From 984af1e66b4126cf145153661cc24c213e2ec231 Mon Sep 17 00:00:00 2001 From: Li Nan Date: Tue, 17 Jan 2023 15:08:05 +0800 Subject: blk-iocost: fix divide by 0 error in calc_lcoefs() echo max of u64 to cost.model can cause divide by 0 error. # echo 8:0 rbps=18446744073709551615 > /sys/fs/cgroup/io.cost.model divide error: 0000 [#1] PREEMPT SMP RIP: 0010:calc_lcoefs+0x4c/0xc0 Call Trace: ioc_refresh_params+0x2b3/0x4f0 ioc_cost_model_write+0x3cb/0x4c0 ? _copy_from_iter+0x6d/0x6c0 ? kernfs_fop_write_iter+0xfc/0x270 cgroup_file_write+0xa0/0x200 kernfs_fop_write_iter+0x17d/0x270 vfs_write+0x414/0x620 ksys_write+0x73/0x160 __x64_sys_write+0x1e/0x30 do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x63/0xcd calc_lcoefs() uses the input value of cost.model in DIV_ROUND_UP_ULL, overflow would happen if bps plus IOC_PAGE_SIZE is greater than ULLONG_MAX, it can cause divide by 0 error. Fix the problem by setting basecost Signed-off-by: Li Nan Signed-off-by: Yu Kuai Acked-by: Tejun Heo Link: https://lore.kernel.org/r/20230117070806.3857142-5-yukuai1@huaweicloud.com Signed-off-by: Jens Axboe --- block/blk-iocost.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'block/blk-iocost.c') diff --git a/block/blk-iocost.c b/block/blk-iocost.c index 58ad4e5b2fff..a4f195685c3c 100644 --- a/block/blk-iocost.c +++ b/block/blk-iocost.c @@ -868,9 +868,14 @@ static void calc_lcoefs(u64 bps, u64 seqiops, u64 randiops, *page = *seqio = *randio = 0; - if (bps) - *page = DIV64_U64_ROUND_UP(VTIME_PER_SEC, - DIV_ROUND_UP_ULL(bps, IOC_PAGE_SIZE)); + if (bps) { + u64 bps_pages = DIV_ROUND_UP_ULL(bps, IOC_PAGE_SIZE); + + if (bps_pages) + *page = DIV64_U64_ROUND_UP(VTIME_PER_SEC, bps_pages); + else + *page = 1; + } if (seqiops) { v = DIV64_U64_ROUND_UP(VTIME_PER_SEC, seqiops); -- cgit v1.2.3