Re: [PATCH v1 2/2] async_tx: fix possible negative array indexing

[Rayagonda Kokatanur]

On Tue, Mar 17, 2020 at 11:06 PM Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
>
> On Mon, Mar 16, 2020 at 11:16 PM Rayagonda Kokatanur
> <rayagonda.kokatanur@xxxxxxxxxxxx> wrote:
> >
> > Fix possible negative array index read in __2data_recov_5() function.
> >
> > Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@xxxxxxxxxxxx>
> > ---
> >  crypto/async_tx/async_raid6_recov.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/crypto/async_tx/async_raid6_recov.c b/crypto/async_tx/async_raid6_recov.c
> > index 33f2a8f8c9f4..9cd016cb2d09 100644
> > --- a/crypto/async_tx/async_raid6_recov.c
> > +++ b/crypto/async_tx/async_raid6_recov.c
> > @@ -206,7 +206,7 @@ __2data_recov_5(int disks, size_t bytes, int faila, int failb,
> >                 good_srcs++;
> >         }
> >
> > -       if (good_srcs > 1)
> > +       if ((good_srcs > 1) || (good < 0))
> >                 return NULL;
>
> Read the code again, I don't see how this can happen.

This case can happen and it is reported by coverity tool.
In the for loop , the condition "if (blocks[i] == NULL)" true all the
time then variable 'good' will be -1.