Re: [PATCH] selftests/mm: fix memory leak in child_memcmp_fn

[Feng Jiang]

On 2023/4/4 15:31, David Hildenbrand wrote:
> On 04.04.23 05:12, Feng Jiang wrote:
> > The allocated memory should be freed on return.
> >
> > Signed-off-by: Feng Jiang <jiangfeng@xxxxxxxxxx>
> > Suggested-by: Ming Xie <xieming@xxxxxxxxxx>
> > ---
> >   tools/testing/selftests/mm/cow.c | 9 ++++++++-
> >   1 file changed, 8 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/testing/selftests/mm/cow.c 
> > b/tools/testing/selftests/mm/cow.c
> > index 0eb2e8180aa5..c0dd2dfca51b 100644
> > --- a/tools/testing/selftests/mm/cow.c
> > +++ b/tools/testing/selftests/mm/cow.c
> > @@ -162,6 +162,10 @@ static int child_memcmp_fn(char *mem, size_t size,
> >   {
> >       char *old = malloc(size);
> >       char buf;
> > +    int ret;
> > +
> > +    if (!old)
> > +        return -ENOMEM;
> >         /* Backup the original content. */
> >       memcpy(old, mem, size);
> > @@ -172,7 +176,10 @@ static int child_memcmp_fn(char *mem, size_t size,
> >           ;
> >         /* See if we still read the old values. */
> > -    return memcmp(old, mem, size);
> > +    ret = memcmp(old, mem, size);
> > +    free(old);
> > +
> > +    return ret;
> >   }
> >     static int child_vmsplice_memcmp_fn(char *mem, size_t size,
>
> NAK, the whole point of this function is that the child process will 
> exit immediately after executing this function, cleaning up 
> automatically.
Hi David, thanks very much for your review and I think you are right.

While the OS provides a cleanup mechanism to underwrite this, I think it 
makes sense for the application to ensure that its own logic is complete 
and correct.