From: Cheng-Yu Lee <cylee12@realtek.com>

Previously, the address of the shared member '&map->spinlock_flags' was
passed directly to 'hwspin_lock_timeout_irqsave'. This creates a race
condition where multiple contexts contending for the lock could overwrite
the shared flags variable, potentially corrupting the state for the
current lock owner.

Fix this by using a local stack variable 'flags' to store the IRQ state
temporarily.

Fixes: 8698b9364710 ("regmap: Add hardware spinlock support")
Signed-off-by: Cheng-Yu Lee <cylee12@realtek.com>
Signed-off-by: Yu-Chun Lin <eleanor.lin@realtek.com>
---
 drivers/base/regmap/regmap.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/base/regmap/regmap.c b/drivers/base/regmap/regmap.c
index ce9be3989a21..8d889372517f 100644
--- a/drivers/base/regmap/regmap.c
+++ b/drivers/base/regmap/regmap.c
@@ -408,9 +408,11 @@ static void regmap_lock_hwlock_irq(void *__map)
 static void regmap_lock_hwlock_irqsave(void *__map)
 {
 	struct regmap *map = __map;
+	unsigned long flags;
 
 	hwspin_lock_timeout_irqsave(map->hwlock, UINT_MAX,
-				    &map->spinlock_flags);
+				    &flags);
+	map->spinlock_flags = flags;
 }
 
 static void regmap_unlock_hwlock(void *__map)
-- 
2.34.1

On Tue, 06 Jan 2026 10:15:01 +0800, Yu-Chun Lin wrote:
> Previously, the address of the shared member '&map->spinlock_flags' was
> passed directly to 'hwspin_lock_timeout_irqsave'. This creates a race
> condition where multiple contexts contending for the lock could overwrite
> the shared flags variable, potentially corrupting the state for the
> current lock owner.
> 
> Fix this by using a local stack variable 'flags' to store the IRQ state
> temporarily.
> 
> [...]

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap.git for-next

Thanks!

[1/1] regmap: Fix race condition in hwspinlock irqsave routine
      commit: 4b58aac989c1e3fafb1c68a733811859df388250

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

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to this mail.

Thanks,
Mark

On Tue, Jan 06, 2026 at 10:15:01AM +0800, Yu-Chun Lin wrote:

>  static void regmap_lock_hwlock_irqsave(void *__map)
>  {
>  	struct regmap *map = __map;
> +	unsigned long flags;
>  
>  	hwspin_lock_timeout_irqsave(map->hwlock, UINT_MAX,
> -				    &map->spinlock_flags);
> +				    &flags);
> +	map->spinlock_flags = flags;

This breaks a -Werror build:

/build/stage/linux/drivers/base/regmap/regmap.c: In function ‘regmap_lock_hwlock_irqsave’:
/build/stage/linux/drivers/base/regmap/regmap.c:415:29: error: ‘flags’ is used uninitialized [-Werror=uninitialized]
  415 |         map->spinlock_flags = flags;
      |         ~~~~~~~~~~~~~~~~~~~~^~~~~~~
/build/stage/linux/drivers/base/regmap/regmap.c:411:23: note: ‘flags’ was declared here
  411 |         unsigned long flags;
      |                       ^~~~~