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James Houghton c2134ed532 arm64: mm: Always make sw-dirty PTEs hw-dirty in pte_modify 
commit 3c0696076a upstream.

It is currently possible for a userspace application to enter an
infinite page fault loop when using HugeTLB pages implemented with
contiguous PTEs when HAFDBS is not available. This happens because:

1. The kernel may sometimes write PTEs that are sw-dirty but hw-clean
   (PTE_DIRTY | PTE_RDONLY | PTE_WRITE).

2. If, during a write, the CPU uses a sw-dirty, hw-clean PTE in handling
   the memory access on a system without HAFDBS, we will get a page
   fault.

3. HugeTLB will check if it needs to update the dirty bits on the PTE.
   For contiguous PTEs, it will check to see if the pgprot bits need
   updating. In this case, HugeTLB wants to write a sequence of
   sw-dirty, hw-dirty PTEs, but it finds that all the PTEs it is about
   to overwrite are all pte_dirty() (pte_sw_dirty() => pte_dirty()),
   so it thinks no update is necessary.

We can get the kernel to write a sw-dirty, hw-clean PTE with the
following steps (showing the relevant VMA flags and pgprot bits):

i.   Create a valid, writable contiguous PTE.
       VMA vmflags:     VM_SHARED | VM_READ | VM_WRITE
       VMA pgprot bits: PTE_RDONLY | PTE_WRITE
       PTE pgprot bits: PTE_DIRTY | PTE_WRITE

ii.  mprotect the VMA to PROT_NONE.
       VMA vmflags:     VM_SHARED
       VMA pgprot bits: PTE_RDONLY
       PTE pgprot bits: PTE_DIRTY | PTE_RDONLY

iii. mprotect the VMA back to PROT_READ | PROT_WRITE.
       VMA vmflags:     VM_SHARED | VM_READ | VM_WRITE
       VMA pgprot bits: PTE_RDONLY | PTE_WRITE
       PTE pgprot bits: PTE_DIRTY | PTE_WRITE | PTE_RDONLY

Make it impossible to create a writeable sw-dirty, hw-clean PTE with
pte_modify(). Such a PTE should be impossible to create, and there may
be places that assume that pte_dirty() implies pte_hw_dirty().

Signed-off-by: James Houghton <jthoughton@google.com>
Fixes: 031e6e6b4e ("arm64: hugetlb: Avoid unnecessary clearing in huge_ptep_set_access_flags")
Cc: <stable@vger.kernel.org>
Acked-by: Will Deacon <will@kernel.org>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Link: https://lore.kernel.org/r/20231204172646.2541916-3-jthoughton@google.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2023-12-20 15:17:41 +01:00
arch arm64: mm: Always make sw-dirty PTEs hw-dirty in pte_modify 2023-12-20 15:17:41 +01:00
block blk-cgroup: bypass blkcg_deactivate_policy after destroying 2023-12-20 15:17:39 +01:00
certs certs/blacklist_hashes.c: fix const confusion in certs blacklist 2022-06-22 14:22:01 +02:00
crypto crypto: pcrypt - Fix hungtask for PADATA_RESET 2023-11-28 16:56:18 +00:00
Documentation docs/process/howto: Replace C89 with C11 2023-12-13 18:36:46 +01:00
drivers soundwire: stream: fix NULL pointer dereference for multi_link 2023-12-20 15:17:41 +01:00
fs ext4: prevent the normalized size from exceeding EXT_MAX_BLOCKS 2023-12-20 15:17:41 +01:00
include asm-generic: qspinlock: fix queued_spin_value_unlocked() implementation 2023-12-20 15:17:40 +01:00
init proc: sysctl: prevent aliased sysctls from getting passed to init 2023-12-03 07:31:24 +01:00
io_uring io_uring/af_unix: disable sending io_uring over sockets 2023-12-13 18:36:46 +01:00
ipc ipc/sem: Fix dangling sem_array access in semtimedop race 2022-12-08 11:28:45 +01:00
kernel perf: Fix perf_event_validate_size() lockdep splat 2023-12-20 15:17:41 +01:00
lib parisc: Drop the HP-UX ENOSYM and EREMOTERELEASE error codes 2023-12-08 08:48:02 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm memblock: allow to specify flags with memblock_add_node() 2023-12-20 15:17:33 +01:00
net appletalk: Fix Use-After-Free in atalk_ioctl 2023-12-20 15:17:37 +01:00
samples samples/hw_breakpoint: fix building without module unloading 2023-09-23 11:10:01 +02:00
scripts sign-file: Fix incorrect return values check 2023-12-20 15:17:37 +01:00
security KEYS: trusted: Rollback init_trusted() consistently 2023-11-28 16:56:30 +00:00
sound ALSA: hda/realtek: Apply mute LED quirk for HP15-db 2023-12-20 15:17:38 +01:00
tools tools headers UAPI: Sync linux/perf_event.h with the kernel sources 2023-12-13 18:36:46 +01:00
usr usr/include/Makefile: add linux/nfc.h to the compile-test coverage 2022-02-01 17:27:15 +01:00
virt KVM: Grab a reference to KVM for VM and vCPU stats file descriptors 2023-08-03 10:22:40 +02:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS iio: stx104: Move to addac subdirectory 2023-08-26 14:23:27 +02:00
Makefile Linux 5.15.143 2023-12-13 18:36:50 +01:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.