[PATCH v2 01/45] arm_mpam: Stop using uninitialized variables in __ris_msmon_read()

Ben Horgan
2025-12-19T18:12:06Z

Dan has reported two uses of uninitialized variables in __ris_msmon_read().
If an unknown monitor type is encountered then the local variable, now, is
used uninitialized. Fix this by returning early on error. If a non-mbwu
monitor is being read then the local variable, overflow, is not initialized
but still read. Initialize it to false as overflow is not relevant for csu
monitors.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202512091519.RBwiJcSq-lkp@intel.com/
Closes: https://lore.kernel.org/r/202512100547.N7QPYgfb-lkp@intel.com/
Signed-off-by: Ben Horgan <ben.horgan@arm.com>
---
drivers/resctrl/mpam_devices.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
index 0b5b158e1aaf..b495d5291868 100644
--- a/drivers/resctrl/mpam_devices.c
+++ b/drivers/resctrl/mpam_devices.c
@@ -1072,7 +1072,7 @@ static void __ris_msmon_read(void *arg)
u64 now;
bool nrdy = false;
bool config_mismatch;
- bool overflow;
+ bool overflow = false;
struct mon_read *m = arg;
struct mon_cfg *ctx = m->ctx;
bool reset_on_next_read = false;
@@ -1176,10 +1176,11 @@ static void __ris_msmon_read(void *arg)
}
mpam_mon_sel_unlock(msc);

- if (nrdy) {
+ if (nrdy)
m->err = -EBUSY;
+
+ if (m->err)
return;
- }

*m->val += now;
}
--
2.43.0