On Thu, Apr 25, 2019 at 4:20 PM Pingfan Liu <kernelfans@xxxxxxxxx> wrote: > > On Wed, Apr 24, 2019 at 4:31 PM Matthias Brugger <mbrugger@xxxxxxxx> wrote: > > > > > [...] > > > @@ -139,6 +141,8 @@ static int __init parse_crashkernel_simple(char *cmdline, > > > pr_warn("crashkernel: unrecognized char: %c\n", *cur); > > > return -EINVAL; > > > } > > > + if (*crash_size == 0) > > > + return -EINVAL; > > > > This covers the case where I pass an argument like "crashkernel=0M" ? > > Can't we fix that by using kstrtoull() in memparse and check if the return value > > is < 0? In that case we could return without updating the retptr and we will be > > fine. After a series of work, I suddenly realized that it can not be done like this way. "0M" causes kstrtoull() to return -EINVAL, but this is caused by "M", not "0". If passing "0" to kstrtoull(), it will return 0 on success. > > > It seems that kstrtoull() treats 0M as invalid parameter, while > simple_strtoull() does not. > My careless going through the code. And I tested with a valid value "256M" using kstrtoull(), it also returned -EINVAL. So I think there is no way to distinguish 0 from a positive value inside this basic math function. Do I miss anything? Thanks and regards, Pingfan