linux-kernel - [PATCH] regulator: core: correct convergence check in regulator_set

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250729-b4-regulator-stepping-fix-v1-1-3f7b8c55d7d7@bootlin.com>
Date: Tue, 29 Jul 2025 11:50:57 +0200
From: Romain Gantois <romain.gantois@...tlin.com>
To: Liam Girdwood <lgirdwood@...il.com>, Mark Brown <broonie@...nel.org>
Cc: Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 linux-kernel@...r.kernel.org, Jon Hunter <jonathanh@...dia.com>, 
 Romain Gantois <romain.gantois@...tlin.com>
Subject: [PATCH] regulator: core: correct convergence check in
 regulator_set_voltage()

The logic in regulator_set_voltage() which checks for a non-convergence
condition on a stepped regulator is flawed.

regulator_set_voltage() checks if the error in target voltage has increased
or decreased, and returns -EWOULDBLOCK if the error has not decreased
enough. The correct non-convergence condition is:

new_delta - delta > -rdev->constraints->max_uV_step

or equivalently:

delta - new_delta < rdev->constraints->max_uV_step

But the currently used condition is:

new_delta - delta > rdev->constraints->max_uV_step

Which may cause an infinite loop if the voltage error doesn't converge.

Fix this by correcting the convergence condition.

Suggested-by: Jon Hunter <jonathanh@...dia.com>
Fixes: d511206dc7443 ("regulator: core: repeat voltage setting request for stepped regulators")
Signed-off-by: Romain Gantois <romain.gantois@...tlin.com>
---
 drivers/regulator/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 8ed9b96518cf5186c0db147a6895a92bc59fae4e..554d83c4af0c1c98edb43b60dbfacb8844d5e1eb 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -3884,7 +3884,7 @@ static int regulator_set_voltage_unlocked(struct regulator *regulator,
 			new_delta = ret;
 
 			/* check that voltage is converging quickly enough */
-			if (new_delta - delta > rdev->constraints->max_uV_step) {
+			if (delta - new_delta < rdev->constraints->max_uV_step) {
 				ret = -EWOULDBLOCK;
 				goto out;
 			}

---
base-commit: 0bd042ae771d61ef7ccd5882f7aeca59a25f71d9
change-id: 20250729-b4-regulator-stepping-fix-6e23fe03e914

Best regards,
-- 
Romain Gantois <romain.gantois@...tlin.com>