linux-kernel - [RFC PATCH 2/3] lib/vsprintf.c: append "..." if the *pb[l] output has been truncated.

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Date:	Wed, 16 Sep 2015 11:08:42 +0200
From:	Maurizio Lombardi <mlombard@...hat.com>
To:	tj@...nel.org
Cc:	joe@...ches.com, linux@...musvillemoes.dk,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH 2/3] lib/vsprintf.c: append "..." if the *pb[l] output has been truncated.

The *pb[l] format may generate a very long string that could exaust
the output buffer capacity;
when such event happens the output could be misleading,
it may appear valid but part of it has been truncated.

This patch modifies the bitmap_*_string() functions so they will append
"..." to the output to inform the user that a truncation happened.

Signed-off-by: Maurizio Lombardi <mlombard@...hat.com>
---
 lib/vsprintf.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 8707d91..f49bf54 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -816,6 +816,7 @@ char *bitmap_string(char *buf, char *end, unsigned long *bitmap,
 	int i, chunksz;
 	bool first = true;
 	struct printf_spec spec = *specp;
+	const char *buf_start = buf;
 
 	/* reused to print numbers */
 	spec = (struct printf_spec){ .flags = SMALL | ZEROPAD, .base = 16 };
@@ -846,6 +847,29 @@ char *bitmap_string(char *buf, char *end, unsigned long *bitmap,
 
 		chunksz = CHUNKSZ;
 	}
+
+	if (buf >= end && buf_start != end) {
+		int spc = 0;
+		char *trunc = end - 1;
+
+		while (trunc > buf_start) {
+			if (*trunc == ',' && spc > 3) {
+				trunc++;
+				break;
+			}
+			trunc--;
+			spc++;
+		}
+
+		if (spc > 3) {
+			trunc[0] = '.';
+			trunc[1] = '.';
+			trunc[2] = '.';
+			trunc[3] = '\0';
+		} else
+			trunc[0] = '\0';
+	}
+
 	return buf;
 }
 
@@ -858,6 +882,7 @@ char *bitmap_list_string(char *buf, char *end, unsigned long *bitmap,
 	int cur, rbot, rtop;
 	bool first = true;
 	struct printf_spec spec = *specp;
+	const char *buf_start = buf;
 
 	/* reused to print numbers */
 	spec = (struct printf_spec){ .base = 10 };
@@ -887,6 +912,29 @@ char *bitmap_list_string(char *buf, char *end, unsigned long *bitmap,
 
 		rbot = cur;
 	}
+
+	if (buf >= end && buf_start != end) {
+		int spc = 0;
+		char *trunc = end - 1;
+
+		while (trunc > buf_start) {
+			if (*trunc == ',' && spc > 3) {
+				trunc++;
+				break;
+			}
+			trunc--;
+			spc++;
+		}
+
+		if (spc > 3) {
+			trunc[0] = '.';
+			trunc[1] = '.';
+			trunc[2] = '.';
+			trunc[3] = '\0';
+		} else
+			trunc[0] = '\0';
+	}
+
 	return buf;
 }
 
-- 
Maurizio Lombardi

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