Hugh Dickins 1be7107fbe mm: larger stack guard gap, between vmas ... Stack guard page is a useful feature to reduce a risk of stack smashing into a different mapping. We have been using a single page gap which is sufficient to prevent having stack adjacent to a different mapping. But this seems to be insufficient in the light of the stack usage in userspace. E.g. glibc uses as large as 64kB alloca() in many commonly used functions. Others use constructs liks gid_t buffer[NGROUPS_MAX] which is 256kB or stack strings with MAX_ARG_STRLEN. This will become especially dangerous for suid binaries and the default no limit for the stack size limit because those applications can be tricked to consume a large portion of the stack and a single glibc call could jump over the guard page. These attacks are not theoretical, unfortunatelly. Make those attacks less probable by increasing the stack guard gap to 1MB (on systems with 4k pages; but make it depend on the page size because systems with larger base pages might cap stack allocations in the PAGE_SIZE units) which should cover larger alloca() and VLA stack allocations. It is obviously not a full fix because the problem is somehow inherent, but it should reduce attack space a lot. One could argue that the gap size should be configurable from userspace, but that can be done later when somebody finds that the new 1MB is wrong for some special case applications. For now, add a kernel command line option (stack_guard_gap) to specify the stack gap size (in page units). Implementation wise, first delete all the old code for stack guard page: because although we could get away with accounting one extra page in a stack vma, accounting a larger gap can break userspace - case in point, a program run with "ulimit -S -v 20000" failed when the 1MB gap was counted for RLIMIT_AS; similar problems could come with RLIMIT_MLOCK and strict non-overcommit mode. Instead of keeping gap inside the stack vma, maintain the stack guard gap as a gap between vmas: using vm_start_gap() in place of vm_start (or vm_end_gap() in place of vm_end if VM_GROWSUP) in just those few places which need to respect the gap - mainly arch_get_unmapped_area(), and and the vma tree's subtree_gap support for that. Original-patch-by: Oleg Nesterov <oleg@redhat.com> Original-patch-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Michal Hocko <mhocko@suse.com> Tested-by: Helge Deller <deller@gmx.de> # parisc Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		2017-06-19 21:50:20 +08:00
..
kasan	Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2017-05-10 10:30:46 -07:00
backing-dev.c	bdi: Drop 'parent' argument from bdi_register[_va]()	2017-04-20 12:09:55 -06:00
balloon_compaction.c	mm: balloon: use general non-lru movable page feature	2016-07-26 16:19:19 -07:00
bootmem.c	mm/bootmem.c: cosmetic improvement of code readability	2017-02-22 16:41:29 -08:00
cleancache.c	cleancache: constify cleancache_ops structure	2016-01-27 09:09:57 -05:00
cma_debug.c	cma: Store a name in the cma structure	2017-04-18 20:41:12 +02:00
cma.c	cma: Introduce cma_for_each_area	2017-04-18 20:41:12 +02:00
cma.h	cma: Store a name in the cma structure	2017-04-18 20:41:12 +02:00
compaction.c	mm, compaction: finish whole pageblock to reduce fragmentation	2017-05-08 17:15:10 -07:00
debug_page_ref.c	mm/page_ref: add tracepoint to track down page reference manipulation	2016-03-17 15:09:34 -07:00
debug.c	mm, debug: print raw struct page data in __dump_page()	2016-12-12 18:55:08 -08:00
dmapool.c	lib/vsprintf.c: remove %Z support	2017-02-27 18:43:47 -08:00
early_ioremap.c	mm/early_ioremap: use offset_in_page macro	2015-11-05 19:34:48 -08:00
fadvise.c	mm: fadvise: avoid expensive remote LRU cache draining after FADV_DONTNEED	2016-12-20 09:48:46 -08:00
failslab.c	mm: fault-inject take over bootstrap kmem_cache check	2016-03-15 16:55:16 -07:00
filemap.c	Merge branch 'work.iov_iter' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2017-05-09 09:01:21 -07:00
frame_vector.c	treewide: use kv[mz]alloc* rather than opencoded variants	2017-05-08 17:15:13 -07:00
