linux-hardened/mm
Rik van Riel d2cd9ede6e mm,fork: introduce MADV_WIPEONFORK
Introduce MADV_WIPEONFORK semantics, which result in a VMA being empty
in the child process after fork.  This differs from MADV_DONTFORK in one
important way.

If a child process accesses memory that was MADV_WIPEONFORK, it will get
zeroes.  The address ranges are still valid, they are just empty.

If a child process accesses memory that was MADV_DONTFORK, it will get a
segmentation fault, since those address ranges are no longer valid in
the child after fork.

Since MADV_DONTFORK also seems to be used to allow very large programs
to fork in systems with strict memory overcommit restrictions, changing
the semantics of MADV_DONTFORK might break existing programs.

MADV_WIPEONFORK only works on private, anonymous VMAs.

The use case is libraries that store or cache information, and want to
know that they need to regenerate it in the child process after fork.

Examples of this would be:
 - systemd/pulseaudio API checks (fail after fork) (replacing a getpid
   check, which is too slow without a PID cache)
 - PKCS#11 API reinitialization check (mandated by specification)
 - glibc's upcoming PRNG (reseed after fork)
 - OpenSSL PRNG (reseed after fork)

The security benefits of a forking server having a re-inialized PRNG in
every child process are pretty obvious.  However, due to libraries
having all kinds of internal state, and programs getting compiled with
many different versions of each library, it is unreasonable to expect
calling programs to re-initialize everything manually after fork.

A further complication is the proliferation of clone flags, programs
bypassing glibc's functions to call clone directly, and programs calling
unshare, causing the glibc pthread_atfork hook to not get called.

It would be better to have the kernel take care of this automatically.

The patch also adds MADV_KEEPONFORK, to undo the effects of a prior
MADV_WIPEONFORK.

This is similar to the OpenBSD minherit syscall with MAP_INHERIT_ZERO:

