strcpy(tmp,ncp->nc_device);
+ t = strchr(tmp, 0) + 1;
+ p->nc_protofmly = (char *)strcpy(t,ncp->nc_protofmly);
+ t = strchr(t, 0) + 1;
+ p->nc_proto = (char *)strcpy(t,ncp->nc_proto);
+ t = strchr(t, 0) + 1;
+ p->nc_device = (char *)strcpy(t,ncp->nc_device);
p->nc_lookups = (char **)malloc((size_t)(p->nc_nlookups+1) * sizeof(char *));
if (p->nc_lookups == NULL) {
free(p->nc_netid);
@@ -714,8 +715,8 @@ struct netconfig *ncp;
return(NULL);
}
for (i=0; i < p->nc_nlookups; i++) {
- tmp = strchr(tmp, 0) + 1;
- p->nc_lookups[i] = (char *)strcpy(tmp,ncp->nc_lookups[i]);
+ t = strchr(t, 0) + 1;
+ p->nc_lookups[i] = (char *)strcpy(t,ncp->nc_lookups[i]);
}
return(p);
}
--
2.7.5

2018-09-25 21:52:08

by Steve Dickson

Subject: Re: [PATCH] getnetconfig.c: fix a BAD_FREE (CWE-763)

On 9/25/18 4:13 AM, Zhi Li wrote:
> Signed-off-by: Zhi Li <[email protected]>
> ---
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1631614
>
> src/getnetconfig.c | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/src/getnetconfig.c b/src/getnetconfig.c
> index d67d97d..869556d 100644
> --- a/src/getnetconfig.c
> +++ b/src/getnetconfig.c
> @@ -681,6 +681,7 @@ struct netconfig *ncp;
> {
> struct netconfig *p;
> char *tmp;
> + char *t;
> u_int i;
>
> if ((tmp=malloc(MAXNETCONFIGLINE)) == NULL)
> @@ -700,12 +701,12 @@ struct netconfig *ncp;
> */
> *p = *ncp;
> p->nc_netid = (char *)strcpy(tmp,ncp->nc_netid);
> - tmp = strchr(tmp, 0) + 1;
> - p->nc_protofmly = (char *)strcpy(tmp,ncp->nc_protofmly);
> - tmp = strchr(tmp, 0) + 1;
> - p->nc_proto = (char *)strcpy(tmp,ncp->nc_proto);
> - tmp = strchr(tmp, 0) + 1;
> - p->nc_device = (char *)strcpy(tmp,ncp->nc_device);
> + t = strchr(tmp, 0) + 1;
> + p->nc_protofmly = (char *)strcpy(t,ncp->nc_protofmly);
> + t = strchr(t, 0) + 1;
> + p->nc_proto = (char *)strcpy(t,ncp->nc_proto);
> + t = strchr(t, 0) + 1;
> + p->nc_device = (char *)strcpy(t,ncp->nc_device);
> p->nc_lookups = (char **)malloc((size_t)(p->nc_nlookups+1) * sizeof(char *));
> if (p->nc_lookups == NULL) {
> free(p->nc_netid);
Ok... I see why tmp original value needs to be maintained
to do the free()... but I'm wondering why the freeing
of p->nc_netid is needed... it appears to me it is part
of tmp string... so when tmp is freed won't p->nc_netid
be freed as well?

steved.


> @@ -714,8 +715,8 @@ struct netconfig *ncp;
> return(NULL);
> }
> for (i=0; i < p->nc_nlookups; i++) {
> - tmp = strchr(tmp, 0) + 1;
> - p->nc_lookups[i] = (char *)strcpy(tmp,ncp->nc_lookups[i]);
> + t = strchr(t, 0) + 1;
> + p->nc_lookups[i] = (char *)strcpy(t,ncp->nc_lookups[i]);
> }
> return(p);
> }
>