From 58bc856c41fb7e986f6bcc70107d5f7efa529d3b Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Thu, 13 Apr 2017 14:56:37 -0700 Subject: [PATCH] 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. 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. Fixes: 42e99bd ("zram: optimize memory operations with clear_page()/copy_page()") Link: http://lkml.kernel.org/r/1492042622-12074-2-git-send-email-minchan@kernel.org Signed-off-by: Minchan Kim Cc: Sergey Senozhatsky Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- drivers/block/zram/zram_drv.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index e5ab7d9e8c452..5b4b59be8b1f4 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -583,13 +583,13 @@ 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 { struct zcomp_strm *zstrm = zcomp_stream_get(zram->comp); @@ -781,7 +781,7 @@ 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); -- 2.47.2