[PATCH v3 00/20] Merge text_poke fixes and executable lockdowns

From: Rick Edgecombe
Date: Thu Feb 21 2019 - 18:50:55 EST

This patchset improves several overlapping issues around stale TLB entries and
W^X violations. It is combined from "x86/alternative: text_poke() enhancements
v7" [1] and "Donât leave executable TLB entries to freed pages v2" [2] patchsets
that were conflicting.

The related issues that this fixes:
1. Fixmap PTEs that are used for patching are available for access from
other cores and might be exploited. They are not even flushed from
the TLB in remote cores, so the risk is even higher. Address this
issue by introducing a temporary mm that is only used during
patching. Unfortunately, due to init ordering, fixmap is still used
during boot-time patching. Future patches can eliminate the need for
2. Missing lockdep assertion to ensure text_mutex is taken. It is
actually not always taken, so fix the instances that were found not
to take the lock (although they should be safe even without taking
the lock).
3. Module_alloc returning memory that is RWX until a module is finished
4. Sometimes when memory is freed via the module subsystem, an
executable permissioned TLB entry can remain to a freed page. If the
page is re-used to back an address that will receive data from
userspace, it can result in user data being mapped as executable in
the kernel. The root of this behavior is vfree lazily flushing the
TLB, but not lazily freeing the underlying pages.

Changes v2 to v3:
- Fix commit messages and comments [Boris]
- Remove unnecessary local variables [Boris]
- Rename set_alias_*() functions [Boris, Andy]
- Save/restore DR registers when using temporary mm
- Move line deletion from patch 10 to patch 17

Changes v1 to v2:
- Adding âReviewed-by tagâ [Masami]
- Comment instead of code to warn against module removal while
patching [Masami]
- Avoiding open-coded TLB flush [Andy]
- Remove "This patch" [Borislav Petkov]
- Not set global bit during text poking [Andy, hpa]
- Add Ack from [Pavel Machek]
- Split patch 16 "Plug in new special vfree flag" into 4 patches (16-19)
to make it easier to review. There were no code changes.

The changes from "Donât leave executable TLB entries to freed pages
v2" to v1:
- Add support for case of hibernate trying to save an unmapped page
on the directmap. (Ard Biesheuvel)
- No week arch breakout for vfree-ing special memory (Andy Lutomirski)
- Avoid changing deferred free code by moving modules init free to work
queue (Andy Lutomirski)
- Plug in new flag for kprobes and ftrace
- More arch generic names for set_pages functions (Ard Biesheuvel)
- Fix for TLB not always flushing the directmap (Nadav Amit)

Changes from "x86/alternative: text_poke() enhancements v7" to v1
- Fix build failure on CONFIG_RANDOMIZE_BASE=n (Rick)
- Remove text_poke usage from ftrace (Nadav)

[1] https://lkml.org/lkml/2018/12/5/200
[2] https://lkml.org/lkml/2018/12/11/1571

Andy Lutomirski (1):
x86/mm: Introduce temporary mm structs

Nadav Amit (12):
x86/jump_label: Use text_poke_early() during early init
x86/mm: Save DRs when loading a temporary mm
fork: Provide a function for copying init_mm
x86/alternative: Initialize temporary mm for patching
x86/alternative: Use temporary mm for text poking
x86/kgdb: Avoid redundant comparison of patched code
x86/ftrace: Set trampoline pages as executable
x86/kprobes: Set instruction page as executable
x86/module: Avoid breaking W^X while loading modules
x86/jump-label: Remove support for custom poker
x86/alternative: Remove the return value of text_poke_*()
x86/alternative: Comment about module removal races

Rick Edgecombe (7):
x86/mm/cpa: Add set_direct_map_ functions
mm: Make hibernate handle unmapped pages
vmalloc: Add flag for free of special permsissions
modules: Use vmalloc special flag
bpf: Use vmalloc special flag
x86/ftrace: Use vmalloc special flag
x86/kprobes: Use vmalloc special flag

arch/Kconfig | 4 +
arch/x86/Kconfig | 1 +
arch/x86/include/asm/fixmap.h | 2 -
arch/x86/include/asm/mmu_context.h | 58 ++++++++++
arch/x86/include/asm/pgtable.h | 3 +
arch/x86/include/asm/set_memory.h | 3 +
arch/x86/include/asm/text-patching.h | 6 +-
arch/x86/kernel/alternative.c | 153 +++++++++++++++++++++------
arch/x86/kernel/ftrace.c | 14 ++-
arch/x86/kernel/jump_label.c | 21 ++--
arch/x86/kernel/kgdb.c | 14 +--
arch/x86/kernel/kprobes/core.c | 19 +++-
arch/x86/kernel/module.c | 2 +-
arch/x86/mm/init_64.c | 36 +++++++
arch/x86/mm/pageattr.c | 16 +--
arch/x86/xen/mmu_pv.c | 2 -
include/linux/filter.h | 18 +---
include/linux/mm.h | 18 ++--
include/linux/sched/task.h | 1 +
include/linux/set_memory.h | 10 ++
include/linux/vmalloc.h | 13 +++
init/main.c | 3 +
kernel/bpf/core.c | 1 -
kernel/fork.c | 24 +++--
kernel/module.c | 82 +++++++-------
kernel/power/snapshot.c | 5 +-
mm/page_alloc.c | 7 +-
mm/vmalloc.c | 113 ++++++++++++++++----
28 files changed, 475 insertions(+), 174 deletions(-)