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From: Takashi Iwai <tiwai@suse.de>
To: Jonathan Cameron <jic23@kernel.org>
Cc: Brian Masney <masneyb@onstation.org>, linux-iio@vger.kernel.org
Subject: [PATCH v2 1/2] iio: core: Use scnprintf() for avoiding potential buffer overflow
Date: Mon, 16 Mar 2020 13:49:40 +0100	[thread overview]
Message-ID: <20200316124941.8010-2-tiwai@suse.de> (raw)
In-Reply-To: <20200316124941.8010-1-tiwai@suse.de>

snprintf() is a hard-to-use function, it's especially difficult to use
it for concatenating substrings in a buffer with a limited size.
Since snprintf() returns the would-be-output size, not the actual
size, the subsequent use of snprintf() may go beyond the given limit
easily.  Although the current code doesn't actually overflow the
buffer, it's an incorrect usage.

This patch replaces such snprintf() calls with a safer version,
scnprintf().

Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
v1->v2: Rephrase the changelog

 drivers/iio/industrialio-core.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
index 65ff0d067018..197006b5d5c2 100644
--- a/drivers/iio/industrialio-core.c
+++ b/drivers/iio/industrialio-core.c
@@ -559,46 +559,46 @@ static ssize_t __iio_format_value(char *buf, size_t len, unsigned int type,
 
 	switch (type) {
 	case IIO_VAL_INT:
-		return snprintf(buf, len, "%d", vals[0]);
+		return scnprintf(buf, len, "%d", vals[0]);
 	case IIO_VAL_INT_PLUS_MICRO_DB:
 		scale_db = true;
 		/* fall through */
 	case IIO_VAL_INT_PLUS_MICRO:
 		if (vals[1] < 0)
-			return snprintf(buf, len, "-%d.%06u%s", abs(vals[0]),
+			return scnprintf(buf, len, "-%d.%06u%s", abs(vals[0]),
 					-vals[1], scale_db ? " dB" : "");
 		else
-			return snprintf(buf, len, "%d.%06u%s", vals[0], vals[1],
+			return scnprintf(buf, len, "%d.%06u%s", vals[0], vals[1],
 					scale_db ? " dB" : "");
 	case IIO_VAL_INT_PLUS_NANO:
 		if (vals[1] < 0)
-			return snprintf(buf, len, "-%d.%09u", abs(vals[0]),
+			return scnprintf(buf, len, "-%d.%09u", abs(vals[0]),
 					-vals[1]);
 		else
-			return snprintf(buf, len, "%d.%09u", vals[0], vals[1]);
+			return scnprintf(buf, len, "%d.%09u", vals[0], vals[1]);
 	case IIO_VAL_FRACTIONAL:
 		tmp = div_s64((s64)vals[0] * 1000000000LL, vals[1]);
 		tmp1 = vals[1];
 		tmp0 = (int)div_s64_rem(tmp, 1000000000, &tmp1);
-		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
+		return scnprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
 	case IIO_VAL_FRACTIONAL_LOG2:
 		tmp = shift_right((s64)vals[0] * 1000000000LL, vals[1]);
 		tmp0 = (int)div_s64_rem(tmp, 1000000000LL, &tmp1);
-		return snprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
+		return scnprintf(buf, len, "%d.%09u", tmp0, abs(tmp1));
 	case IIO_VAL_INT_MULTIPLE:
 	{
 		int i;
 		int l = 0;
 
 		for (i = 0; i < size; ++i) {
-			l += snprintf(&buf[l], len - l, "%d ", vals[i]);
+			l += scnprintf(&buf[l], len - l, "%d ", vals[i]);
 			if (l >= len)
 				break;
 		}
 		return l;
 	}
 	case IIO_VAL_CHAR:
-		return snprintf(buf, len, "%c", (char)vals[0]);
+		return scnprintf(buf, len, "%c", (char)vals[0]);
 	default:
 		return 0;
 	}
@@ -669,10 +669,10 @@ static ssize_t iio_format_avail_list(char *buf, const int *vals,
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
 			if (i < length - 1)
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						" ");
 			else
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						"\n");
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
@@ -685,10 +685,10 @@ static ssize_t iio_format_avail_list(char *buf, const int *vals,
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
 			if (i < length / 2 - 1)
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						" ");
 			else
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						"\n");
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
@@ -712,10 +712,10 @@ static ssize_t iio_format_avail_range(char *buf, const int *vals, int type)
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
 			if (i < 2)
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						" ");
 			else
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						"]\n");
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
@@ -728,10 +728,10 @@ static ssize_t iio_format_avail_range(char *buf, const int *vals, int type)
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
 			if (i < 2)
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						" ");
 			else
-				len += snprintf(buf + len, PAGE_SIZE - len,
+				len += scnprintf(buf + len, PAGE_SIZE - len,
 						"]\n");
 			if (len >= PAGE_SIZE)
 				return -EFBIG;
-- 
2.16.4


  reply	other threads:[~2020-03-16 12:49 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-16 12:49 [PATCH v2 0/2] iio: Use scnprintf() for avoiding potential buffer overflow Takashi Iwai
2020-03-16 12:49 ` Takashi Iwai [this message]
2020-03-16 16:19   ` [PATCH v2 1/2] iio: core: " Brian Masney
2020-03-22 18:06     ` Jonathan Cameron
2020-03-16 12:49 ` [PATCH v2 2/2] iio: tsl2772: " Takashi Iwai
2020-03-16 16:20   ` Brian Masney
2020-03-22 18:08     ` Jonathan Cameron

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