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Sergei Antonov 70427f6e9e mm: bring back update_mmu_cache() to finish_fault()
Running this test program on ARMv4 a few times (sometimes just once)
reproduces the bug.

int main()
{
        unsigned i;
        char paragon[SIZE];
        void* ptr;

        memset(paragon, 0xAA, SIZE);
        ptr = mmap(NULL, SIZE, PROT_READ | PROT_WRITE,
                   MAP_ANON | MAP_SHARED, -1, 0);
        if (ptr == MAP_FAILED) return 1;
        printf("ptr = %p\n", ptr);
        for (i=0;i<10000;i++){
                memset(ptr, 0xAA, SIZE);
                if (memcmp(ptr, paragon, SIZE)) {
                        printf("Unexpected bytes on iteration %u!!!\n", i);
                        break;
                }
        }
        munmap(ptr, SIZE);
}

In the "ptr" buffer there appear runs of zero bytes which are aligned
by 16 and their lengths are multiple of 16.

Linux v5.11 does not have the bug, "git bisect" finds the first bad commit:
f9ce0be71d ("mm: Cleanup faultaround and finish_fault() codepaths")

Before the commit update_mmu_cache() was called during a call to
filemap_map_pages() as well as finish_fault(). After the commit
finish_fault() lacks it.

Bring back update_mmu_cache() to finish_fault() to fix the bug.
Also call update_mmu_tlb() only when returning VM_FAULT_NOPAGE to more
closely reproduce the code of alloc_set_pte() function that existed before
the commit.

On many platforms update_mmu_cache() is nop:
 x86, see arch/x86/include/asm/pgtable
 ARMv6+, see arch/arm/include/asm/tlbflush.h
So, it seems, few users ran into this bug.

Link: https://lkml.kernel.org/r/20220908204809.2012451-1-saproj@gmail.com
Fixes: f9ce0be71d ("mm: Cleanup faultaround and finish_fault() codepaths")
Signed-off-by: Sergei Antonov <saproj@gmail.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Will Deacon <will@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-09-26 12:14:34 -07:00
arch powerpc/64s/radix: don't need to broadcast IPI for radix pmd collapse flush 2022-09-26 12:14:33 -07:00
block block-6.0-2022-08-26 2022-08-26 11:05:54 -07:00
certs Kbuild updates for v5.20 2022-08-10 10:40:41 -07:00
crypto crypto: blake2b: effectively disable frame size warning 2022-08-10 17:59:11 -07:00
Documentation Misc fixes: 2022-08-28 10:10:23 -07:00
drivers Seventeen hotfixes. Mostly memory management things. Ten patches are 2022-08-28 14:49:59 -07:00
fs xfs: fix SB_BORN check in xfs_dax_notify_failure() 2022-09-11 16:22:29 -07:00
include mm/memory-failure: fix detection of memory_failure() handlers 2022-09-11 16:22:29 -07:00
init arm64 fixes for -rc3 2022-08-26 11:32:53 -07:00
io_uring io_uring/net: save address for sendzc async execution 2022-08-25 07:52:30 -06:00
ipc Updates to various subsystems which I help look after. lib, ocfs2, 2022-08-07 10:03:24 -07:00
kernel Seventeen hotfixes. Mostly memory management things. Ten patches are 2022-08-28 14:49:59 -07:00
lib bitmap fixes for v6.0-rc3 2022-08-28 14:36:27 -07:00
LICENSES LICENSES/LGPL-2.1: Add LGPL-2.1-or-later as valid identifiers 2021-12-16 14:33:10 +01:00
mm mm: bring back update_mmu_cache() to finish_fault() 2022-09-26 12:14:34 -07:00
net Including fixes from ipsec and netfilter (with one broken Fixes tag). 2022-08-25 14:03:58 -07:00
samples Tracing updates for 5.20 / 6.0 2022-08-05 09:41:12 -07:00
scripts asm goto: eradicate CC_HAS_ASM_GOTO 2022-08-21 10:06:28 -07:00
security hardening fixes for v6.0-rc2 2022-08-19 13:56:14 -07:00
sound sound fixes for 6.0-rc2 2022-08-19 09:46:11 -07:00
tools tools: fix compilation after gfp_types.h split 2022-09-11 16:22:31 -07:00
usr Not a lot of material this cycle. Many singleton patches against various 2022-05-27 11:22:03 -07:00
virt KVM: Drop unnecessary initialization of "ops" in kvm_ioctl_create_device() 2022-08-19 04:05:43 -04:00
.clang-format PCI/DOE: Add DOE mailbox support functions 2022-07-19 15:38:04 -07:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore kbuild: split the second line of *.mod into *.usyms 2022-05-08 03:16:59 +09:00
.mailmap .mailmap: update Luca Ceresoli's e-mail address 2022-08-28 14:02:46 -07:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS drm for 5.20/6.0 2022-08-03 19:52:08 -07:00
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 bitmap fixes for v6.0-rc3 2022-08-28 14:36:27 -07:00
Makefile Linux 6.0-rc3 2022-08-28 15:05:29 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.