linux-kernel - [PATCH] input: tablet: aiptek: fix possible buffer overflow caused by bad DMA value in aiptek

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Date:   Sat, 30 May 2020 15:39:35 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     dmitry.torokhov@...il.com, johan@...nel.org, vdronov@...hat.com,
        tglx@...utronix.de, gregkh@...uxfoundation.org
Cc:     linux-input@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH] input: tablet: aiptek: fix possible buffer overflow caused by bad DMA value in aiptek_irq()

The value aiptek->data is stored in DMA memory, and it is assigned to
data. Thus in the code:
  macro = get_unaligned_le16(data + 1);
The value of marco can be modified by malicious hardware.
In this case, buffer overflow may occur when the code
"macroKeyEvents[macro - 1]" and "macroKeyEvents[macro]" is executed.

To fix these possible bugs, macro is checked before being used.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 drivers/input/tablet/aiptek.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/input/tablet/aiptek.c b/drivers/input/tablet/aiptek.c
index e08b0ef078e8..e353e538fb51 100644
--- a/drivers/input/tablet/aiptek.c
+++ b/drivers/input/tablet/aiptek.c
@@ -737,11 +737,11 @@ static void aiptek_irq(struct urb *urb)
 	 */
 	else if (data[0] == 6) {
 		macro = get_unaligned_le16(data + 1);
-		if (macro > 0) {
+		if (macro > 0 && macro < 34) {
 			input_report_key(inputdev, macroKeyEvents[macro - 1],
 					 0);
 		}
-		if (macro < 25) {
+		if (marco > 0 && macro < 25) {
 			input_report_key(inputdev, macroKeyEvents[macro + 1],
 					 0);
 		}
@@ -760,7 +760,8 @@ static void aiptek_irq(struct urb *urb)
 				aiptek->curSetting.toolMode;
 		}
 
-		input_report_key(inputdev, macroKeyEvents[macro], 1);
+		if (macro > 0 && macro < 33)
+			input_report_key(inputdev, macroKeyEvents[macro], 1);
 		input_report_abs(inputdev, ABS_MISC,
 				 1 | AIPTEK_REPORT_TOOL_UNKNOWN);
 		input_sync(inputdev);
-- 
2.17.1