linux-kernel - [PATCH] Input: avoid calling input_set_abs

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Message-ID: <ZFBg379uuHjf+YEM@google.com>
Date:   Mon, 1 May 2023 18:01:19 -0700
From:   Dmitry Torokhov <dmitry.torokhov@...il.com>
To:     linux-input@...r.kernel.org
Cc:     Teng Qi <starmiku1207184332@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH] Input: avoid calling input_set_abs_val() in the event
 handling core

input_abs_set_val() can nominally call input_alloc_absinfo() which may
allocate memory with GFP_KERNEL flag. This does not happen when
input_abs_set_val() is called by the input core to set current MT slot when
handling a new input event, but it trips certain static analyzers.

Rearrange the code to access the relevant structures directly.

Reported-by: Teng Qi <starmiku1207184332@...il.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---
 drivers/input/input.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/input/input.c b/drivers/input/input.c
index 37e876d45eb9..f791d14ecf23 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -190,6 +190,7 @@ static int input_handle_abs_event(struct input_dev *dev,
 				  unsigned int code, int *pval)
 {
 	struct input_mt *mt = dev->mt;
+	bool is_new_slot = false;
 	bool is_mt_event;
 	int *pold;
 
@@ -210,6 +211,7 @@ static int input_handle_abs_event(struct input_dev *dev,
 		pold = &dev->absinfo[code].value;
 	} else if (mt) {
 		pold = &mt->slots[mt->slot].abs[code - ABS_MT_FIRST];
+		is_new_slot = mt->slot != dev->absinfo[ABS_MT_SLOT].value;
 	} else {
 		/*
 		 * Bypass filtering for multi-touch events when
@@ -228,8 +230,8 @@ static int input_handle_abs_event(struct input_dev *dev,
 	}
 
 	/* Flush pending "slot" event */
-	if (is_mt_event && mt && mt->slot != input_abs_get_val(dev, ABS_MT_SLOT)) {
-		input_abs_set_val(dev, ABS_MT_SLOT, mt->slot);
+	if (is_new_slot) {
+		dev->absinfo[ABS_MT_SLOT].value = mt->slot;
 		return INPUT_PASS_TO_HANDLERS | INPUT_SLOT;
 	}
 
-- 
2.40.1.495.gc816e09b53d-goog


-- 
Dmitry