linux-kernel - [PATCH 1/3 v4] kexec: modify the meaning of the end parameter in kimage_is_destination

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Date: Sat, 16 Dec 2023 20:05:51 +0800
From: Yuntao Wang <ytcoode@...il.com>
To: bhe@...hat.com
Cc: akpm@...ux-foundation.org,
	bp@...en8.de,
	corbet@....net,
	dave.hansen@...ux.intel.com,
	ebiederm@...ssion.com,
	hpa@...or.com,
	kexec@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	mingo@...hat.com,
	tglx@...utronix.de,
	x86@...nel.org,
	ytcoode@...il.com
Subject: [PATCH 1/3 v4] 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>
---
v1->v2:
  Fix this issue using the approach suggested by Eric and Baoquan.

  As this patch is independent of the other patches in this series, I sent
  out the v2 patch separately. If it's inconvenient for anyone, I can
  resend the entire series again.

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

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

 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