+ kexec-copy-only-happens-before-uchunk-goes-to-zero.patch added to mm-nonmm-unstable branch

+ kexec-copy-only-happens-before-uchunk-goes-to-zero.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: kexec: copy only happens before uchunk goes to zero
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     kexec-copy-only-happens-before-uchunk-goes-to-zero.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kexec-copy-only-happens-before-uchunk-goes-to-zero.patch

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

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   b) Prefer to cc a suitable mailing list as well
   c) Ideally: find the original patch on the mailing list and do a
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------------------------------------------------------
From: "yang.zhang" <yang.zhang@hexintek.com>
Subject: kexec: copy only happens before uchunk goes to zero
Date: Thu, 22 Feb 2024 17:21:19 +0800

When loading segments, ubytes is <= mbytes.  When ubytes is exhausted,
there could be remaining mbytes.  Then in the while loop, the buf pointer
advancing with mchunk will causing meaningless reading even though it
doesn't harm.

So let's change to make sure that all of the copying and the rest only
happens before uchunk goes to zero.

Link: https://lkml.kernel.org/r/20240222092119.5602-1-gaoshanliukou@163.com
Signed-off-by: yang.zhang <yang.zhang@hexintek.com>
Acked-by: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/kexec_core.c |   44 ++++++++++++++++++++++--------------------
 1 file changed, 24 insertions(+), 20 deletions(-)

--- a/kernel/kexec_core.c~kexec-copy-only-happens-before-uchunk-goes-to-zero
+++ a/kernel/kexec_core.c
@@ -750,22 +750,24 @@ static int kimage_load_normal_segment(st
 				PAGE_SIZE - (maddr & ~PAGE_MASK));
 		uchunk = min(ubytes, mchunk);
 
-		/* For file based kexec, source pages are in kernel memory */
-		if (image->file_mode)
-			memcpy(ptr, kbuf, uchunk);
-		else
-			result = copy_from_user(ptr, buf, uchunk);
+		if (uchunk) {
+			/* For file based kexec, source pages are in kernel memory */
+			if (image->file_mode)
+				memcpy(ptr, kbuf, uchunk);
+			else
+				result = copy_from_user(ptr, buf, uchunk);
+			ubytes -= uchunk;
+			if (image->file_mode)
+				kbuf += uchunk;
+			else
+				buf += uchunk;
+		}
 		kunmap_local(ptr);
 		if (result) {
 			result = -EFAULT;
 			goto out;
 		}
-		ubytes -= uchunk;
 		maddr  += mchunk;
-		if (image->file_mode)
-			kbuf += mchunk;
-		else
-			buf += mchunk;
 		mbytes -= mchunk;
 
 		cond_resched();
@@ -817,11 +819,18 @@ static int kimage_load_crash_segment(str
 			memset(ptr + uchunk, 0, mchunk - uchunk);
 		}
 
-		/* For file based kexec, source pages are in kernel memory */
-		if (image->file_mode)
-			memcpy(ptr, kbuf, uchunk);
-		else
-			result = copy_from_user(ptr, buf, uchunk);
+		if (uchunk) {
+			/* For file based kexec, source pages are in kernel memory */
+			if (image->file_mode)
+				memcpy(ptr, kbuf, uchunk);
+			else
+				result = copy_from_user(ptr, buf, uchunk);
+			ubytes -= uchunk;
+			if (image->file_mode)
+				kbuf += uchunk;
+			else
+				buf += uchunk;
+		}
 		kexec_flush_icache_page(page);
 		kunmap_local(ptr);
 		arch_kexec_pre_free_pages(page_address(page), 1);
@@ -829,12 +838,7 @@ static int kimage_load_crash_segment(str
 			result = -EFAULT;
 			goto out;
 		}
-		ubytes -= uchunk;
 		maddr  += mchunk;
-		if (image->file_mode)
-			kbuf += mchunk;
-		else
-			buf += mchunk;
 		mbytes -= mchunk;
 
 		cond_resched();
_

Patches currently in -mm which might be from yang.zhang@hexintek.com are

kexec-copy-only-happens-before-uchunk-goes-to-zero.patch

Re: 答复: + kexec-copy-only-happens-before-uchunk-goes-to-zero.patch added to mm-nonmm-unstable branch

[bhe]

On 03/05/24 at 02:25am, 张洋 wrote:
> Thank you for your reply
> 
> I am not very clear about the next process. I would like to know if there is anything I need to do next. I hope you will not hesitate to give me your advice.
> Thanks again.

No, you don't need to do anything. Andrew has been helping pick 
kexec/kdump patches into his tree, then will submit them to linus's tree
during next merging window if code is reliable.

答复: 答复: + kexec-copy-only-happens-before-uchunk-goes-to-zero.patch added to mm-nonmm-unstable branch

[张洋]

Ok, thanks.
________________________________________
发件人: bhe@redhat.com <bhe@redhat.com>
发送时间: 2024年3月5日 13:19:07
收件人: 张洋
抄送: Andrew Morton; mm-commits@vger.kernel.org
主题: Re: 答复: + kexec-copy-only-happens-before-uchunk-goes-to-zero.patch added to mm-nonmm-unstable branch

On 03/05/24 at 02:25am, 张洋 wrote:
> Thank you for your reply
>
> I am not very clear about the next process. I would like to know if there is anything I need to do next. I hope you will not hesitate to give me your advice.
> Thanks again.

No, you don't need to do anything. Andrew has been helping pick
kexec/kdump patches into his tree, then will submit them to linus's tree
during next merging window if code is reliable.

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