The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
Possible dependencies:
d501d37841d3 ("counter: 104-quad-8: Fix race getting function mode and direction") aea8334b24fe ("counter: 104-quad-8: Convert to counter_priv() wrapper") 7aa2ba0df651 ("counter: 104-quad-8: Add IRQ support for the ACCES 104-QUAD-8") 09db4678bfbb ("counter: 104-quad-8: Replace mutex with spinlock") aaec1a0f76ec ("counter: Internalize sysfs interface code") ea434ff82649 ("counter: stm32-timer-cnt: Provide defines for slave mode selection") 05593a3fd103 ("counter: stm32-lptimer-cnt: Provide defines for clock polarities") 394a0150a064 ("counter: Rename counter_count_function to counter_function") 493b938a14ed ("counter: Rename counter_signal_value to counter_signal_level") b11eed1554e8 ("counter: Return error code on invalid modes") 728246e8f726 ("counter: 104-quad-8: Return error when invalid mode during ceiling_write") d0ce3d5cf77d ("counter: stm32-timer-cnt: Add const qualifier for actions_list array") f83e6e59366b ("counter: stm32-lptimer-cnt: Add const qualifier for actions_list array") 0056a405c7ad ("counter: microchip-tcb-capture: Add const qualifier for actions_list array") 9b2574f61c49 ("counter: ftm-quaddec: Add const qualifier for actions_list array") 6a9eb0e31044 ("counter: 104-quad-8: Add const qualifier for actions_list array") 45af9ae84c60 ("counter: stm32-timer-cnt: Add const qualifier for functions_list array") 8a00fed665ad ("counter: stm32-lptimer-cnt: Add const qualifier for functions_list array") 7e0dcfcefeca ("counter: microchip-tcb-capture: Add const qualifier for functions_list array") 891b58b35fd6 ("counter: interrupt-cnt: Add const qualifier for functions_list array")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From d501d37841d3b7f18402d71a9ef057eb9dde127e Mon Sep 17 00:00:00 2001 From: William Breathitt Gray william.gray@linaro.org Date: Thu, 20 Oct 2022 10:11:21 -0400 Subject: [PATCH] counter: 104-quad-8: Fix race getting function mode and direction
The quad8_action_read() function checks the Count function mode and Count direction without first acquiring a lock. This is a race condition because the function mode could change by the time the direction is checked.
Because the quad8_function_read() already acquires a lock internally, the quad8_function_read() is refactored to spin out the no-lock code to a new quad8_function_get() function.
To resolve the race condition in quad8_action_read(), a lock is acquired before calling quad8_function_get() and quad8_direction_read() in order to get both function mode and direction atomically.
Fixes: f1d8a071d45b ("counter: 104-quad-8: Add Generic Counter interface support") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20221020141121.15434-1-william.gray@linaro.org/ Signed-off-by: William Breathitt Gray william.gray@linaro.org
diff --git a/drivers/counter/104-quad-8.c b/drivers/counter/104-quad-8.c index 77a863b7eefe..deed4afadb29 100644 --- a/drivers/counter/104-quad-8.c +++ b/drivers/counter/104-quad-8.c @@ -232,34 +232,45 @@ static const enum counter_function quad8_count_functions_list[] = { COUNTER_FUNCTION_QUADRATURE_X4, };
+static int quad8_function_get(const struct quad8 *const priv, const size_t id, + enum counter_function *const function) +{ + if (!priv->quadrature_mode[id]) { + *function = COUNTER_FUNCTION_PULSE_DIRECTION; + return 0; + } + + switch (priv->quadrature_scale[id]) { + case 0: + *function = COUNTER_FUNCTION_QUADRATURE_X1_A; + return 0; + case 1: + *function = COUNTER_FUNCTION_QUADRATURE_X2_A; + return 0; + case 2: + *function = COUNTER_FUNCTION_QUADRATURE_X4; + return 0; + default: + /* should never reach this path */ + return -EINVAL; + } +} + static int quad8_function_read(struct counter_device *counter, struct counter_count *count, enum counter_function *function) { struct quad8 *const priv = counter_priv(counter); - const int id = count->id; unsigned long irqflags; + int retval;
spin_lock_irqsave(&priv->lock, irqflags);
- if (priv->quadrature_mode[id]) - switch (priv->quadrature_scale[id]) { - case 0: - *function = COUNTER_FUNCTION_QUADRATURE_X1_A; - break; - case 1: - *function = COUNTER_FUNCTION_QUADRATURE_X2_A; - break; - case 2: - *function = COUNTER_FUNCTION_QUADRATURE_X4; - break; - } - else - *function = COUNTER_FUNCTION_PULSE_DIRECTION; + retval = quad8_function_get(priv, count->id, function);
spin_unlock_irqrestore(&priv->lock, irqflags);
- return 0; + return retval; }
static int quad8_function_write(struct counter_device *counter, @@ -359,6 +370,7 @@ static int quad8_action_read(struct counter_device *counter, enum counter_synapse_action *action) { struct quad8 *const priv = counter_priv(counter); + unsigned long irqflags; int err; enum counter_function function; const size_t signal_a_id = count->synapses[0].signal->id; @@ -374,9 +386,21 @@ static int quad8_action_read(struct counter_device *counter, return 0; }
- err = quad8_function_read(counter, count, &function); - if (err) + spin_lock_irqsave(&priv->lock, irqflags); + + /* Get Count function and direction atomically */ + err = quad8_function_get(priv, count->id, &function); + if (err) { + spin_unlock_irqrestore(&priv->lock, irqflags); + return err; + } + err = quad8_direction_read(counter, count, &direction); + if (err) { + spin_unlock_irqrestore(&priv->lock, irqflags); return err; + } + + spin_unlock_irqrestore(&priv->lock, irqflags);
/* Default action mode */ *action = COUNTER_SYNAPSE_ACTION_NONE; @@ -389,10 +413,6 @@ static int quad8_action_read(struct counter_device *counter, return 0; case COUNTER_FUNCTION_QUADRATURE_X1_A: if (synapse->signal->id == signal_a_id) { - err = quad8_direction_read(counter, count, &direction); - if (err) - return err; - if (direction == COUNTER_COUNT_DIRECTION_FORWARD) *action = COUNTER_SYNAPSE_ACTION_RISING_EDGE; else