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. BR, Jani. [1] https://cgit.freedesktop.org/drm/drm-tip > > Regards, > Len -- Jani Nikula, Intel Open Source Graphics Center
