On Wed, Jun 13, 2018 at 10:58:37AM +0200, Marek Szyprowski wrote: > cma_alloc() function has gfp mask parameter, so users expect that it > honors typical memory allocation related flags. The most imporant from > the security point of view is handling of __GFP_ZERO flag, because memory > allocated by this function usually can be directly remapped to userspace > by device drivers as a part of multimedia processing and ignoring this > flag might lead to leaking some kernel structures to userspace. > Some callers of this function (for example arm64 dma-iommu glue code) > already assumed that the allocated buffers are cleared when this flag > is set. To avoid such issues, add simple code for clearing newly > allocated buffer when __GFP_ZERO flag is set. Callers will be then > updated to skip implicit clearing or adjust passed gfp flags.
dma mapping implementations need to zero all memory returned anyway (even if a few implementation don't do that yet). I'd rather keep the zeroing in the common callers.
