4.19-stable review patch. If anyone has any objections, please let me know. ------------------ 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 4.19 ] 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 | 5 +++++ 2 files changed, 6 insertions(+), 4 deletions(-) --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -2658,9 +2658,6 @@ 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)) return -EINVAL; @@ -2690,7 +2687,7 @@ 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 @@ -127,6 +127,7 @@ static int zero; static int __maybe_unused one = 1; static int __maybe_unused two = 2; static int __maybe_unused four = 4; +static int int_max = INT_MAX; static unsigned long zero_ul; static unsigned long one_ul = 1; static unsigned long long_max = LONG_MAX; @@ -464,6 +465,8 @@ static struct ctl_table kern_table[] = { .maxlen = sizeof(unsigned int), .mode = 0644, .proc_handler = sched_rt_handler, + .extra1 = &one, + .extra2 = &int_max, }, { .procname = "sched_rt_runtime_us", @@ -471,6 +474,8 @@ static struct ctl_table kern_table[] = { .maxlen = sizeof(int), .mode = 0644, .proc_handler = sched_rt_handler, + .extra1 = &neg_one, + .extra2 = &int_max, }, { .procname = "sched_rr_timeslice_ms",
