On Fri, Dec 18, 2015 at 07:33:36AM +0100, Julia Lawall wrote:
>
>
> On Mon, 14 Dec 2015, Nicholas Mc Guire wrote:
>
> > On Thu, Dec 10, 2015 at 11:13:38AM -0500, Mike Marciniszyn wrote:
> > > From: Easwar Hariharan <easwar.hariharan@xxxxxxxxx>
> > >
> > > A code inspection pointed out that kmalloc_array may return NULL and
> > > memset doesn't check the input pointer for NULL, resulting in a possible
> > > NULL dereference. This patch fixes this.
> > >
> > > Reviewed-by: Mike Marciniszyn <mike.marciniszyn@xxxxxxxxx>
> > > Signed-off-by: Easwar Hariharan <easwar.hariharan@xxxxxxxxx>
> > > ---
> > > drivers/staging/rdma/hfi1/chip.c | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/staging/rdma/hfi1/chip.c b/drivers/staging/rdma/hfi1/chip.c
> > > index dc69159..49d49b2 100644
> > > --- a/drivers/staging/rdma/hfi1/chip.c
> > > +++ b/drivers/staging/rdma/hfi1/chip.c
> > > @@ -10129,6 +10129,8 @@ static void init_qos(struct hfi1_devdata *dd, u32 first_ctxt)
> > > if (num_vls * qpns_per_vl > dd->chip_rcv_contexts)
> > > goto bail;
> > > rsmmap = kmalloc_array(NUM_MAP_REGS, sizeof(u64), GFP_KERNEL);
> > > + if (!rsmmap)
> > > + goto bail;
> > > memset(rsmmap, rxcontext, NUM_MAP_REGS * sizeof(u64));
> > > /* init the local copy of the table */
> > > for (i = 0, ctxt = first_ctxt; i < num_vls; i++) {
> > >
> > > --
> >
> > Based on this report a generalization of unchecked use turned up one more
> > case in the current kernel (patch sent). Probably the when block needs
> > some cleanup, but findings like this definitely are a case for coccinelle
> > scanners.
> >
> > <snip>
> > /// check for missing NULL check before use
> > //
> > // missing check in:
> > // ./drivers/staging/rdma/hfi1/chip.c:10131 unchecked allocation
> > // in -next-20151214
> > // reported-by Mike Marciniszyn <mike.marciniszyn@xxxxxxxxx>
> > //
> > // after generalization this also found:
> > // ./drivers/clk/shmobile/clk-div6.c:197 unchecked allocation
> >
> > virtual context
> > virtual org
> > virtual report
> >
> > @badmemset@
> > expression mem;
> > position p;
> > statement S;
> > @@
> >
> > <+...
> > *mem = kmalloc_array@p(...);
> > ... when != if (!mem || ...) S
> > when != if (... && !mem) S
> > when != if (mem == NULL || ...) S
> > when != if (... && mem == NULL) S
> > when != if (unlikely(mem == NULL)) S
> > when != if (unlikely(!mem)) S
> > when != if (likely(!mem)) S
> > when != if (likely(mem == NULL)) S
> > return;
> > ...+>
> >
> > @script:python@
> > p << badmemset.p;
> > @@
> >
> > print "%s:%s unchecked allocation" % (p[0].file,p[0].line)
> >
> > <snip>
>
> How about the following? I got two hits with this, in
> drivers/clk/shmobile/clk-div6.c and drivers/staging/rdma/hfi1/chip.c.
>
> @@
> expression mem;
> identifier f;
> @@
>
> *mem = kmalloc_array(...);
> ... when != mem == NULL
> when != mem != NULL
> (
works perfectly for this case - thanks
I actually initially used the "template" from api/alloc/kzalloc-simple.cocci
but that did not catch all cases for the kmalloc_array scanner.
Poping your proposal into kzalloc-simple.cocci seems to be finding quite
a few additional cases will review them to see if there are any false
positives - but a first scan did show that most of the reported cases
seem to be valid.
thx!
hofrat
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