    https://man.openbsd.org/minherit.2

[akpm@linux-foundation.org: numerically order arch/parisc/include/uapi/asm/mman.h #defines]
Link: http://lkml.kernel.org/r/20170811212829.29186-3-riel@redhat.com
Signed-off-by: Rik van Riel <riel@redhat.com>
Reported-by: Florian Weimer <fweimer@redhat.com>
Reported-by: Colm MacCártaigh <colm@allcosts.net>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Kees Cook <keescook@chromium.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Cc: <linux-api@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2017-09-06 17:27:30 -07:00
..
kasan Merge branch 'linus' into locking/core, to pick up fixes 2017-08-10 12:20:53 +02:00
backing-dev.c bdi: Drop 'parent' argument from bdi_register[_va]() 2017-04-20 12:09:55 -06:00
balloon_compaction.c mm/balloon_compaction.c: don't zero ballooned pages 2017-08-10 15:54:07 -07:00
bootmem.c mm/bootmem.c: cosmetic improvement of code readability 2017-02-22 16:41:29 -08:00
cleancache.c fs: switch ->s_uuid to uuid_t 2017-06-05 16:59:12 +02:00
cma.c cma: fix calculation of aligned offset 2017-07-10 16:32:32 -07:00
cma.h cma: Store a name in the cma structure 2017-04-18 20:41:12 +02:00
cma_debug.c mm/cma_debug.c: fix stack corruption due to sprintf usage 2017-08-18 15:32:02 -07:00
compaction.c mm, compaction: skip over holes in __reset_isolation_suitable 2017-07-06 16:24:32 -07:00
debug.c mm: make tlb_flush_pending global 2017-08-10 15:54:07 -07:00
debug_page_ref.c
dmapool.c lib/vsprintf.c: remove %Z support 2017-02-27 18:43:47 -08:00
early_ioremap.c x86/mm: Add support to access boot related data in the clear 2017-07-18 11:38:02 +02:00
fadvise.c mm: fadvise: avoid expensive remote LRU cache draining after FADV_DONTNEED 2016-12-20 09:48:46 -08:00
failslab.c
filemap.c mm: use find_get_pages_range() in filemap_range_has_page() 2017-09-06 17:27:27 -07:00
frame_vector.c treewide: use kv[mz]alloc* rather than opencoded variants 2017-05-08 17:15:13 -07:00
frontswap.c
gup.c mm/gup: make __gup_device_* require THP 2017-09-06 17:27:26 -07:00
highmem.c
huge_memory.c mm: hugetlb: clear target sub-page last when clearing huge page 2017-09-06 17:27:30 -07:00
hugetlb.c mm, hugetlb: do not allocate non-migrateable gigantic pages from movable zones 2017-09-06 17:27:29 -07:00
hugetlb_cgroup.c
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, oom: do not rely on TIF_MEMDIE for memory reserves access 2017-09-06 17:27:30 -07:00
interval_tree.c
Kconfig mm, devm_memremap_pages: use multi-order radix for ZONE_DEVICE lookups 2017-09-06 17:27:29 -07:00
Kconfig.debug mm: enable page poisoning early at boot 2017-05-03 15:52:10 -07:00
khugepaged.c mm: make PR_SET_THP_DISABLE immediately active 2017-07-10 16:32:31 -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
kmemleak.c mm: kmemleak: treat vm_struct as alternative reference to vmalloc'ed objects 2017-07-06 16:24:34 -07:00
ksm.c mm/ksm.c: constify attribute_group structures 2017-09-06 17:27:27 -07:00
list_lru.c mm/list_lru.c: fix list_lru_count_node() to be race free 2017-07-10 16:32:33 -07:00
maccess.c
madvise.c mm,fork: introduce MADV_WIPEONFORK 2017-09-06 17:27:30 -07:00
Makefile percpu: expose statistics about percpu memory via debugfs 2017-06-20 15:31:38 -04:00
memblock.c mm/memblock.c: reversed logic in memblock_discard() 2017-08-25 16:12:46 -07:00
memcontrol.c mm: replace TIF_MEMDIE checks by tsk_is_oom_victim 2017-09-06 17:27:30 -07:00
memory-failure.c x86/mm, mm/hwpoison: Clear PRESENT bit for kernel 1:1 mappings of poison pages 2017-08-17 10:30:49 +02:00
memory.c mm: hugetlb: clear target sub-page last when clearing huge page 2017-09-06 17:27:30 -07:00
memory_hotplug.c mm, memory_hotplug: get rid of zonelists_mutex 2017-09-06 17:27:26 -07:00
mempolicy.c mm/mempolicy: fix use after free when calling get_mempolicy 2017-08-18 15:32:02 -07:00
mempool.c sched/wait: Rename wait_queue_t => wait_queue_entry_t 2017-06-20 12:18:27 +02:00
memtest.c
migrate.c Sanitize 'move_pages()' permission checks 2017-08-20 13:26:27 -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
mmap.c mm: oom: let oom_reap_task and exit_mmap run concurrently 2017-09-06 17:27:30 -07:00
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/mmu_notifier: kill invalidate_page 2017-08-31 16:13:00 -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: migrate: prevent racy access to tlb_flush_pending 2017-08-10 15:54:07 -07:00
