On Sunday, November 1, 2020, Stefan Eßer <s...@freebsd.org> wrote:
> Author: se
> Date: Sat Oct 31 23:48:41 2020
> New Revision: 367243
> URL: https://svnweb.freebsd.org/changeset/base/367243
>
> Log:
> Make sysctl user.local a tunable that can be written at run-time
>
> This sysctl value had been provided as a read-only variable that is
> compiled into the C library based on the value of _PATH_LOCALBASE in
> paths.h.
>
> After this change, the value is compiled into the kernel as an empty
> string, which is translated to _PATH_LOCALBASE by the C library.
>
> This empty string can be overridden at boot time or by a privileged
> user at run time and will then be returned by sysctl.
>
> When set to an empty string, the value returned by sysctl reverts to
> _PATH_LOCALBASE.
>
> This update does not change the behavior on any system that does
> not modify the default value of user.localbase.
>
> I consider this change as experimental and would prefer if the run-time
> write permission was reconsidered and the sysctl variable defined with
> CLFLAG_RDTUN instead to restrict it to be set at boot time.
>
> MFC after: 1 month
Wouldn't be better to make this variable a per-jail variable?
>
> Modified:
> head/lib/libc/gen/sysctl.c
> head/sys/kern/kern_mib.c
>
> Modified: head/lib/libc/gen/sysctl.c
> ============================================================
> ==================
> --- head/lib/libc/gen/sysctl.c Sat Oct 31 23:19:59 2020 (r367242)
> +++ head/lib/libc/gen/sysctl.c Sat Oct 31 23:48:41 2020 (r367243)
> @@ -68,14 +68,14 @@ sysctl(const int *name, u_int namelen, void *oldp, siz
> if (retval || name[0] != CTL_USER)
> return (retval);
>
> - if (newp != NULL) {
> - errno = EPERM;
> - return (-1);
> - }
> if (namelen != 2) {
> errno = EINVAL;
> return (-1);
> }
> + if (newp != NULL && name[1] != USER_LOCALBASE) {
> + errno = EPERM;
> + return (-1);
> + }
>
> switch (name[1]) {
> case USER_CS_PATH:
> @@ -88,13 +88,21 @@ sysctl(const int *name, u_int namelen, void *oldp, siz
> memmove(oldp, _PATH_STDPATH,
> sizeof(_PATH_STDPATH));
> return (0);
> case USER_LOCALBASE:
> - if (oldp != NULL && orig_oldlen < sizeof(_PATH_LOCALBASE))
> {
> - errno = ENOMEM;
> - return (-1);
> + if (oldlenp != NULL) {
> + if (oldp == NULL) {
> + if (*oldlenp == 1)
> + *oldlenp = sizeof(_PATH_LOCALBASE);
> + } else {
> + if (*oldlenp != 1)
> + return (retval);
> + if (orig_oldlen < sizeof(_PATH_LOCALBASE))
> {
> + errno = ENOMEM;
> + return (-1);
> + }
> + *oldlenp = sizeof(_PATH_LOCALBASE);
> + memmove(oldp, _PATH_LOCALBASE,
> sizeof(_PATH_LOCALBASE));
> + }
> }
> - *oldlenp = sizeof(_PATH_LOCALBASE);
> - if (oldp != NULL)
> - memmove(oldp, _PATH_LOCALBASE,
> sizeof(_PATH_LOCALBASE));
> return (0);
> }
>
>
> Modified: head/sys/kern/kern_mib.c
> ============================================================
> ==================
> --- head/sys/kern/kern_mib.c Sat Oct 31 23:19:59 2020 (r367242)
> +++ head/sys/kern/kern_mib.c Sat Oct 31 23:48:41 2020 (r367243)
> @@ -652,8 +652,11 @@ SYSCTL_INT(_user, USER_STREAM_MAX, stream_max, CTLFLAG
> SYSCTL_NULL_INT_PTR, 0, "Min Maximum number of streams a process may
> have open at one time");
> SYSCTL_INT(_user, USER_TZNAME_MAX, tzname_max, CTLFLAG_RD,
> SYSCTL_NULL_INT_PTR, 0, "Min Maximum number of types supported for
> timezone names");
> -SYSCTL_STRING(_user, USER_LOCALBASE, localbase, CTLFLAG_RD,
> - "", 0, "Prefix used to install and locate add-on packages");
> +
> +static char localbase[MAXPATHLEN] = "";
> +
> +SYSCTL_STRING(_user, USER_LOCALBASE, localbase, CTLFLAG_RWTUN,
> + localbase, sizeof(localbase), "Prefix used to install and locate
> add-on packages");
>
> #include <sys/vnode.h>
> SYSCTL_INT(_debug_sizeof, OID_AUTO, vnode, CTLFLAG_RD,
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