On Tue, Jan 17, 2023 at 03:08:05PM +0800, Yu Kuai wrote: > From: Li Nan <linan122@xxxxxxxxxx> > > 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: > <TASK> > 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 <linan122@xxxxxxxxxx> > Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx> Acked-by: Tejun Heo <tj@xxxxxxxxxx> Thanks. -- tejun
