From: Minchan Kim <minchan@xxxxxxxxxx>
Subject: 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.
Acutaully, 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.
Fixes: 42e99bd ("zram: optimize memory operations with clear_page()/copy_page()")
Link: http://lkml.kernel.org/r/1492042622-12074-2-git-send-email-minchan@xxxxxxxxxx
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/zram/zram_drv.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff -puN drivers/block/zram/zram_drv.c~zram-do-not-use-copy_page-with-non-page-alinged-address drivers/block/zram/zram_drv.c
--- a/drivers/block/zram/zram_drv.c~zram-do-not-use-copy_page-with-non-page-alinged-address
+++ a/drivers/block/zram/zram_drv.c
@@ -523,7 +523,7 @@ static int zram_decompress_page(struct z
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 @@ compress_again:
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);
_
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