From c38c8db7225465c8d124f38b24d3024decc26bbd Mon Sep 17 00:00:00 2001 From: Anil Keshavamurthy Date: Fri, 14 Jul 2006 00:23:57 -0700 Subject: [PATCH] [PATCH] ia64: race flushing icache in COW path There is a race condition that showed up in a threaded JIT environment. The situation is that a process with a JIT code page forks, so the page is marked read-only, then some threads are created in the child. One of the threads attempts to add a new code block to the JIT page, so a copy-on-write fault is taken, and the kernel allocates a new page, copies the data, installs the new pte, and then calls lazy_mmu_prot_update() to flush caches to make sure that the icache and dcache are in sync. Unfortunately, the other thread runs right after the new pte is installed, but before the caches have been flushed. It tries to execute some old JIT code that was already in this page, but it sees some garbage in the i-cache from the previous users of the new physical page. Fix: we must make the caches consistent before installing the pte. This is an ia64 only fix because lazy_mmu_prot_update() is a no-op on all other architectures. Signed-off-by: Anil Keshavamurthy Signed-off-by: Tony Luck Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/mm/memory.c b/mm/memory.c index dc0d82cf2a1c..de8bc85dc8f3 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -1549,9 +1549,9 @@ gotten: flush_cache_page(vma, address, pte_pfn(orig_pte)); entry = mk_pte(new_page, vma->vm_page_prot); entry = maybe_mkwrite(pte_mkdirty(entry), vma); + lazy_mmu_prot_update(entry); ptep_establish(vma, address, page_table, entry); update_mmu_cache(vma, address, entry); - lazy_mmu_prot_update(entry); lru_cache_add_active(new_page); page_add_new_anon_rmap(new_page, vma, address); -- 2.20.1