On Wed, Oct 13, 2021 at 02:24:05PM +0300, Jani Nikula wrote: > On Mon, 11 Oct 2021, Len Baker <len.baker@xxxxxxx> wrote: > > Hi, > > > > On Sun, Oct 03, 2021 at 12:42:58PM +0200, Len Baker wrote: > >> As noted in the "Deprecated Interfaces, Language Features, Attributes, > >> and Conventions" documentation [1], size calculations (especially > >> multiplication) should not be performed in memory allocator (or similar) > >> function arguments due to the risk of them overflowing. This could lead > >> to values wrapping around and a smaller allocation being made than the > >> caller was expecting. Using those allocations could lead to linear > >> overflows of heap memory and other misbehaviors. > >> > >> In this case these are not actually dynamic sizes: all the operands > >> involved in the calculation are constant values. However it is better to > >> refactor them anyway, just to keep the open-coded math idiom out of > >> code. > >> > >> So, add at the end of the struct i915_syncmap a union with two flexible > >> array members (these arrays share the same memory layout). This is > >> possible using the new DECLARE_FLEX_ARRAY macro. And then, use the > >> struct_size() helper to do the arithmetic instead of the argument > >> "size + count * size" in the kmalloc and kzalloc() functions. > >> > >> Also, take the opportunity to refactor the __sync_seqno and __sync_child > >> making them more readable. > >> > >> This code was detected with the help of Coccinelle and audited and fixed > >> manually. > >> > >> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments > >> > >> Signed-off-by: Len Baker <len.baker@xxxxxxx> > >> --- > >> drivers/gpu/drm/i915/i915_syncmap.c | 12 ++++++++---- > >> 1 file changed, 8 insertions(+), 4 deletions(-) > > > > I received a mail telling that this patch doesn't build: > > > > == Series Details == > > > > Series: drm/i915: Prefer struct_size over open coded arithmetic > > URL : https://patchwork.freedesktop.org/series/95408/ > > State : failure > > > > But it builds without error against linux-next (tag next-20211001). Against > > which tree and branch do I need to build? > > drm-tip [1]. It's a sort of linux-next for graphics. I think there are > still some branches that don't feed to linux-next. Yeah we need to get gt-next in linux-next asap. Joonas promised to send out his patch to make that happen in dim. -Daniel > > BR, > Jani. > > > [1] https://cgit.freedesktop.org/drm/drm-tip > > > > > > Regards, > > Len > > -- > Jani Nikula, Intel Open Source Graphics Center -- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch
