From: Cyril Hrubis chrubis@suse.cz

[ 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@...

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 Signed-off-by: Petr Vorel pvorel@suse.cz --- kernel/sched/rt.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index 904dd8534597..4ac36eb4cdee 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -37,6 +37,8 @@ static struct ctl_table sched_rt_sysctls[] = { .maxlen = sizeof(unsigned int), .mode = 0644, .proc_handler = sched_rt_handler, + .extra1 = SYSCTL_ONE, + .extra2 = SYSCTL_INT_MAX, }, { .procname = "sched_rt_runtime_us", @@ -44,6 +46,8 @@ static struct ctl_table sched_rt_sysctls[] = { .maxlen = sizeof(int), .mode = 0644, .proc_handler = sched_rt_handler, + .extra1 = SYSCTL_NEG_ONE, + .extra2 = SYSCTL_INT_MAX, }, { .procname = "sched_rr_timeslice_ms", @@ -2989,9 +2993,6 @@ 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 * @@ -3022,7 +3023,7 @@ 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();