From f9652594195fca8c3d8b8ee392ad0ff9f701bb20 Mon Sep 17 00:00:00 2001 From: Andrey Konovalov Date: Wed, 25 Sep 2019 16:48:34 -0700 Subject: [PATCH] mm: untag user pointers in mm/gup.c This patch is a part of a series that extends kernel ABI to allow to pass tagged user pointers (with the top byte set to something else other than 0x00) as syscall arguments. mm/gup.c provides a kernel interface that accepts user addresses and manipulates user pages directly (for example get_user_pages, that is used by the futex syscall). Since a user can provided tagged addresses, we need to handle this case. Add untagging to gup.c functions that use user addresses for vma lookups. Link: http://lkml.kernel.org/r/4731bddba3c938658c10ff4ed55cc01c60f4c8f8.1563904656.git.andreyknvl@google.com Signed-off-by: Andrey Konovalov Reviewed-by: Khalid Aziz Reviewed-by: Vincenzo Frascino Reviewed-by: Kees Cook Reviewed-by: Catalin Marinas Cc: Al Viro Cc: Dave Hansen Cc: Eric Auger Cc: Felix Kuehling Cc: Jens Wiklander Cc: Mauro Carvalho Chehab Cc: Mike Rapoport Cc: Will Deacon Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/gup.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/gup.c b/mm/gup.c index 60c3915c8ee6..23a9f9c9d377 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -788,6 +788,8 @@ static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm, if (!nr_pages) return 0; + start = untagged_addr(start); + VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET)); /* @@ -950,6 +952,8 @@ int fixup_user_fault(struct task_struct *tsk, struct mm_struct *mm, struct vm_area_struct *vma; vm_fault_t ret, major = 0; + address = untagged_addr(address); + if (unlocked) fault_flags |= FAULT_FLAG_ALLOW_RETRY; -- 2.30.2