frontswap.c	mm, frontswap: convert frontswap_enabled to static key	2016-07-26 16:19:19 -07:00
gup.c	mm: larger stack guard gap, between vmas	2017-06-19 21:50:20 +08:00
highmem.c	mm/highmem: make nr_free_highpages() handles all highmem zones by itself	2016-05-19 19:12:14 -07:00
huge_memory.c	mm: numa: avoid waiting on freed migrated pages	2017-06-17 06:37:05 +09:00
hugetlb_cgroup.c	mm, hugetlb_cgroup: round limit_in_bytes down to hugepage size	2016-05-20 17:58:30 -07:00
hugetlb.c	mm/hugetlb: report -EHWPOISON not -EFAULT when FOLL_HWPOISON is specified	2017-06-02 15:07:38 -07:00
hwpoison-inject.c	mm: hwpoison: call shake_page() unconditionally	2017-05-03 15:52:12 -07:00
init-mm.c	mm: Add a user_ns owner to mm_struct and fix ptrace permission checks	2016-11-22 11:49:48 -06:00
internal.h	mm, compaction: finish whole pageblock to reduce fragmentation	2017-05-08 17:15:10 -07:00
interval_tree.c
Kconfig	mm: remove AVR32 arch special handling in mm/Kconfig	2017-05-01 09:36:31 +02:00
Kconfig.debug	mm: enable page poisoning early at boot	2017-05-03 15:52:10 -07:00
khugepaged.c	mm, thp: copying user pages must schedule on collapse	2017-05-12 15:57:16 -07:00
kmemcheck.c	mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU	2017-04-18 11:42:36 -07:00
kmemleak-test.c	mm: convert printk(KERN_<LEVEL> to pr_<level>	2016-03-17 15:09:34 -07:00
kmemleak.c	mm: fix section name for .data..ro_after_init	2017-03-31 17:13:30 -07:00
ksm.c	ksm: prevent crash after write_protect_page fails	2017-06-02 15:07:37 -07:00
list_lru.c	mm/list_lru.c: avoid error-path NULL pointer deref	2016-10-27 18:43:42 -07:00
maccess.c	x86: remove more uaccess_32.h complexity	2016-05-22 17:21:27 -07:00
madvise.c	mm/madvise: move up the behavior parameter validation	2017-05-03 15:52:11 -07:00
Makefile	mm: add arch-independent testcases for RODATA	2017-02-27 18:43:48 -08:00
memblock.c	mm: consider memblock reservations for deferred memory initialization sizing	2017-06-02 15:07:38 -07:00
memcontrol.c	hwpoison, memcg: forcibly uncharge LRU pages	2017-05-12 15:57:15 -07:00
memory_hotplug.c	mm, vmscan: prevent kswapd sleeping prematurely due to mismatched classzone_idx	2017-05-03 15:52:09 -07:00
memory-failure.c	mm/memory-failure.c: use compound_head() flags for huge pages	2017-06-17 06:37:05 +09:00
memory.c	mm: larger stack guard gap, between vmas	2017-06-19 21:50:20 +08:00
mempolicy.c	mm/mempolicy.c: fix error handling in set_mempolicy and mbind.	2017-04-08 10:57:55 -07:00
mempool.c	Revert "mm, mempool: only set __GFP_NOMEMALLOC if there are free elements"	2016-07-28 16:07:41 -07:00
memtest.c
migrate.c	mm: make rmap_one boolean function	2017-05-03 15:52:10 -07:00
mincore.c	mm: remove shmem_mapping() shmem_zero_setup() duplicates	2017-02-24 17:46:56 -08:00
mlock.c	mlock: fix mlock count can not decrease in race condition	2017-06-02 15:07:38 -07:00
mm_init.c	mm: convert printk(KERN_<LEVEL> to pr_<level>	2016-03-17 15:09:34 -07:00
mmap.c	mm: larger stack guard gap, between vmas	2017-06-19 21:50:20 +08:00
mmu_context.c	sched/headers: Prepare to move the task_lock()/unlock() APIs to <linux/sched/task.h>	2017-03-02 08:42:38 +01:00
mmu_notifier.c	mm: Use static initialization for "srcu"	2017-04-18 11:38:22 -07:00
mmzone.c	mm/mmzone.c: swap likely to unlikely as code logic is different for next_zones_zonelist()	2017-02-22 16:41:29 -08:00
mprotect.c	mm: convert generic code to 5-level paging	2017-03-09 11:48:47 -08:00
mremap.c	mm: convert generic code to 5-level paging	2017-03-09 11:48:47 -08:00
msync.c	mm/msync: use offset_in_page macro	2015-11-05 19:34:48 -08:00
nobootmem.c	mm: kmemleak: avoid using __va() on addresses that don't have a lowmem mapping	2016-10-11 15:06:33 -07:00
nommu.c	mm, vmalloc: use __GFP_HIGHMEM implicitly	2017-05-08 17:15:13 -07:00
oom_kill.c	oom: improve oom disable handling	2017-05-03 15:52:10 -07:00
page_alloc.c	mm: consider memblock reservations for deferred memory initialization sizing	2017-06-02 15:07:38 -07:00
page_counter.c	mm: page_counter: let page_counter_try_charge() return bool	2015-11-05 19:34:48 -08:00
page_ext.c	mm: enable page poisoning early at boot	2017-05-03 15:52:10 -07:00
