Messages in this thread Patch in this message | | | From | Valentin Schneider <> | Subject | Re: [PATCH v2] sched/rt: fix the case where sched_rt_period_us is negative | Date | Mon, 16 May 2022 16:04:48 +0100 |
| |
On 12/05/22 08:39, Yajun Deng wrote: > The proc_dointvec() is for integer, but sysctl_sched_rt_period is a > unsigned integer, proc_dointvec() would convert negative number into > positive number. So both proc_dointvec() and sched_rt_global_validate() > aren't return error even if we set a negative number. > > Use proc_dointvec_minmax() instead of proc_dointvec() and use extra1 > limit the minimum value for sched_rt_period_us/sched_rt_runtime_us. > > Fixes: 391e43da797a ("sched: Move all scheduler bits into kernel/sched/")
That's just the last apparent change of the incriminated variable. AFAICT the issue stems from:
- sysctl_sched_rt_period being unsigned int - the ctl entry using proc_dointvec() - the bounds check on sysctl_sched_rt_period being just <= 0 which doesn't actually respect the [1, INT_MAX] stated in Documentation/scheduler/sched-rt-group.rst
The <= thing was added by:
ec5d498991e8 ("sched: fix deadlock in setting scheduler parameter to zero")
but AFAICT the unsigned int vs proc_dointvec() thing dates back to:
d0b27fa77854 ("sched: rt-group: synchonised bandwidth period")
> Signed-off-by: Yajun Deng <yajun.deng@linux.dev> > ---
In the absence of a cover letter (e.g. single-patch submission), this is where you should write patch version changelogs (see Documentation/process).
> kernel/sched/rt.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > index b491a0f8c25d..3add32679885 100644 > --- a/kernel/sched/rt.c > +++ b/kernel/sched/rt.c > @@ -37,6 +37,7 @@ static struct ctl_table sched_rt_sysctls[] = { > .maxlen = sizeof(unsigned int), > .mode = 0644, > .proc_handler = sched_rt_handler, > + .extra1 = SYSCTL_ONE,
Per earlier comment, the Documentation says that this needs to be within [1, INT_MAX], which you do get by excluding negative values when casting to int...
How about we make sysctl_sched_rt_period int on top of this, then all variables modified by the sched_rt_handler() proc_dointvec() are *actually* int, and the upper bound requires less mental gymnastics to be figured out?
> }, > { > .procname = "sched_rt_runtime_us", > @@ -44,6 +45,8 @@ static struct ctl_table sched_rt_sysctls[] = { > .maxlen = sizeof(int), > .mode = 0644, > .proc_handler = sched_rt_handler, > + .extra1 = SYSCTL_NEG_ONE, > + .extra2 = (void *)&sysctl_sched_rt_period,
Per this, you could also remove the
((sysctl_sched_rt_runtime > sysctl_sched_rt_period) ||
from sched_rt_global_validate(), no?
> }, > { > .procname = "sched_rr_timeslice_ms", > @@ -2959,9 +2962,6 @@ static int sched_rt_global_constraints(void) > #ifdef CONFIG_SYSCTL > static int sched_rt_global_validate(void) > { > - if (sysctl_sched_rt_period <= 0) > - return -EINVAL; > - > if ((sysctl_sched_rt_runtime != RUNTIME_INF) && > ((sysctl_sched_rt_runtime > sysctl_sched_rt_period) || > ((u64)sysctl_sched_rt_runtime * > @@ -2992,7 +2992,7 @@ static int sched_rt_handler(struct ctl_table *table, int write, void *buffer, > old_period = sysctl_sched_rt_period; > old_runtime = sysctl_sched_rt_runtime; > > - ret = proc_dointvec(table, write, buffer, lenp, ppos); > + ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos); > > if (!ret && write) { > ret = sched_rt_global_validate(); > -- > 2.25.1
| |