This is a note to let you know that I've just added the patch titled
sched/rt: Disallow writing invalid values to sched_rt_period_us
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
sched-rt-disallow-writing-invalid-values-to-sched_rt_period_us.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 079be8fc630943d9fc70a97807feb73d169ee3fc Mon Sep 17 00:00:00 2001
From: Cyril Hrubis <chrubis@xxxxxxx>
Date: Mon, 2 Oct 2023 13:55:51 +0200
Subject: sched/rt: Disallow writing invalid values to sched_rt_period_us
From: Cyril Hrubis <chrubis@xxxxxxx>
commit 079be8fc630943d9fc70a97807feb73d169ee3fc upstream.
The validation of the value written to sched_rt_period_us was broken
because:
- the sysclt_sched_rt_period is declared as unsigned int
- parsed by proc_do_intvec()
- the range is asserted after the value parsed by proc_do_intvec()
Because of this negative values written to the file were written into a
unsigned integer that were later on interpreted as large positive
integers which did passed the check:
if (sysclt_sched_rt_period <= 0)
return EINVAL;
This commit fixes the parsing by setting explicit range for both
perid_us and runtime_us into the sched_rt_sysctls table and processes
the values with proc_dointvec_minmax() instead.
Alternatively if we wanted to use full range of unsigned int for the
period value we would have to split the proc_handler and use
proc_douintvec() for it however even the
Documentation/scheduller/sched-rt-group.rst describes the range as 1 to
INT_MAX.
As far as I can tell the only problem this causes is that the sysctl
file allows writing negative values which when read back may confuse
userspace.
There is also a LTP test being submitted for these sysctl files at:
http://patchwork.ozlabs.org/project/ltp/patch/20230901144433.2526-1-chrubis@xxxxxxx/
Signed-off-by: Cyril Hrubis <chrubis@xxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20231002115553.3007-2-chrubis@xxxxxxx
[ pvorel: rebased for 5.4 ]
Reviewed-by: Petr Vorel <pvorel@xxxxxxx>
Signed-off-by: Petr Vorel <pvorel@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
kernel/sched/rt.c | 5 +----
kernel/sysctl.c | 4 ++++
2 files changed, 5 insertions(+), 4 deletions(-)
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2659,9 +2659,6 @@ static int sched_rt_global_constraints(v
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 *
@@ -2693,7 +2690,7 @@ int sched_rt_handler(struct ctl_table *t
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();
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -465,6 +465,8 @@ static struct ctl_table kern_table[] = {
.maxlen = sizeof(unsigned int),
.mode = 0644,
.proc_handler = sched_rt_handler,
+ .extra1 = SYSCTL_ONE,
+ .extra2 = SYSCTL_INT_MAX,
},
{
.procname = "sched_rt_runtime_us",
@@ -472,6 +474,8 @@ static struct ctl_table kern_table[] = {
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = sched_rt_handler,
+ .extra1 = &neg_one,
+ .extra2 = SYSCTL_INT_MAX,
},
{
.procname = "sched_rr_timeslice_ms",
Patches currently in stable-queue which might be from chrubis@xxxxxxx are
queue-5.4/sched-rt-disallow-writing-invalid-values-to-sched_rt_period_us.patch
queue-5.4/sched-rt-fix-sysctl_sched_rr_timeslice-intial-value.patch
queue-5.4/sched-rt-sysctl_sched_rr_timeslice-show-default-timeslice-after-reset.patch
