2020-01-12 23:54:42

by Qais Yousef

Subject: [PATCH] sched/uclamp: reject negative values in cpu_uclamp_write

The check to ensure that the new written value into cpu.uclamp.{min,max}
is within range, [0:100], wasn't working because of the signed
comparison

7301 if (req.percent > UCLAMP_PERCENT_SCALE) {
7302 req.ret = -ERANGE;
7303 return req;
7304 }

Cast req.percent into u64 to force the comparison to be unsigned and
work as intended in capacity_from_percent().

Fixes: 2480c093130f ("sched/uclamp: Extend CPU's cgroup controller")
Signed-off-by: Qais Yousef <[email protected]>
---
kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 90e4b00ace89..e66b131e3aeb 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7254,7 +7254,7 @@ capacity_from_percent(char *buf)
&req.percent);
if (req.ret)
return req;
- if (req.percent > UCLAMP_PERCENT_SCALE) {
+ if ((u64)req.percent > UCLAMP_PERCENT_SCALE) {
req.ret = -ERANGE;
return req;
}
--
2.17.1

2020-01-14 21:11:14

by Qais Yousef

Subject: [PATCH v2] sched/uclamp: reject negative values in cpu_uclamp_write

The check to ensure that the new written value into cpu.uclamp.{min,max}
is within range, [0:100], wasn't working because of the signed
comparison

7301 if (req.percent > UCLAMP_PERCENT_SCALE) {
7302 req.ret = -ERANGE;
7303 return req;
7304 }

# echo -1 > cpu.uclamp.min
# cat cpu.uclamp.min
42949671.96

Cast req.percent into u64 to force the comparison to be unsigned and
work as intended in capacity_from_percent().

# echo -1 > cpu.uclamp.min
sh: write error: Numerical result out of range

Fixes: 2480c093130f ("sched/uclamp: Extend CPU's cgroup controller")
Signed-off-by: Qais Yousef <[email protected]>
---

Changes in v2:
- Improve the commit message as suggested by T. Zhou

kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 90e4b00ace89..e66b131e3aeb 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7254,7 +7254,7 @@ capacity_from_percent(char *buf)
&req.percent);
if (req.ret)
return req;
- if (req.percent > UCLAMP_PERCENT_SCALE) {
+ if ((u64)req.percent > UCLAMP_PERCENT_SCALE) {
req.ret = -ERANGE;
return req;
}
--
2.17.1

2020-01-29 11:35:20

by tip-bot2 for Alexey Makhalov

Subject: [tip: sched/core] sched/uclamp: Reject negative values in cpu_uclamp_write()

The following commit has been merged into the sched/core branch of tip:

Commit-ID: b562d140649966d4daedd0483a8fe59ad3bb465a
Gitweb: https://git.kernel.org/tip/b562d140649966d4daedd0483a8fe59ad3bb465a
Author: Qais Yousef <[email protected]>
AuthorDate: Tue, 14 Jan 2020 21:09:47
Committer: Ingo Molnar <[email protected]>
CommitterDate: Tue, 28 Jan 2020 21:36:56 +01:00

sched/uclamp: Reject negative values in cpu_uclamp_write()

The check to ensure that the new written value into cpu.uclamp.{min,max}
is within range, [0:100], wasn't working because of the signed
comparison

7301 if (req.percent > UCLAMP_PERCENT_SCALE) {
7302 req.ret = -ERANGE;
7303 return req;
7304 }

# echo -1 > cpu.uclamp.min
# cat cpu.uclamp.min
42949671.96

Cast req.percent into u64 to force the comparison to be unsigned and
work as intended in capacity_from_percent().

# echo -1 > cpu.uclamp.min
sh: write error: Numerical result out of range

Fixes: 2480c093130f ("sched/uclamp: Extend CPU's cgroup controller")
Signed-off-by: Qais Yousef <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Link: https://lkml.kernel.org/r/[email protected]
---
kernel/sched/core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4ff03c2..55b9a9c 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7264,7 +7264,7 @@ capacity_from_percent(char *buf)
&req.percent);
if (req.ret)
return req;
- if (req.percent > UCLAMP_PERCENT_SCALE) {
+ if ((u64)req.percent > UCLAMP_PERCENT_SCALE) {
req.ret = -ERANGE;
return req;
}