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From:   Gabriel Ravier <gabravier@gmail.com>
To:     linus.walleij@linaro.org, bgolaszewski@baylibre.com
Cc:     linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org,
        Gabriel Ravier <gabravier@gmail.com>
Subject: [PATCH] gpio-hammer: Avoid potential overflow in main
Date:   Thu, 12 Mar 2020 10:40:08 +0100
Message-Id: <20200312094008.1833929-1-gabravier@gmail.com>
MIME-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

If '-o' was used more than 64 times in a single invocation of gpio-hammer,
this could lead to an overflow of the 'lines' array. This commit fixes
this by avoiding the overflow and giving a proper diagnostic back to the
user

Signed-off-by: Gabriel Ravier <gabravier@gmail.com>
---
 tools/gpio/gpio-hammer.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/tools/gpio/gpio-hammer.c b/tools/gpio/gpio-hammer.c
index 0e0060a6e..273d33847 100644
--- a/tools/gpio/gpio-hammer.c
+++ b/tools/gpio/gpio-hammer.c
@@ -77,7 +77,7 @@ int hammer_device(const char *device_name, unsigned int *lines, int nlines,
 
 		fprintf(stdout, "[%c] ", swirr[j]);
 		j++;
-		if (j == sizeof(swirr)-1)
+		if (j == sizeof(swirr) - 1)
 			j = 0;
 
 		fprintf(stdout, "[");
@@ -135,7 +135,14 @@ int main(int argc, char **argv)
 			device_name = optarg;
 			break;
 		case 'o':
-			lines[i] = strtoul(optarg, NULL, 10);
+			/*
+			 * Avoid overflow. Do not immediately error, we want to
+			 * be able to accurately report on the amount of times
+			 *'-o' was given to give an accurate error message
+			 */
+			if (i < GPIOHANDLES_MAX)
+				lines[i] = strtoul(optarg, NULL, 10);
+
 			i++;
 			break;
 		case '?':
@@ -143,6 +150,14 @@ int main(int argc, char **argv)
 			return -1;
 		}
 	}
+
+	if (i >= GPIOHANDLES_MAX) {
+		fprintf(stderr,
+			"Only %d occurences of '-o' are allowed, %d were found\n",
+			GPIOHANDLES_MAX, i + 1);
+		return -1;
+	}
+
 	nlines = i;
 
 	if (!device_name || !nlines) {
-- 
2.24.1