linux-kernel - [PATCH v5 1/3] kexec: modify the meaning of the end parameter in kimage_is_destination

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Date: Sun, 17 Dec 2023 11:35:26 +0800
From: Yuntao Wang <ytcoode@...il.com>
To: linux-kernel@...r.kernel.org,
	kexec@...ts.infradead.org,
	x86@...nel.org
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Jonathan Corbet <corbet@....net>,
	Eric Biederman <ebiederm@...ssion.com>,
	Baoquan He <bhe@...hat.com>,
	Yuntao Wang <ytcoode@...il.com>
Subject: [PATCH v5 1/3] kexec: modify the meaning of the end parameter in kimage_is_destination_range()

The end parameter received by kimage_is_destination_range() should be the
last valid byte address of the target memory segment plus 1. However, in
the locate_mem_hole_bottom_up() and locate_mem_hole_top_down() functions,
the corresponding value passed to kimage_is_destination_range() is the last
valid byte address of the target memory segment, which is 1 less.

There are two ways to fix this bug. We can either correct the logic of the
locate_mem_hole_bottom_up() and locate_mem_hole_top_down() functions, or we
can fix kimage_is_destination_range() by making the end parameter represent
the last valid byte address of the target memory segment. Here, we choose
the second approach.

Due to the modification to kimage_is_destination_range(), we also need to
adjust its callers, such as kimage_alloc_normal_control_pages() and
kimage_alloc_page().

Signed-off-by: Yuntao Wang <ytcoode@...il.com>
Acked-by: Baoquan He <bhe@...hat.com>
---
v1->v2:
  Fix this issue using the approach suggested by Eric and Baoquan.

v2->v3:
  Modify the assignment of eaddr as suggested by Baoquan.

v3->v4:
  `eaddr = epfn << PAGE_SHIFT - 1` causes a compilation warning, fix it.

v4->v5:
  No changes.

 kernel/kexec_core.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index be5642a4ec49..e3b1a699f087 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -276,8 +276,8 @@ int kimage_is_destination_range(struct kimage *image,
 		unsigned long mstart, mend;
 
 		mstart = image->segment[i].mem;
-		mend = mstart + image->segment[i].memsz;
-		if ((end > mstart) && (start < mend))
+		mend = mstart + image->segment[i].memsz - 1;
+		if ((end >= mstart) && (start <= mend))
 			return 1;
 	}
 
@@ -370,7 +370,7 @@ static struct page *kimage_alloc_normal_control_pages(struct kimage *image,
 		pfn   = page_to_boot_pfn(pages);
 		epfn  = pfn + count;
 		addr  = pfn << PAGE_SHIFT;
-		eaddr = epfn << PAGE_SHIFT;
+		eaddr = (epfn << PAGE_SHIFT) - 1;
 		if ((epfn >= (KEXEC_CONTROL_MEMORY_LIMIT >> PAGE_SHIFT)) ||
 			      kimage_is_destination_range(image, addr, eaddr)) {
 			list_add(&pages->lru, &extra_pages);
@@ -716,7 +716,7 @@ static struct page *kimage_alloc_page(struct kimage *image,
 
 		/* If the page is not a destination page use it */
 		if (!kimage_is_destination_range(image, addr,
-						  addr + PAGE_SIZE))
+						  addr + PAGE_SIZE - 1))
 			break;
 
 		/*
-- 
2.43.0