From 0766e7317aab461889ae7fbb0da83fc70840f5ca Mon Sep 17 00:00:00 2001
From: Cyril Hrubis <chrubis@suse.cz>
Date: Mon, 2 Oct 2023 13:55:51 +0200
Subject: [PATCH] sched/rt: Disallow writing invalid values to
sched_rt_period_us
Patch-mainline: v6.7-rc1
Git-commit: 079be8fc630943d9fc70a97807feb73d169ee3fc
References: bsc#1220176
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@suse.cz/
Signed-off-by: Cyril Hrubis <chrubis@suse.cz>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20231002115553.3007-2-chrubis@suse.cz
[ pvorel: rebased for 5.15, 5.10 ]
[ pvorel: backported 0766e7317aab461889ae7fbb0da83fc70840f5ca from stable-5.15.150 ]
Reviewed-by: Petr Vorel <pvorel@suse.cz>
Signed-off-by: Petr Vorel <pvorel@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/sched/rt.c | 5 +----
kernel/sysctl.c | 4 ++++
2 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index b05684202b20..5fc99dce5145 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -2806,9 +2806,6 @@ static int sched_rt_global_constraints(void)
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 *
@@ -2839,7 +2836,7 @@ 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();
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 928798f89ca1..4554e80c4272 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -1821,6 +1821,8 @@ 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",
@@ -1828,6 +1830,8 @@ static struct ctl_table kern_table[] = {
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = sched_rt_handler,
+ .extra1 = SYSCTL_NEG_ONE,
+ .extra2 = SYSCTL_INT_MAX,
},
{
.procname = "sched_deadline_period_max_us",
--
2.35.3