+ efi-unaccepted-do-not-let-proc-vmcore-try-to-access-unaccepted-memory.patch added to mm-unstable branch

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The patch titled
     Subject: efi/unaccepted: do not let /proc/vmcore try to access unaccepted memory
has been added to the -mm mm-unstable branch.  Its filename is
     efi-unaccepted-do-not-let-proc-vmcore-try-to-access-unaccepted-memory.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/efi-unaccepted-do-not-let-proc-vmcore-try-to-access-unaccepted-memory.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Subject: efi/unaccepted: do not let /proc/vmcore try to access unaccepted memory
Date: Mon, 11 Sep 2023 14:21:13 +0300

Patch series "Do not try to access unaccepted memory", v2.

Support for unaccepted memory was added recently, refer commit
dcdfdd40fa82 ("mm: Add support for unaccepted memory"), whereby
a virtual machine may need to accept memory before it can be used.

Plug a few gaps where RAM is exposed without checking if it is
unaccepted memory.


This patch (of 2):

Support for unaccepted memory was added recently, refer commit
dcdfdd40fa82 ("mm: Add support for unaccepted memory"), whereby a virtual
machine may need to accept memory before it can be used.

Do not let /proc/vmcore try to access unaccepted memory because it can
cause the guest to fail.

For /proc/vmcore, which is read-only, this means a read or mmap of
unaccepted memory will return zeros.

Link: https://lkml.kernel.org/r/20230911112114.91323-1-adrian.hunter@xxxxxxxxx
Link: https://lkml.kernel.org/r/20230911112114.91323-2-adrian.hunter@xxxxxxxxx
Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Dave Young <dyoung@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Tom Lendacky <thomas.lendacky@xxxxxxx>
Cc: Vivek Goyal <vgoyal@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---

 drivers/firmware/efi/unaccepted_memory.c |   20 ++++++++++++++++++++
 include/linux/mm.h                       |    7 +++++++
 2 files changed, 27 insertions(+)

--- a/drivers/firmware/efi/unaccepted_memory.c~efi-unaccepted-do-not-let-proc-vmcore-try-to-access-unaccepted-memory
+++ a/drivers/firmware/efi/unaccepted_memory.c
@@ -3,6 +3,7 @@
 #include <linux/efi.h>
 #include <linux/memblock.h>
 #include <linux/spinlock.h>
+#include <linux/crash_dump.h>
 #include <asm/unaccepted_memory.h>
 
 /* Protects unaccepted memory bitmap */
@@ -145,3 +146,22 @@ bool range_contains_unaccepted_memory(ph
 
 	return ret;
 }
+
+#ifdef CONFIG_PROC_VMCORE
+static bool unaccepted_memory_vmcore_pfn_is_ram(struct vmcore_cb *cb,
+						unsigned long pfn)
+{
+	return !pfn_is_unaccepted_memory(pfn);
+}
+
+static struct vmcore_cb vmcore_cb = {
+	.pfn_is_ram = unaccepted_memory_vmcore_pfn_is_ram,
+};
+
+static int __init unaccepted_memory_init_kdump(void)
+{
+	register_vmcore_cb(&vmcore_cb);
+	return 0;
+}
+core_initcall(unaccepted_memory_init_kdump);
+#endif /* CONFIG_PROC_VMCORE */
--- a/include/linux/mm.h~efi-unaccepted-do-not-let-proc-vmcore-try-to-access-unaccepted-memory
+++ a/include/linux/mm.h
@@ -4055,4 +4055,11 @@ static inline void accept_memory(phys_ad
 
 #endif
 
+static inline bool pfn_is_unaccepted_memory(unsigned long pfn)
+{
+	phys_addr_t paddr = pfn << PAGE_SHIFT;
+
+	return range_contains_unaccepted_memory(paddr, paddr + PAGE_SIZE);
+}
+
 #endif /* _LINUX_MM_H */
_

Patches currently in -mm which might be from adrian.hunter@xxxxxxxxx are

efi-unaccepted-do-not-let-proc-vmcore-try-to-access-unaccepted-memory.patch
proc-kcore-do-not-try-to-access-unaccepted-memory.patch




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