The patch titled
Subject: fs/proc/kcore: drop KCORE_REMAP and KCORE_OTHER
has been added to the -mm tree. Its filename is
fs-proc-kcore-drop-kcore_remap-and-kcore_other.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/fs-proc-kcore-drop-kcore_remap-and-kcore_other.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/fs-proc-kcore-drop-kcore_remap-and-kcore_other.patch
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------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: fs/proc/kcore: drop KCORE_REMAP and KCORE_OTHER
Patch series "fs/proc/kcore: don't read offline sections, logically offline pages and hwpoisoned pages", v2.
Looking for places where the kernel might unconditionally read
PageOffline() pages, I stumbled over /proc/kcore; turns out /proc/kcore
needs some more love to not touch some other pages we really don't want to
read -- i.e., hwpoisoned ones.
Examples for PageOffline() pages are pages inflated in a balloon, memory
unplugged via virtio-mem, and partially-present sections in memory added
by the Hyper-V balloon.
When reading pages inflated in a balloon, we essentially produce
unnecessary load in the hypervisor; holes in partially present sections in
case of Hyper-V are not accessible and already were a problem for
/proc/vmcore, fixed in makedumpfile by detecting PageOffline() pages. In
the future, virtio-mem might disallow reading unplugged memory -- marked
as PageOffline() -- in some environments, resulting in undefined behavior
when accessed; therefore, I'm trying to identify and rework all these
(corner) cases.
With this series, there is really only access via /dev/mem, /proc/vmcore
and kdb left after I ripped out /dev/kmem. kdb is an advanced corner-case
use case -- we won't care for now if someone explicitly tries to do nasty
things by reading from/writing to physical addresses we better not touch.
/dev/mem is a use case we won't support for virtio-mem, at least for now,
so we'll simply disallow mapping any virtio-mem memory via /dev/mem next.
/proc/vmcore is really only a problem when dumping the old kernel via
something that's not makedumpfile (read: basically never), however, we'll
try sanitizing that as well in the second kernel in the future.
Tested via kcore_dump:
https://github.com/schlafwandler/kcore_dump
This patch (of 6):
Commit db779ef67ffe ("proc/kcore: Remove unused kclist_add_remap()")
removed the last user of KCORE_REMAP.
Commit 595dd46ebfc1 ("vfs/proc/kcore, x86/mm/kcore: Fix SMAP fault when
dumping vsyscall user page") removed the last user of KCORE_OTHER.
Let's drop both types. While at it, also drop vaddr in "struct
kcore_list", used by KCORE_REMAP only.
Link: https://lkml.kernel.org/r/20210514172247.176750-1-david@xxxxxxxxxx
Link: https://lkml.kernel.org/r/20210514172247.176750-2-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: "Michael S. Tsirkin" <mst@xxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Cc: Oscar Salvador <osalvador@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Cc: Steven Price <steven.price@xxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Aili Yao <yaoaili@xxxxxxxxxxxx>
Cc: Jiri Bohac <jbohac@xxxxxxx>
Cc: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Cc: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
Cc: Wei Liu <wei.liu@xxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/kcore.c | 7 ++-----
include/linux/kcore.h | 3 ---
2 files changed, 2 insertions(+), 8 deletions(-)
--- a/fs/proc/kcore.c~fs-proc-kcore-drop-kcore_remap-and-kcore_other
+++ a/fs/proc/kcore.c
@@ -380,11 +380,8 @@ read_kcore(struct file *file, char __use
phdr->p_type = PT_LOAD;
phdr->p_flags = PF_R | PF_W | PF_X;
phdr->p_offset = kc_vaddr_to_offset(m->addr) + data_offset;
- if (m->type == KCORE_REMAP)
- phdr->p_vaddr = (size_t)m->vaddr;
- else
- phdr->p_vaddr = (size_t)m->addr;
- if (m->type == KCORE_RAM || m->type == KCORE_REMAP)
+ phdr->p_vaddr = (size_t)m->addr;
+ if (m->type == KCORE_RAM)
phdr->p_paddr = __pa(m->addr);
else if (m->type == KCORE_TEXT)
phdr->p_paddr = __pa_symbol(m->addr);
--- a/include/linux/kcore.h~fs-proc-kcore-drop-kcore_remap-and-kcore_other
+++ a/include/linux/kcore.h
@@ -11,14 +11,11 @@ enum kcore_type {
KCORE_RAM,
KCORE_VMEMMAP,
KCORE_USER,
- KCORE_OTHER,
- KCORE_REMAP,
};
struct kcore_list {
struct list_head list;
unsigned long addr;
- unsigned long vaddr;
size_t size;
int type;
};
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
perf-map_executable-does-not-indicate-vm_mayexec.patch
binfmt-remove-in-tree-usage-of-map_executable.patch
mm-ignore-map_executable-in-ksys_mmap_pgoff.patch
mm-make-variable-names-for-populate_vma_page_range-consistent.patch
mm-madvise-introduce-madv_populate_readwrite-to-prefault-page-tables.patch
maintainers-add-tools-testing-selftests-vm-to-memory-management.patch
selftests-vm-add-protection_keys_32-protection_keys_64-to-gitignore.patch
selftests-vm-add-test-for-madv_populate_readwrite.patch
fs-proc-kcore-drop-kcore_remap-and-kcore_other.patch
fs-proc-kcore-pfn_is_ram-check-only-applies-to-kcore_ram.patch
fs-proc-kcore-dont-read-offline-sections-logically-offline-pages-and-hwpoisoned-pages.patch
mm-introduce-page_offline_beginendfreezethaw-to-synchronize-setting-pageoffline.patch
virtio-mem-use-page_offline_startend-when-setting-pageoffline.patch
fs-proc-kcore-use-page_offline_freezethaw.patch
