On Wed, Sep 07, 2022 at 08:15:36AM +0300, Farber, Eliav wrote: > On 9/6/2022 5:10 PM, Andy Shevchenko wrote: > > On Tue, Sep 06, 2022 at 08:33:41AM +0000, Eliav Farber wrote: ... > > > + total_ch = ch_num * vm_num; > > > + in_config = devm_kcalloc(dev, total_ch + 1, > > > sizeof(*in_config), GFP_KERNEL); > > > > Strictly speaking this should be `size_add(size_mul(...) ...)` > > construction > > from overflow.h. > > > > total_ch = size_mul(ch_num, vm_num); > > in_config = devm_kcalloc(dev, size_add(total_ch, 1), > > sizeof(*in_config), GFP_KERNEL); > > > > Alternatively before doing all these, add a check > > > > if (array3_size(ch_num, vm_num, sizeof(*in_config)) < > > SIZE_MAX - sizeof(*in_config)) > > return -EOVERFLOW; > > > > But this is a bit monstrous. Seems like the above looks and feels better. > > > > Also for backporting purposes perhaps it's fine to do without using > > those macro > > helpers. > According to the driver code total_ch is a u32 variable while vm_num > and ch_num are both limited to a value of 31: > > #define VM_NUM_MSK GENMASK(20, 16) > #define VM_NUM_SFT 16 > #define CH_NUM_MSK GENMASK(31, 24) > #define CH_NUM_SFT 24 > > In addition the PVT Controller Series 3+ Specification mentions that > the actual maximum values are even smaller – 8 for vm_num and 16 for > ch_num. > Therefore we are very far from a scenario of an overflow. > Do you still think overflow protection in necessary? Like I said "Strictly..." Means it's up to you, but allocations are usually be protected against the overflows. -- With Best Regards, Andy Shevchenko
