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SubjectRe: [PATCH] kobject_set_name_vargs memory leak
On (06/26/09 16:00), Eric W. Biederman wrote:
> >> > Fix memory leak when kobject_set_name_vargs returns -ENOMEM.
> >> >
> >> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@mail.by>
> >> > ---
> >> > diff --git a/lib/kobject.c b/lib/kobject.c
> >> > index b512b74..922cd8c 100644
> >> > --- a/lib/kobject.c
> >> > +++ b/lib/kobject.c
> >> > @@ -222,8 +222,10 @@ int kobject_set_name_vargs(struct kobject *kobj, const char *fmt,
> >> > return 0;
> >> >
> >> > kobj->name = kvasprintf(GFP_KERNEL, fmt, vargs);
> >> > - if (!kobj->name)
> >> > + if (!kobj->name) {
> >> > + kfree(old_name);
> >> > return -ENOMEM;
> >> > + }
> >>
> >> We've been through this before (search lkml archives). If kvasprintf
> >> fails, then we don't want to free old_name, as the caller might want to
> >> do something with it.
> >>
> > Hello Greg,
> >
> > int kobject_set_name_vargs.... {
> > const char *old_name = kobj->name;
> >
> > old_name is local variable.
> >
> > In the following lines we overwrite kobject->name.
> >
> > kobj->name = kvasprintf(GFP_KERNEL, fmt, vargs);
> > if (!kobj->name)
> > return -ENOMEM;
> >
> > It's not clear to me how we can do anything (including kfree) with old_name after 'return -ENOMEM'.
>
> My feel is that if we fail we should restore kobject->name to old_name.
>
> That should also prevent the leak without getting us into trouble elsewhere.
>
> Eric
>
Or work with 'new_name' and overwrite kobject->name only 'if(new_name)'.
I thought about restoring. ( Blue or Red Pill? :) )

diff --git a/lib/kobject.c b/lib/kobject.c
index b512b74..d6b1502 100644
--- a/lib/kobject.c
+++ b/lib/kobject.c
@@ -222,8 +222,10 @@ int kobject_set_name_vargs(struct kobject *kobj, const char *fmt,
return 0;

kobj->name = kvasprintf(GFP_KERNEL, fmt, vargs);
- if (!kobj->name)
+ if (!kobj->name) {
+ kobj->name = old_name;
return -ENOMEM;
+ }

/* ewww... some of these buggers have '/' in the name ... */
while ((s = strchr(kobj->name, '/')))


Sergey


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