FAILED: patch "[PATCH] zram: do not use copy_page with non-page aligned address" failed to apply to 4.4-stable tree

The patch below does not apply to the 4.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From: Minchan Kim <[email protected]>
Date: Thu, 13 Apr 2017 14:56:37 -0700
Subject: [PATCH] zram: do not use copy_page with non-page aligned address

The copy_page is optimized memcpy for page-alinged address. If it is used with non-page aligned address, it can corrupt memory which means system corruption. With zram, it can happen with

1. 64K architecture
2. partial IO
3. slub debug

Partial IO need to allocate a page and zram allocates it via kmalloc. With slub debug, kmalloc(PAGE_SIZE) doesn't return page-size aligned address. And finally, copy_page(mem, cmem) corrupts memory.

So, this patch changes it to memcpy.

Actuaully, we don't need to change zram_bvec_write part because zsmalloc returns page-aligned address in case of PAGE_SIZE class but it's not good to rely on the internal of zsmalloc.

Note:
When this patch is merged to stable, clear_page should be fixed, too. Unfortunately, recent zram removes it by "same page merge" feature so it's hard to backport this patch to -stable tree.

I will handle it when I receive the mail from stable tree maintainer to merge this patch to backport.

index 03a7408e090d..0c09d4256108 100644
@@ -523,7 +523,7 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
 
 	cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
 	if (size == PAGE_SIZE) {
-		copy_page(mem, cmem);
+		memcpy(mem, cmem, PAGE_SIZE);
 	} else {
 		struct zcomp_strm *zstrm = zcomp_stream_get(zram->comp);
 

@@ -717,7 +717,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 
 	if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
 		src = kmap_atomic(page);
-		copy_page(cmem, src);
+		memcpy(cmem, src, PAGE_SIZE);
 		kunmap_atomic(src);
 	} else {
 		memcpy(cmem, src, clen);

Hi Greg,

I backported this patch against on stable-v4.4.61. I hope to merge this. Sergey, Could you review this?

Thanks.

From: Minchan Kim <[email protected]>
Date: Wed, 19 Apr 2017 09:28:39 +0900
Subject: [PATCH for v4.4] zram: do not use copy_page with non-page aligned address

commit d72e9a7a93e4f8e9e52491921d99e0c8aa89eb4e upstream

The copy_page is optimized memcpy for page-alinged address. If it is used with non-page aligned address, it can corrupt memory which means system corruption. With zram, it can happen with

1. 64K architecture
2. partial IO
3. slub debug

Partial IO need to allocate a page and zram allocates it via kmalloc. With slub debug, kmalloc(PAGE_SIZE) doesn't return page-size aligned address. And finally, copy_page(mem, cmem) corrupts memory.

So, this patch changes it to memcpy/memset.

Actuaully, we don't need to change zram_bvec_write part because zsmalloc returns page-aligned address in case of PAGE_SIZE class but it's not good to rely on the internal of zsmalloc.

And I didn't change clear_page in handle_zero_page intentionally because it's very clear no problem because kmap_atomic guarantees address is page-size alinged.

---
 drivers/block/zram/zram_drv.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

index 1648de80e230..62a93b685c54 100644
@@ -574,13 +574,13 @@ static int zram_decompress_page(struct zram *zram, char *mem, u32 index)
 
 	if (!handle || zram_test_flag(meta, index, ZRAM_ZERO)) {
 		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
-		clear_page(mem);
+		memset(mem, 0, PAGE_SIZE);
 		return 0;
 	}
 
 	cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_RO);
 	if (size == PAGE_SIZE)
-		copy_page(mem, cmem);
+		memcpy(mem, cmem, PAGE_SIZE);
 	else
 		ret = zcomp_decompress(zram->comp, cmem, size, mem);
 	zs_unmap_object(meta->mem_pool, handle);

@@ -738,7 +738,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
 
 	if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
 		src = kmap_atomic(page);
-		copy_page(cmem, src);
+		memcpy(cmem, src, PAGE_SIZE);
 		kunmap_atomic(src);
 	} else {
 		memcpy(cmem, src, clen);

2.7.4

Now merged, thanks!

greg k-h