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SubjectRe: [PATCH] zram: fix possible use after free in zcomp_create()
On (09/07/15 13:53), Luis Henriques wrote:
> > On (09/07/15 11:33), Luis Henriques wrote:
> > > zcomp_create() verifies the success of zcomp_strm_{multi,siggle}_create()
> > > through comp->stream, which can potentially be pointing to memory that was
> > > freed if these functions returned an error.
> > >
> >
> > good catch.
> >
> > we probably better start checking the zcomp_strm_multi_create()/
> > zcomp_strm_single_create() status in zcomp_create(); that's much
> > more obvious and that's why we return it in the first place.
> >
> > what do you think?
> >
>
> Yep, that's probably a better solution.
>
> Acked-by: Luis Henriques <luis.henriques@canonical.com>
>

Oh, thanks. I don't mind if you will re-submit it; I just did minor
changes to our fix. Or I can handle it. I'm OK with either way. Btw,
did you hit that problem or you reviewed the code?

-ss

> Cheers,
> --
> Luís
>
> > ---
> >
> > drivers/block/zram/zcomp.c | 7 ++++---
> > 1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/block/zram/zcomp.c b/drivers/block/zram/zcomp.c
> > index 3456d5a..16bbc8c 100644
> > --- a/drivers/block/zram/zcomp.c
> > +++ b/drivers/block/zram/zcomp.c
> > @@ -360,6 +360,7 @@ struct zcomp *zcomp_create(const char *compress, int max_strm)
> > {
> > struct zcomp *comp;
> > struct zcomp_backend *backend;
> > + int ret;
> >
> > backend = find_backend(compress);
> > if (!backend)
> > @@ -371,10 +372,10 @@ struct zcomp *zcomp_create(const char *compress, int max_strm)
> >
> > comp->backend = backend;
> > if (max_strm > 1)
> > - zcomp_strm_multi_create(comp, max_strm);
> > + ret = zcomp_strm_multi_create(comp, max_strm);
> > else
> > - zcomp_strm_single_create(comp);
> > - if (!comp->stream) {
> > + ret = zcomp_strm_single_create(comp);
> > + if (ret != 0) {
> > kfree(comp);
> > return ERR_PTR(-ENOMEM);
> > }
> >
>


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