From: Felix Fietkau <nbd@nbd.name> Date: Sun, 24 Jan 2016 01:03:51 +0100 Subject: [PATCH] MIPS: fix cache flushing for highmem pages Most cache flush ops were no-op for highmem pages. This led to nasty segfaults and (in the case of page_address(page) == NULL) kernel crashes. Fix this by always flushing highmem pages using kmap/kunmap_atomic around the actual cache flush. This might be a bit inefficient, but at least it's stable. Signed-off-by: Felix Fietkau <nbd@nbd.name> --- --- a/arch/mips/mm/cache.c +++ b/arch/mips/mm/cache.c @@ -111,6 +111,13 @@ void __flush_anon_page(struct page *page { unsigned long addr = (unsigned long) page_address(page); + if (PageHighMem(page)) { + addr = (unsigned long)kmap_atomic(page); + flush_data_cache_page(addr); + __kunmap_atomic((void *)addr); + return; + } + if (pages_do_alias(addr, vmaddr)) { if (page_mapped(page) && !Page_dcache_dirty(page)) { void *kaddr;