From: Cyril Hrubis <chrubis@xxxxxxx> [ Upstream commit 079be8fc630943d9fc70a97807feb73d169ee3fc ] 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> --- 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 fea993827c4f..873f364cb3c6 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2659,9 +2659,6 @@ 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 * @@ -2693,7 +2690,7 @@ int sched_rt_handler(struct ctl_table *table, int write, 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 4f85f7ed42fc..865e539c7354 100644 --- 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", -- 2.35.3
