diff mbox series

[V3] kexec: copy only happens before uchunk goes to zero

Message ID 20240222092119.5602-1-gaoshanliukou@163.com
State New
Headers
Series [V3] kexec: copy only happens before uchunk goes to zero |

Commit Message

yang.zhang Feb. 22, 2024, 9:21 a.m. UTC 
  From: "yang.zhang" <yang.zhang@hexintek.com>

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.

Acked-by: Baoquan He <bhe@redhat.com>
Signed-off-by: yang.zhang <yang.zhang@hexintek.com>

---
V2 -> V3:
- Add more detailed description in the commit message
v1 -> v2:
- Only copy before uchunk goes to zero

V1: https://lore.kernel.org/lkml/20240130101802.23850-1-gaoshanliukou@163.com/
---
 kernel/kexec_core.c | 44 ++++++++++++++++++++++++--------------------
 1 file changed, 24 insertions(+), 20 deletions(-)

Comments

Baoquan He March 1, 2024, 6:52 a.m. UTC | #1 
CC Andrew

On 02/22/24 at 05:21pm, yang.zhang wrote:
> From: "yang.zhang" <yang.zhang@hexintek.com>
> 
> 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.
> 
> Acked-by: Baoquan He <bhe@redhat.com>
> Signed-off-by: yang.zhang <yang.zhang@hexintek.com>
> 
> ---
> V2 -> V3:
> - Add more detailed description in the commit message
> v1 -> v2:
> - Only copy before uchunk goes to zero
> 
> V1: https://lore.kernel.org/lkml/20240130101802.23850-1-gaoshanliukou@163.com/
> ---
>  kernel/kexec_core.c | 44 ++++++++++++++++++++++++--------------------
>  1 file changed, 24 insertions(+), 20 deletions(-)
> 
> diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
> index d08fc7b5db97..2fc3d0e3715a 100644
> --- a/kernel/kexec_core.c
> +++ b/kernel/kexec_core.c
> @@ -800,22 +800,24 @@ static int kimage_load_normal_segment(struct kimage *image,
>  				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();
> @@ -866,11 +868,18 @@ static int kimage_load_crash_segment(struct kimage *image,
>  			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);
> @@ -878,12 +887,7 @@ static int kimage_load_crash_segment(struct kimage *image,
>  			result = -EFAULT;
>  			goto out;
>  		}
> -		ubytes -= uchunk;
>  		maddr  += mchunk;
> -		if (image->file_mode)
> -			kbuf += mchunk;
> -		else
> -			buf += mchunk;
>  		mbytes -= mchunk;
>  
>  		cond_resched();
> -- 
> 2.25.1
>
diff mbox series

Patch

diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index d08fc7b5db97..2fc3d0e3715a 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -800,22 +800,24 @@  static int kimage_load_normal_segment(struct kimage *image,
 				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();
@@ -866,11 +868,18 @@  static int kimage_load_crash_segment(struct kimage *image,
 			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);
@@ -878,12 +887,7 @@  static int kimage_load_crash_segment(struct kimage *image,
 			result = -EFAULT;
 			goto out;
 		}
-		ubytes -= uchunk;
 		maddr  += mchunk;
-		if (image->file_mode)
-			kbuf += mchunk;
-		else
-			buf += mchunk;
 		mbytes -= mchunk;
 
 		cond_resched();