From: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx> Reviewed-by: Khalid Aziz <khalid.aziz@xxxxxxxxxx> Reviewed-by: Vincenzo Frascino <vincenzo.frascino@xxxxxxx> Reviewed-by: Kees Cook <keescook@xxxxxxxxxxxx> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxx> Cc: Eric Auger <eric.auger@xxxxxxxxxx> Cc: Felix Kuehling <Felix.Kuehling@xxxxxxx> Cc: Jens Wiklander <jens.wiklander@xxxxxxxxxx> Cc: Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx> Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx> Cc: Will Deacon <will@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/gup.c | 4 ++++ 1 file changed, 4 insertions(+) --- a/mm/gup.c~mm-untag-user-pointers-in-mm-gupc +++ a/mm/gup.c @@ -788,6 +788,8 @@ static long __get_user_pages(struct task 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 struct vm_area_struct *vma; vm_fault_t ret, major = 0; + address = untagged_addr(address); + if (unlocked) fault_flags |= FAULT_FLAG_ALLOW_RETRY; _
