Re: [PATCH] powerpc/powernv/npu: Allocate enough memory in pnv_try_setup_npu_table_group()

On Sat, Jan 12, 2019 at 08:44:26AM +0300, Dan Carpenter wrote:

On Sat, Jan 12, 2019 at 11:30:35AM +1100, Balbir Singh wrote:

quoted

On Wed, Jan 09, 2019 at 01:23:29PM +0300, Dan Carpenter wrote:

quoted

There is a typo so we accidentally allocate enough memory for a pointer
when we wanted to allocate enough for a struct.

Fixes: 0bd971676e68 ("powerpc/powernv/npu: Add compound IOMMU groups")
Signed-off-by: Dan Carpenter <redacted>
---
 arch/powerpc/platforms/powernv/npu-dma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/powernv/npu-dma.c b/arch/powerpc/platforms/powernv/npu-dma.c
index d7f742ed48ba..3f58c7dbd581 100644
--- a/arch/powerpc/platforms/powernv/npu-dma.c
+++ b/arch/powerpc/platforms/powernv/npu-dma.c

@@ -564,7 +564,7 @@ struct iommu_table_group *pnv_try_setup_npu_table_group(struct pnv_ioda_pe *pe)
 		}
 	} else {
 		/* Create a group for 1 GPU and attached NPUs for POWER8 */
-		pe->npucomp = kzalloc(sizeof(pe->npucomp), GFP_KERNEL);
+		pe->npucomp = kzalloc(sizeof(*pe->npucomp), GFP_KERNEL);

To avoid these in the future, I wonder if instead of sizeof(pe->npucomp), we insist on
sizeof structure

pe->npucomp = kzalloc(sizeof(struct npucomp), GFP_KERNEL);

The latest kernel fashion is sizeof(*ptr).  It can go wrong either way.
I don't have strong feelings about it.  These sorts of bugs don't last
long because they're caught in testing or with static analysis.

And it is easy to see someone forgot the * in "sizeof *ptr", and with
experience it will just automatically look wrong if it is forgotten; but
it isn't obvious at all if the wrong struct is used, which cannot happen
with the *ptr form, but happens frequently with the "sizeof(struct x)"
form.


Segher