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authorDavid Hildenbrand <david@redhat.com>2021-07-01 04:50:03 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2021-07-01 06:47:28 +0300
commit3c36b419b111e28a657e6534aae07964a98a5ca9 (patch)
treeb472c0fb20b404297407bfc81a8d811c8f4bd5cc /fs/proc
parent8d719afcb34434ebfa7911338d8c777eca8452b0 (diff)
downloadlinux-3c36b419b111e28a657e6534aae07964a98a5ca9.tar.xz
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", v3. 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/20210526093041.8800-1-david@redhat.com Link: https://lkml.kernel.org/r/20210526093041.8800-2-david@redhat.com Signed-off-by: David Hildenbrand <david@redhat.com> Reviewed-by: Mike Rapoport <rppt@linux.ibm.com> Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Alexey Dobriyan <adobriyan@gmail.com> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org> Cc: Oscar Salvador <osalvador@suse.de> Cc: Michal Hocko <mhocko@suse.com> Cc: Roman Gushchin <guro@fb.com> Cc: Alex Shi <alex.shi@linux.alibaba.com> Cc: Steven Price <steven.price@arm.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Aili Yao <yaoaili@kingsoft.com> Cc: Jiri Bohac <jbohac@suse.cz> Cc: "K. Y. Srinivasan" <kys@microsoft.com> Cc: Haiyang Zhang <haiyangz@microsoft.com> Cc: Stephen Hemminger <sthemmin@microsoft.com> Cc: Wei Liu <wei.liu@kernel.org> Cc: Naoya Horiguchi <naoya.horiguchi@nec.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/proc')
-rw-r--r--fs/proc/kcore.c7
1 files changed, 2 insertions, 5 deletions
diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index 4d2e64e9016c..09f77d3c6e15 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -380,11 +380,8 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
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);