Re: [dm-devel] [BUG] BLKZEROOUT on dm-crypt container cause OOM / kernel panic

[Damien Le Moal <Damien.LeMoal@wdc.com>]

On Sun, 2017-08-13 at 22:47 -0400, Mikulas Patocka wrote:
> 
> On Wed, 9 Aug 2017, hch@lst.de wrote:
> 
> > Does commit 615d22a51c04856efe62af6e1d5b450aaf5cc2c0
> > "block: Fix __blkdev_issue_zeroout loop" fix the issue for you?
> > 
> > --
> > dm-devel mailing list
> > dm-devel@redhat.com
> > https://www.redhat.com/mailman/listinfo/dm-devel
> 
> I think that patch is incorrect. sector_t may be a 32-bit type and 
> nr_sects << 9 may overflow.
> 
> static unsigned int __blkdev_sectors_to_bio_pages(sector_t nr_sects)
> {
>        sector_t bytes = (nr_sects << 9) + PAGE_SIZE - 1;
> 
>        return min(bytes >> PAGE_SHIFT, (sector_t)BIO_MAX_PAGES);
> }
> 
> Mikulas

Mikulas,

Does the follwing patch fix the problem ?

From 947b3cf41e759b2b23f684e215e651d0c8037f88 Mon Sep 17 00:00:00 2001
From: Damien Le Moal <damien.lemoal@wdc.com>
Date: Mon, 14 Aug 2017 13:01:16 +0900
Subject: [PATCH] block: Fix __blkdev_sectors_to_bio_pages()

On 32bit systems where sector_t is a 32bits type, the calculation of
bytes may overflow. Use the u64 type for the local calculation to avoid
overflows.

Signed-off-by: Damien Le Moal <damien.lemoal@wdc.com>
---
 block/blk-lib.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 3fe0aec90597..ccf22dba21f0 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -269,9 +269,9 @@ static int __blkdev_issue_write_zeroes(struct block_device
*bdev,
  */
 static unsigned int __blkdev_sectors_to_bio_pages(sector_t nr_sects)
 {
-	sector_t bytes = (nr_sects << 9) + PAGE_SIZE - 1;
+	u64 bytes = ((u64)nr_sects << 9) + PAGE_SIZE - 1;
 
-	return min(bytes >> PAGE_SHIFT, (sector_t)BIO_MAX_PAGES);
+	return min(bytes >> PAGE_SHIFT, (u64)BIO_MAX_PAGES);
 }
 
 /**
-- 
2.13.4


-- 
Damien Le Moal
Western Digital