mremap.c mm/mremap: fail map duplication attempts for private mappings 2017-09-06 17:27:26 -07:00
msync.c
nobootmem.c mm: discard memblock data later 2017-08-18 15:32:01 -07:00
nommu.c mm: rename global_page_state to global_zone_page_state 2017-09-06 17:27:29 -07:00
oom_kill.c mm: oom: let oom_reap_task and exit_mmap run concurrently 2017-09-06 17:27:30 -07:00
page-writeback.c mm: rename global_page_state to global_zone_page_state 2017-09-06 17:27:29 -07:00
page_alloc.c mm, oom: do not rely on TIF_MEMDIE for memory reserves access 2017-09-06 17:27:30 -07:00
page_counter.c
page_ext.c mm, page_ext: periodically reschedule during page_ext_init() 2017-09-06 17:27:26 -07:00
page_idle.c mm/page_idle.c: constify attribute_group structures 2017-09-06 17:27:27 -07:00
page_io.c mm: test code to write THP to swap device as a whole 2017-09-06 17:27:28 -07:00
page_isolation.c mm: unify new_node_page and alloc_migrate_target 2017-07-10 16:32:31 -07:00
page_owner.c mm, page_owner: don't grab zone->lock for init_pages_in_zone() 2017-09-06 17:27:26 -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/hugetlb: add size parameter to huge_pte_offset() 2017-07-06 16:24:34 -07:00
pagewalk.c mm/hugetlb: add size parameter to huge_pte_offset() 2017-07-06 16:24:34 -07:00
percpu-internal.h percpu: fix early calls for spinlock in pcpu_stats 2017-06-21 13:53:52 -04:00
percpu-km.c percpu: fix static checker warnings in pcpu_destroy_chunk 2017-06-29 11:23:38 -04:00
percpu-stats.c percpu: expose statistics about percpu memory via debugfs 2017-06-20 15:31:38 -04:00
percpu-vm.c percpu: fix static checker warnings in pcpu_destroy_chunk 2017-06-29 11:23:38 -04:00
percpu.c percpu: resolve err may not be initialized in pcpu_alloc 2017-06-21 12:00:45 -04:00
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
readahead.c mm: don't cap request size based on read-ahead setting 2016-12-12 18:55:08 -08:00
rmap.c mm/rmap: update to new mmu_notifier semantic v2 2017-08-31 16:12:59 -07:00
rodata_test.c mm: remove rodata_test_data export, add pr_fmt 2017-05-03 15:52:09 -07:00
shmem.c mm, swap: VMA based swap readahead 2017-09-06 17:27:29 -07:00
slab.c mm: memcontrol: account slab stats per lruvec 2017-07-06 16:24:35 -07:00
slab.h locking/lockdep: Rework FS_RECLAIM annotation 2017-08-10 12:29:03 +02:00
slab_common.c mm: allow slab_nomerge to be set at build time 2017-07-06 16:24:31 -07:00
slob.c locking/lockdep: Rework FS_RECLAIM annotation 2017-08-10 12:29:03 +02:00
slub.c mm/slub.c: constify attribute_group structures 2017-09-06 17:27:27 -07:00
sparse-vmemmap.c mm, sparse, page_ext: drop ugly N_HIGH_MEMORY branches for allocations 2017-09-06 17:27:26 -07:00
sparse.c mm, sparse, page_ext: drop ugly N_HIGH_MEMORY branches for allocations 2017-09-06 17:27:26 -07:00
swap.c mm: remove nr_pages argument from pagevec_lookup{,_range}() 2017-09-06 17:27:27 -07:00
swap_cgroup.c mm, THP, swap: delay splitting THP during swap out 2017-07-06 16:24:31 -07:00
swap_slots.c mm/swap_slots.c: don't disable preemption while taking the per-CPU cache 2017-07-10 16:32:32 -07:00
swap_state.c mm, swap: add sysfs interface for VMA based swap readahead 2017-09-06 17:27:29 -07:00
swapfile.c swap: choose swap device according to numa node 2017-09-06 17:27:30 -07:00
truncate.c mm/truncate.c: fix THP handling in invalidate_mapping_pages() 2017-07-10 16:32:32 -07:00
usercopy.c mm/usercopy: Drop extra is_vmalloc_or_module() check 2017-04-05 12:30:18 -07:00
userfaultfd.c userfaultfd: shmem: wire up shmem_mfill_zeropage_pte 2017-09-06 17:27:28 -07:00
util.c mm: rename global_page_state to global_zone_page_state 2017-09-06 17:27:29 -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.c: don't reinvent the wheel but use existing llist API 2017-09-06 17:27:29 -07:00
vmpressure.c mm, vmpressure: pass-through notification support 2017-07-10 16:32:31 -07:00
vmscan.c mm, THP, swap: add THP swapping out fallback counting 2017-09-06 17:27:28 -07:00
vmstat.c mm, swap: add swap readahead hit statistics 2017-09-06 17:27:29 -07:00
workingset.c mm: memcontrol: per-lruvec stats infrastructure 2017-07-06 16:24:35 -07:00
z3fold.c z3fold: use per-cpu unbuddied lists 2017-09-06 17:27:30 -07:00
zbud.c
zpool.c
zsmalloc.c zsmalloc: zs_page_migrate: skip unnecessary loops but not return -EBUSY if zspage is not inuse 2017-09-06 17:27:26 -07:00
zswap.c mm/zswap.c: delete an error message for a failed memory allocation in zswap_dstmem_prepare() 2017-07-06 16:24:35 -07:00