On 8/15/17 09:01, Mikulas Patocka wrote: > > > 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); > } > > /** > Nice ! Thank you. Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxx> -- Damien Le Moal, Western Digital
