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3c36b419b1
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): Commitdb779ef67f("proc/kcore: Remove unused kclist_add_remap()") removed the last user of KCORE_REMAP. Commit595dd46ebf("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>
47 lines
891 B
C
47 lines
891 B
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* /proc/kcore definitions
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*/
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#ifndef _LINUX_KCORE_H
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#define _LINUX_KCORE_H
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enum kcore_type {
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KCORE_TEXT,
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KCORE_VMALLOC,
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KCORE_RAM,
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KCORE_VMEMMAP,
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KCORE_USER,
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};
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struct kcore_list {
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struct list_head list;
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unsigned long addr;
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size_t size;
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int type;
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};
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struct vmcore {
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struct list_head list;
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unsigned long long paddr;
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unsigned long long size;
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loff_t offset;
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};
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struct vmcoredd_node {
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struct list_head list; /* List of dumps */
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void *buf; /* Buffer containing device's dump */
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unsigned int size; /* Size of the buffer */
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};
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#ifdef CONFIG_PROC_KCORE
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void __init kclist_add(struct kcore_list *, void *, size_t, int type);
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extern int __init register_mem_pfn_is_ram(int (*fn)(unsigned long pfn));
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#else
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static inline
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void kclist_add(struct kcore_list *new, void *addr, size_t size, int type)
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{
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}
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#endif
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#endif /* _LINUX_KCORE_H */
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