On 02/20/2018 08:26 PM, Kees Cook wrote: > On Tue, Feb 20, 2018 at 3:17 PM, Andrew Morton > <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: >> On Mon, 19 Feb 2018 11:53:50 -0500 Waiman Long <longman@xxxxxxxxxx> wrote: >> >>> Even with clamped sysctl parameters, it is still not that straight >>> forward to figure out the exact range of those parameters. One may >>> try to write extreme parameter values to see if they get clamped. >>> To make it easier, a warning with the expected range will now be >>> printed in the kernel ring buffer when a clamped sysctl parameter >>> receives an out of range value. >> This assumes that do_proc_dointvec_minmax_conv() and >> do_proc_douintvec_minmax_conv() are only ever called by privileged >> userspace. Because we mustn't give unprivileged applications a way to >> spam the kernel logs. >> >> That's presumably true in the case of the caller you just added, but I >> don't see what we can do to guarantee this in the future, so perhaps we >> should add some permission check to the pr_warn()? > How about pr_warn_ratelimited() instead? > > -Kees > My current thinking is to issue at most one warning per sysctl parameter as additional warning of the same kind does not provide additional information. -Longman
