The function max6620_read checks shared data (tach and target) for zero
before passing it to max6620_fan_tach_to_rpm, which uses it as a divisor.
These accesses are currently lockless. If the data changes to zero
between the check and the division, it causes a divide-by-zero error.
Explicitly acquire the update lock around these checks and calculations
to ensure the data remains stable, preventing Time-of-Check to
Time-of-Use (TOCTOU) race conditions.
This change also aligns the locking behavior with the hwmon_fan_alarm
case, which already uses the update lock.
Link: https://lore.kernel.org/all/CALbr=LYJ_ehtp53HXEVkSpYoub+XYSTU8Rg=o1xxMJ8=5z…
Fixes: e8ac01e5db32 ("hwmon: Add Maxim MAX6620 hardware monitoring driver")
Cc: stable(a)vger.kernel.org
Signed-off-by: Gui-Dong Han <hanguidong02(a)gmail.com>
---
Based on the discussion in the link, I will submit a series of patches to
address TOCTOU issues in the hwmon subsystem by converting macros to
functions or adjusting locking where appropriate.
---
drivers/hwmon/max6620.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/hwmon/max6620.c b/drivers/hwmon/max6620.c
index 13201fb755c9..0dce2f5cb61b 100644
--- a/drivers/hwmon/max6620.c
+++ b/drivers/hwmon/max6620.c
@@ -290,20 +290,24 @@ max6620_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
*val = max6620_fan_div_from_reg(data->fandyn[channel]);
break;
case hwmon_fan_input:
+ mutex_lock(&data->update_lock);
if (data->tach[channel] == 0) {
*val = 0;
} else {
div = max6620_fan_div_from_reg(data->fandyn[channel]);
*val = max6620_fan_tach_to_rpm(div, data->tach[channel]);
}
+ mutex_unlock(&data->update_lock);
break;
case hwmon_fan_target:
+ mutex_lock(&data->update_lock);
if (data->target[channel] == 0) {
*val = 0;
} else {
div = max6620_fan_div_from_reg(data->fandyn[channel]);
*val = max6620_fan_tach_to_rpm(div, data->target[channel]);
}
+ mutex_unlock(&data->update_lock);
break;
default:
return -EOPNOTSUPP;
--
2.43.0
The patch titled
Subject: idr: fix idr_alloc() returning an ID out of range
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
idr-fix-idr_alloc-returning-an-id-out-of-range.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patche…
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy(a)infradead.org>
Subject: idr: fix idr_alloc() returning an ID out of range
Date: Fri, 28 Nov 2025 16:18:32 +0000
If you use an IDR with a non-zero base, and specify a range that lies
entirely below the base, 'max - base' becomes very large and
idr_get_free() can return an ID that lies outside of the requested range.
Link: https://lkml.kernel.org/r/20251128161853.3200058-1-willy@infradead.org
Fixes: 6ce711f27500 (idr: Make 1-based IDRs more efficient)
Signed-off-by: Matthew Wilcox (Oracle) <willy(a)infradead.org>
Reported-by: Jan Sokolowski <jan.sokolowski(a)intel.com>
Reported-by: Koen Koning koen.koning(a)intel.com
Reported-by: Peter Senna Tschudin peter.senna(a)linux.intel.com
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6449
Reviewed-by: Christian K��nig <christian.koenig(a)amd.com>
Cc: <stable(a)vger.kernel.org>
Signed-off-by: Andrew Morton <akpm(a)linux-foundation.org>
---
lib/idr.c | 2 ++
tools/testing/radix-tree/idr-test.c | 21 +++++++++++++++++++++
2 files changed, 23 insertions(+)
--- a/lib/idr.c~idr-fix-idr_alloc-returning-an-id-out-of-range
+++ a/lib/idr.c
@@ -40,6 +40,8 @@ int idr_alloc_u32(struct idr *idr, void
if (WARN_ON_ONCE(!(idr->idr_rt.xa_flags & ROOT_IS_IDR)))
idr->idr_rt.xa_flags |= IDR_RT_MARKER;
+ if (max < base)
+ return -ENOSPC;
id = (id < base) ? 0 : id - base;
radix_tree_iter_init(&iter, id);
--- a/tools/testing/radix-tree/idr-test.c~idr-fix-idr_alloc-returning-an-id-out-of-range
+++ a/tools/testing/radix-tree/idr-test.c
@@ -57,6 +57,26 @@ void idr_alloc_test(void)
idr_destroy(&idr);
}
+void idr_alloc2_test(void)
+{
+ int id;
+ struct idr idr = IDR_INIT_BASE(idr, 1);
+
+ id = idr_alloc(&idr, idr_alloc2_test, 0, 1, GFP_KERNEL);
+ assert(id == -ENOSPC);
+
+ id = idr_alloc(&idr, idr_alloc2_test, 1, 2, GFP_KERNEL);
+ assert(id == 1);
+
+ id = idr_alloc(&idr, idr_alloc2_test, 0, 1, GFP_KERNEL);
+ assert(id == -ENOSPC);
+
+ id = idr_alloc(&idr, idr_alloc2_test, 0, 2, GFP_KERNEL);
+ assert(id == -ENOSPC);
+
+ idr_destroy(&idr);
+}
+
void idr_replace_test(void)
{
DEFINE_IDR(idr);
@@ -409,6 +429,7 @@ void idr_checks(void)
idr_replace_test();
idr_alloc_test();
+ idr_alloc2_test();
idr_null_test();
idr_nowait_test();
idr_get_next_test(0);
_
Patches currently in -mm which might be from willy(a)infradead.org are
idr-fix-idr_alloc-returning-an-id-out-of-range.patch
mm-fix-vma_start_write_killable-signal-handling.patch
In max16065_current_show, data->curr_sense is read twice: once for the
error check and again for the calculation. Since
i2c_smbus_read_byte_data returns negative error codes on failure, if the
data changes to an error code between the check and the use, ADC_TO_CURR
results in an incorrect calculation.
Read data->curr_sense into a local variable to ensure consistency. Note
that data->curr_gain is constant and safe to access directly.
This aligns max16065_current_show with max16065_input_show, which
already uses a local variable for the same reason.
Link: https://lore.kernel.org/all/CALbr=LYJ_ehtp53HXEVkSpYoub+XYSTU8Rg=o1xxMJ8=5z…
Fixes: f5bae2642e3d ("hwmon: Driver for MAX16065 System Manager and compatibles")
Cc: stable(a)vger.kernel.org
Signed-off-by: Gui-Dong Han <hanguidong02(a)gmail.com>
---
Based on the discussion in the link, I will submit a series of patches to
address TOCTOU issues in the hwmon subsystem by converting macros to
functions or adjusting locking where appropriate.
---
drivers/hwmon/max16065.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/hwmon/max16065.c b/drivers/hwmon/max16065.c
index 0ccb5eb596fc..4c9e7892a73c 100644
--- a/drivers/hwmon/max16065.c
+++ b/drivers/hwmon/max16065.c
@@ -216,12 +216,13 @@ static ssize_t max16065_current_show(struct device *dev,
struct device_attribute *da, char *buf)
{
struct max16065_data *data = max16065_update_device(dev);
+ int curr_sense = data->curr_sense;
- if (unlikely(data->curr_sense < 0))
- return data->curr_sense;
+ if (unlikely(curr_sense < 0))
+ return curr_sense;
return sysfs_emit(buf, "%d\n",
- ADC_TO_CURR(data->curr_sense, data->curr_gain));
+ ADC_TO_CURR(curr_sense, data->curr_gain));
}
static ssize_t max16065_limit_store(struct device *dev,
--
2.43.0