From: Ben Horgan <ben.horgan@arm.com>
Date: Fri, 19 Dec 2025 18:11:03 +0000 (+0000)
Subject: arm_mpam: Stop using uninitialized variables in __ris_msmon_read()
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c2803bd580db226008aabf2fb2f0c9a7d3b5d0de;p=thirdparty%2Fkernel%2Flinux.git

arm_mpam: Stop using uninitialized variables in __ris_msmon_read()

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.

Fixes: 823e7c3712c5 ("arm_mpam: Add mpam_msmon_read() to read monitor value")
Fixes: 9e5afb7c3283 ("arm_mpam: Use long MBWU counters if supported")
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>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---

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;
 }