1 files changed, 30 insertions, 0 deletions
diff --git a/target/linux/generic/pending-4.14/100-MIPS-fix-cache-flushing-for-highmem-pages.patch b/target/linux/generic/pending-4.14/100-MIPS-fix-cache-flushing-for-highmem-pages.patch
new file mode 100644
index 0000000000..b1c65f7cd8
--- /dev/null
+++ b/target/linux/generic/pending-4.14/100-MIPS-fix-cache-flushing-for-highmem-pages.patch
@@ -0,0 +1,30 @@
+From: Felix Fietkau <nbd@nbd.name>
+Subject: 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
+@@ -116,6 +116,13 @@ 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_mapcount(page) && !Page_dcache_dirty(page)) {
+ 			void *kaddr;