diff mbox series

[v2,1/2] iio: core: Use scnprintf() for avoiding potential buffer overflow

Message ID 20200316124941.8010-2-tiwai@suse.de (mailing list archive)
State New, archived
Headers show
Series iio: Use scnprintf() for avoiding potential buffer overflow | expand

Commit Message

Takashi Iwai March 16, 2020, 12:49 p.m. UTC 
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(-)

Comments

Brian Masney March 16, 2020, 4:19 p.m. UTC | #1 
On Mon, Mar 16, 2020 at 01:49:40PM +0100, Takashi Iwai wrote:
> 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>

Reviewed-by: Brian Masney <masneyb@onstation.org>
Jonathan Cameron March 22, 2020, 6:06 p.m. UTC | #2 
On Mon, 16 Mar 2020 12:19:35 -0400
Brian Masney <masneyb@onstation.org> wrote:

> On Mon, Mar 16, 2020 at 01:49:40PM +0100, Takashi Iwai wrote:
> > 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>  
> 
> Reviewed-by: Brian Masney <masneyb@onstation.org>
I picked this one up from v1.

Thanks,

Jonathan
diff mbox series

Patch

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;