On 26/06/2020 16.29, Gustavo A. R. Silva wrote: > Hi Peter, > > Please, see my comments below... > > On Fri, Jun 26, 2020 at 10:30:37AM +0300, Peter Ujfalusi wrote: >> >> >> On 24/06/2020 20.12, Gustavo A. R. Silva wrote: >>> Hi Vinod, >>> >>> On 6/24/20 00:55, Vinod Koul wrote: >>>> On 19-06-20, 17:43, Gustavo A. R. Silva wrote: >>>>> Make use of the struct_size() helper instead of an open-coded version >>>>> in order to avoid any potential type mistakes. >>>>> >>>>> This code was detected with the help of Coccinelle and, audited and >>>>> fixed manually. >>>>> >>>>> Addresses-KSPP-ID: https://github.com/KSPP/linux/issues/83 >>>>> Signed-off-by: Gustavo A. R. Silva <gustavoars@xxxxxxxxxx> >>>>> --- >>>>> drivers/dma/ti/k3-udma.c | 4 ++-- >>>>> 1 file changed, 2 insertions(+), 2 deletions(-) >>>>> >>>>> diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c >>>>> index 0d5fb154b8e2..411c54b86ba8 100644 >>>>> --- a/drivers/dma/ti/k3-udma.c >>>>> +++ b/drivers/dma/ti/k3-udma.c >>>>> @@ -2209,7 +2209,7 @@ udma_prep_slave_sg_pkt(struct udma_chan *uc, struct scatterlist *sgl, >>>>> u32 ring_id; >>>>> unsigned int i; >>>>> >>>>> - d = kzalloc(sizeof(*d) + sglen * sizeof(d->hwdesc[0]), GFP_NOWAIT); >>>>> + d = kzalloc(struct_size(d, hwdesc, sglen), GFP_NOWAIT); >>>> >>>> struct_size() is a * b + c but here we need, a + b * c.. the trailing >>>> struct is N times here.. >>>> >>> >>> struct_size() works exactly as expected in this case. :) >>> Please, see: >>> >>> include/linux/overflow.h:314: >>> 314 #define struct_size(p, member, count) \ >>> 315 __ab_c_size(count, \ >>> 316 sizeof(*(p)->member) + __must_be_array((p)->member),\ >>> 317 sizeof(*(p))) >> >> True, struct_size is for this sort of things. >> >> Acked-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx> >> >> While looking it up in include/linux/overflow.h I have noticed your >> commit in linux-next, which adds flex_array_size() >> >> The example in the commit message contradicts with what the helper > > There is no contradiction here. > >> does imho. To be correct it should have been: >> >> struct something { >> size_t count; >> struct foo items[]; >> }; >> >> - struct something *instance; >> + struct something instance; >> >> - instance = kmalloc(struct_size(instance, items, count), GFP_KERNEL); >> + instance.items = kmalloc(struct_size(instance, items, count), GFP_KERNEL); >> instance->count = count; >> memcpy(instance->items, src, flex_array_size(instance, items, instance->count)); >> > > This is all wrong. Please, double check how struct_size() works. Yes, I got it mixed up, I know how struct_size works... For some reason I just overlooked it's use in the kmalloc(). > > Thanks > -- > Gustavo > >>>>> if (!d) >>>>> return NULL; >>>>> >>>>> @@ -2525,7 +2525,7 @@ udma_prep_dma_cyclic_pkt(struct udma_chan *uc, dma_addr_t buf_addr, >>>>> if (period_len >= SZ_4M) >>>>> return NULL; >>>>> >>>>> - d = kzalloc(sizeof(*d) + periods * sizeof(d->hwdesc[0]), GFP_NOWAIT); >>>>> + d = kzalloc(struct_size(d, hwdesc, periods), GFP_NOWAIT); >>>>> if (!d) >>>>> return NULL; >>>>> >>>>> -- >>>>> 2.27.0 >>>> >> >> - Péter >> >> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki >> - Péter Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
