Patch "zram: do not use copy_page with non-page aligned address" has been added to the 4.10-stable tree

PATCH [email protected] 2 participants 3 messages Apr 18, 2017 – Apr 19, 2017

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[email protected]

author maintainer Applied

2017-04-18 12:49 UTC #0 lore raw

This is a note to let you know that I've just added the patch titled

zram: do not use copy_page with non-page aligned address

to the 4.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
zram-do-not-use-copy_page-with-non-page-aligned-address.patch
and it can be found in the queue-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

Quoted 1 line

From d72e9a7a93e4f8e9e52491921d99e0c8aa89eb4e Mon Sep 17 00:00:00 2001

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

From: Minchan Kim <[email protected]>

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/[email protected] open here

Signed-off-by Minchan Kim <[email protected]>

Cc Sergey Senozhatsky <[email protected]>

Signed-off-by Andrew Morton <[email protected]>

Signed-off-by Linus Torvalds <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 drivers/block/zram/zram_drv.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

drivers/block/zram/zram_drv.c +2 -2

@@ -589,7 +589,7 @@ 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);

@@ -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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.10/zram-do-not-use-copy_page-with-non-page-aligned-address.patch queue-4.10/zram-fix-operator-precedence-to-get-offset.patch queue-4.10/thp-fix-madv_dontneed-vs.-madv_free-race.patch queue-4.10/zsmalloc-expand-class-bit.patch

Minchan Kim

maintainer

2017-04-19 00:54 UTC #1 lore raw

Hello Greg,

Quoted 43 lines · On Tue, Apr 18, 2017 at 02:49:12PM +0200, [email protected] wrote:

This is a note to let you know that I've just added the patch titled
zram: do not use copy_page with non-page aligned address
to the 4.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
zram-do-not-use-copy_page-with-non-page-aligned-address.patch
and it can be found in the queue-4.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
From d72e9a7a93e4f8e9e52491921d99e0c8aa89eb4e Mon Sep 17 00:00:00 2001
From: Minchan Kim <[email protected]>
Date: Thu, 13 Apr 2017 14:56:37 -0700
Subject: zram: do not use copy_page with non-page aligned address
From: Minchan Kim <[email protected]>
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.

Quoted 8 lines

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.

By above reason, I wanted to send new version to cover clear_page part when I receive this mail.
Could you merge below patch, instead?

Thanks.

Quoted 1 line

From 45ff3faa88d372707bed450593193085a1511e25 Mon Sep 17 00:00:00 2001

From: Minchan Kim <[email protected]>
Date: Thu, 13 Apr 2017 14:56:37 -0700
Subject: [PATCH for v4.10] 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|clear]_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.

Cc Sergey Senozhatsky <[email protected]>

Cc <[email protected]>

Cc Andrew Morton <[email protected]>

Fixes 42e99bd ("zram: optimize memory operations with clear_page()/copy_page()")

Link http://lkml.kernel.org/r/[email protected] open here

Signed-off-by Minchan Kim <[email protected]>

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

drivers/block/zram/zram_drv.c +3 -3

index e5ab7d9e8c45..5b4b59be8b1f 100644
@@ -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 @@ 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);

Signature · 1 line

2.7.4

Greg KH

author maintainer

2017-04-19 11:36 UTC #2 lore raw

Quoted 51 lines · Minchan Kim

Hello Greg,
Quoted 48 lines · On Tue, Apr 18, 2017 at 02:49:12PM +0200, [email protected] wrote:
This is a note to let you know that I've just added the patch titled
zram: do not use copy_page with non-page aligned address
to the 4.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
zram-do-not-use-copy_page-with-non-page-aligned-address.patch
and it can be found in the queue-4.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
From d72e9a7a93e4f8e9e52491921d99e0c8aa89eb4e Mon Sep 17 00:00:00 2001
From: Minchan Kim <[email protected]>
Date: Thu, 13 Apr 2017 14:56:37 -0700
Subject: zram: do not use copy_page with non-page aligned address
From: Minchan Kim <[email protected]>
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.

Quoted 7 lines

Quoted 3 lines
I will handle it when I receive the mail from stable tree maintainer to merge this patch to backport.
By above reason, I wanted to send new version to cover clear_page part when I receive this mail.
Could you merge below patch, instead?

Now replaced, thanks.

greg k-h