On Mon, 14 Aug 2017, Damien Le Moal wrote: > On Sun, 2017-08-13 at 22:47 -0400, Mikulas Patocka wrote: > > > > On Wed, 9 Aug 2017, hch@xxxxxx wrote: > > > > > Does commit 615d22a51c04856efe62af6e1d5b450aaf5cc2c0 > > > "block: Fix __blkdev_issue_zeroout loop" fix the issue for you? > > > > > > -- > > > dm-devel mailing list > > > dm-devel@xxxxxxxxxx > > > 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@xxxxxxx> > 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@xxxxxxx> > --- > 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); > } > It's OK, but it is not needed to use 64-bit arithmetic here if all we need is to shift the value right. Here I submit a simplified patch, using the macro DIV_ROUND_UP_SECTOR_T (the macro gets optimized to just an addition and right shift). From: Mikulas Patocka <mpatocka@xxxxxxxxxx> Fix possible integer overflow in __blkdev_sectors_to_bio_pages if sector_t is 32-bit. Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> Fixes: 615d22a51c04 ("block: Fix __blkdev_issue_zeroout loop") --- block/blk-lib.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) Index: linux-2.6/block/blk-lib.c =================================================================== --- linux-2.6.orig/block/blk-lib.c +++ linux-2.6/block/blk-lib.c @@ -269,9 +269,9 @@ static int __blkdev_issue_write_zeroes(s */ static unsigned int __blkdev_sectors_to_bio_pages(sector_t nr_sects) { - sector_t bytes = (nr_sects << 9) + PAGE_SIZE - 1; + sector_t pages = DIV_ROUND_UP_SECTOR_T(nr_sects, PAGE_SIZE / 512); - return min(bytes >> PAGE_SHIFT, (sector_t)BIO_MAX_PAGES); + return min(pages, (sector_t)BIO_MAX_PAGES); } /** -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
