From: Ard Biesheuvel <[email protected]> Allow permission changes on huge vmappings in cases where no splitting is needed (i.e., the region is aligned sufficiently), or when the system has support for splitting live mappings.
Signed-off-by: Ard Biesheuvel <[email protected]> --- arch/arm64/mm/pageattr.c | 13 ++++++++++--- 1 file changed, 10 insertions(+), 3 deletions(-) diff --git a/arch/arm64/mm/pageattr.c b/arch/arm64/mm/pageattr.c index bbe98ac9ad8c..20ff9cb273c1 100644 --- a/arch/arm64/mm/pageattr.c +++ b/arch/arm64/mm/pageattr.c @@ -169,8 +169,6 @@ static int change_memory_common(unsigned long addr, int numpages, * we are operating on does not result in such splitting. * * Let's restrict ourselves to mappings created by vmalloc (or vmap). - * Disallow VM_ALLOW_HUGE_VMAP mappings to guarantee that only page - * mappings are updated and splitting is never needed. * * So check whether the [addr, addr + size) interval is entirely * covered by precisely one VM area that has the VM_ALLOC flag set. @@ -179,7 +177,16 @@ static int change_memory_common(unsigned long addr, int numpages, if (!area || ((unsigned long)kasan_reset_tag((void *)end) > (unsigned long)kasan_reset_tag(area->addr) + area->size) || - ((area->flags & (VM_ALLOC | VM_ALLOW_HUGE_VMAP)) != VM_ALLOC)) + !(area->flags & VM_ALLOC)) + return -EINVAL; + + /* + * Disallow VM_ALLOW_HUGE_VMAP mappings unless the region is PMD + * aligned, or splitting live huge mappings is supported. + */ + if ((area->flags & VM_ALLOW_HUGE_VMAP) && + ((start % PMD_SIZE) || (size % PMD_SIZE)) && + WARN_ON_ONCE(!system_supports_bbml2_noabort())) return -EINVAL; if (!numpages) -- 2.55.0.860.g4b6b3295ed-goog
