On Tue 27-02-18 00:12:57, Ilya Smith wrote: [...] > diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c > index 676774b9bb8d..1752fe5cb735 100644 > --- a/arch/x86/kernel/sys_x86_64.c > +++ b/arch/x86/kernel/sys_x86_64.c > @@ -17,6 +17,7 @@ > #include <linux/random.h> > #include <linux/uaccess.h> > #include <linux/elf.h> > +#include <linux/security.h> > > #include <asm/elf.h> > #include <asm/compat.h> > @@ -185,7 +186,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const > unsigned long addr0, > return addr; > > /* requested length too big for entire address space */ > - if (len > TASK_SIZE) > + if (len > TASK_SIZE - mmap_min_addr) > return -ENOMEM; > > /* No address checking. See comment at mmap_address_hint_valid() */ > @@ -210,7 +211,7 @@ arch_get_unmapped_area_topdown(struct file *filp, const > unsigned long addr0, > > info.flags = VM_UNMAPPED_AREA_TOPDOWN; > info.length = len; > - info.low_limit = PAGE_SIZE; > + info.low_limit = max(PAGE_SIZE, mmap_min_addr); > info.high_limit = get_mmap_base(0); > > /*
mmap_min_addr handling is a bit mess... As you say, we would return EPERM rather than ENOMEM which can be confusing but depleting the address space like that is quite unlikely on 64b unless I am missing. It is good to be in sync here with the generic implementation though, IMO. > diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c > index 155ecbac9e28..b6d0c317639e 100644 > --- a/arch/x86/mm/mmap.c > +++ b/arch/x86/mm/mmap.c > @@ -31,6 +31,7 @@ > #include <linux/sched/signal.h> > #include <linux/sched/mm.h> > #include <linux/compat.h> > +#include <linux/security.h> > #include <asm/elf.h> > > #include "physaddr.h" > @@ -220,6 +221,9 @@ bool mmap_address_hint_valid(unsigned long addr, unsigned > long len) > if (TASK_SIZE - len < addr) > return false; > > + if (addr < mmap_min_addr) > + return false; > + > return (addr > DEFAULT_MAP_WINDOW) == (addr + len > DEFAULT_MAP_WINDOW); But is this one necessary? We do sanitze hint address before going to get_unmapped_address AFAIR. -- Michal Hocko SUSE Labs
