From dc4fac84f8e66b147921ebdc385e767d5def7422 Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Tue, 10 May 2016 14:10:29 -0700 Subject: [PATCH] x86/mm: Switch from TASK_SIZE to TASK_SIZE_MAX in the page fault code x86's page fault handlers had two TASK_SIZE uses that should have been TASK_SIZE_MAX. I don't think that either one had a visible effect, but this makes the code clearer and should save a few bytes of text. (And I eventually want to eradicate TASK_SIZE. This will help.) Reported-by: Cyrill Gorcunov Signed-off-by: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: Dmitry Safonov <0x7f454c46@gmail.com> Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Pavel Emelyanov Cc: Peter Zijlstra Cc: Ruslan Kabatsayev Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1242fb23b0d05c3069dbf5758ac55d26bc114bef.1462914565.git.luto@kernel.org Signed-off-by: Ingo Molnar --- arch/x86/mm/fault.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c index 5ce1ed02f7e8..7d1fa7cd2374 100644 --- a/arch/x86/mm/fault.c +++ b/arch/x86/mm/fault.c @@ -292,7 +292,7 @@ void vmalloc_sync_all(void) return; for (address = VMALLOC_START & PMD_MASK; - address >= TASK_SIZE && address < FIXADDR_TOP; + address >= TASK_SIZE_MAX && address < FIXADDR_TOP; address += PMD_SIZE) { struct page *page; @@ -854,8 +854,13 @@ __bad_area_nosemaphore(struct pt_regs *regs, unsigned long error_code, return; } #endif - /* Kernel addresses are always protection faults: */ - if (address >= TASK_SIZE) + + /* + * To avoid leaking information about the kernel page table + * layout, pretend that user-mode accesses to kernel addresses + * are always protection faults. + */ + if (address >= TASK_SIZE_MAX) error_code |= PF_PROT; if (likely(show_unhandled_signals)) -- 2.20.1