page_idle.c	mm: make rmap_one boolean function	2017-05-03 15:52:10 -07:00
page_io.c	writeback: add wbc_to_write_flags()	2016-11-02 10:24:03 -06:00
page_isolation.c	mm, page_alloc: count movable pages when stealing from pageblock	2017-05-08 17:15:10 -07:00
page_owner.c	mm/page_owner: don't define fields on struct page_ext by hard-coding	2016-10-07 18:46:27 -07:00
page_poison.c	mm: enable page poisoning early at boot	2017-05-03 15:52:10 -07:00
page_vma_mapped.c	mm: fix page_vma_mapped_walk() for ksm pages	2017-04-08 00:47:48 -07:00
page-writeback.c	Add GETFSMAP support; some performance improvements for very large	2017-05-08 11:30:05 -07:00
pagewalk.c	mm: convert generic code to 5-level paging	2017-03-09 11:48:47 -08:00
percpu-km.c	mm: percpu: use pr_fmt to prefix output	2016-03-17 15:09:34 -07:00
percpu-vm.c	percpu: remove unused chunk_alloc parameter from pcpu_get_pages()	2017-03-06 15:56:55 -05:00
percpu.c	Merge branch 'sched/core' into locking/core	2017-04-04 11:31:12 +02:00
pgtable-generic.c	mm: convert generic code to 5-level paging	2017-03-09 11:48:47 -08:00
process_vm_access.c	sched/headers: Prepare for new header dependencies before moving code to <linux/sched/mm.h>	2017-03-02 08:42:28 +01:00
quicklist.c	fix Christoph's email addresses	2016-03-17 15:09:34 -07:00
readahead.c	mm: don't cap request size based on read-ahead setting	2016-12-12 18:55:08 -08:00
rmap.c	Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2017-05-10 10:30:46 -07:00
rodata_test.c	mm: remove rodata_test_data export, add pr_fmt	2017-05-03 15:52:09 -07:00
shmem.c	Merge branch 'rebased-statx' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs	2017-03-03 11:38:56 -08:00
slab_common.c	mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU	2017-04-18 11:42:36 -07:00
slab.c	Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip	2017-05-10 10:30:46 -07:00
slab.h	mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU	2017-04-18 11:42:36 -07:00
slob.c	mm: Rename SLAB_DESTROY_BY_RCU to SLAB_TYPESAFE_BY_RCU	2017-04-18 11:42:36 -07:00
slub.c	slub/memcg: cure the brainless abuse of sysfs attributes	2017-06-02 15:07:37 -07:00
sparse-vmemmap.c	mm: convert generic code to 5-level paging	2017-03-09 11:48:47 -08:00
sparse.c	mm/sparse: refine usemap_size() a little	2017-05-03 15:52:09 -07:00
swap_cgroup.c	swap: cond_resched in swap_cgroup_prepare()	2017-06-17 06:37:05 +09:00
swap_slots.c	mm, swap: use kvzalloc to allocate some swap data structures	2017-05-08 17:15:13 -07:00
swap_state.c	mm, swap: use kvzalloc to allocate some swap data structures	2017-05-08 17:15:13 -07:00
swap.c	mm: move MADV_FREE pages into LRU_INACTIVE_FILE list	2017-05-03 15:52:08 -07:00
swapfile.c	mm, swap: use kvzalloc to allocate some swap data structures	2017-05-08 17:15:13 -07:00
truncate.c	mm: fix data corruption due to stale mmap reads	2017-05-12 15:57:15 -07:00
usercopy.c	mm/usercopy: Drop extra is_vmalloc_or_module() check	2017-04-05 12:30:18 -07:00
userfaultfd.c	mm: convert generic code to 5-level paging	2017-03-09 11:48:47 -08:00
util.c	mm: clarify why we want kmalloc before falling backto vmallock	2017-06-02 15:07:37 -07:00
vmacache.c	sched/headers: Prepare to move 'init_task' and 'init_thread_union' from <linux/sched.h> to <linux/sched/task.h>	2017-03-02 08:42:38 +01:00
vmalloc.c	mm, vmalloc: fix vmalloc users tracking properly	2017-05-12 15:57:15 -07:00
vmpressure.c	mm: correct the comment when reclaimed pages exceed the scanned pages	2017-06-17 06:37:05 +09:00
vmscan.c	mm: vmscan: scan until it finds eligible pages	2017-05-12 15:57:16 -07:00
vmstat.c	mm, vmstat: Remove spurious WARN() during zoneinfo print	2017-05-12 15:57:15 -07:00
workingset.c	mm: memcontrol: use node page state naming scheme for memcg	2017-05-03 15:52:11 -07:00
z3fold.c	z3fold: fix page locking in z3fold_alloc()	2017-04-13 18:24:20 -07:00
zbud.c	mm/zbud.c: use list_last_entry() instead of list_tail_entry()	2016-01-15 11:40:52 -08:00
zpool.c	mm: zsmalloc: constify struct zs_pool name	2015-11-06 17:50:42 -08:00
zsmalloc.c	zsmalloc: expand class bit	2017-04-13 18:24:21 -07:00
zswap.c	zswap: don't param_set_charp while holding spinlock	2017-02-27 18:43:45 -08:00