linux-kernel - [PATCH 3/3] lib/bitmap.c: bitmap_parselist can accept string with whitespaces on head or tail

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Date:	Wed, 01 Jul 2015 16:01:21 +0800
From:	Pan Xinhui <xinhuix.pan@...el.com>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:	Yury Norov <yury.norov@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rasmus Villemoes <linux@...musvillemoes.dk>, tj@...nel.org,
	peterz@...radead.org, sudeep.holla@....com, mina86@...a86.com,
	"mnipxh@....com" <mnipxh@....com>,
	Alexey Klimov <klimov.linux@...il.com>,
	"yanmin_zhang@...ux.intel.com" <yanmin_zhang@...ux.intel.com>
Subject: [PATCH 3/3] lib/bitmap.c: bitmap_parselist can accept string with
  whitespaces on head or tail


In __bitmap_parselist we can accept whitespaces on head or tail
during every parsing procedure.
If input has valid ranges, there is no reason to reject the user.

For example, bitmap_parselist(" 1-3, 5, ", &mask, nmaskbits).
After separating the string, we get " 1-3", " 5", and " ".
It's possible and reasonable to accept such string as long as
the parsing result is correct.

Signed-off-by: Pan Xinhui <xinhuix.pan@...el.com>
Cc: Yury Norov <yury.norov@...il.com>
---
  lib/bitmap.c | 32 ++++++++++++++++++--------------
  1 file changed, 18 insertions(+), 14 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index f549176..8148143 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -506,7 +506,7 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
  		int nmaskbits)
  {
  	unsigned a, b;
-	int c, old_c, totaldigits;
+	int c, old_c, totaldigits, ndigits;
  	const char __user __force *ubuf = (const char __user __force *)buf;
  	int at_start, in_range;
  
@@ -516,6 +516,7 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
  		at_start = 1;
  		in_range = 0;
  		a = b = 0;
+		ndigits = totaldigits;
  
  		/* Get the next cpu# or a range of cpu#'s */
  		while (buflen) {
@@ -529,17 +530,20 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
  			if (isspace(c))
  				continue;
  
-			/*
-			 * If the last character was a space and the current
-			 * character isn't '\0', we've got embedded whitespace.
-			 * This is a no-no, so throw an error.
-			 */
-			if (totaldigits && c && isspace(old_c))
-				return -EINVAL;
-
  			/* A '\0' or a ',' signal the end of a cpu# or range */
  			if (c == '\0' || c == ',')
  				break;
+			/*
+			* whitespaces between digits are not allowed,
+			* but it's ok if whitespaces are on head or tail.
+			* when old_c is whilespace,
+			* if totaldigits == ndigits, whitespace is on head.
+			* if whitespace is on tail, it should not run here.
+			* as c was ',' or '\0',
+			* the last code line has broken the current loop.
+			*/
+			if ((totaldigits != ndigits) && isspace(old_c))
+				return -EINVAL;
  
  			if (c == '-') {
  				if (at_start || in_range)
@@ -559,6 +563,8 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
  			at_start = 0;
  			totaldigits++;
  		}
+		if (ndigits == totaldigits)
+			continue;
  		/* if no digit is after '-', it's wrong*/
  		if (at_start && in_range)
  			return -EINVAL;
@@ -566,11 +572,9 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
  			return -EINVAL;
  		if (b >= nmaskbits)
  			return -ERANGE;
-		if (!at_start) {
-			while (a <= b) {
-				set_bit(a, maskp);
-				a++;
-			}
+		while (a <= b) {
+			set_bit(a, maskp);
+			a++;
  		}
  	} while (buflen && c == ',');
  	return 0;
-- 
1.9.1
--
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