[3.16.y-ckt stable] Patch "__bitmap_parselist: fix bug in empty string handling" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    __bitmap_parselist: fix bug in empty string handling

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt15.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 8905fb553334961b8e52f82271fdba71f5ec8390 Mon Sep 17 00:00:00 2001
From: Chris Metcalf <cmetcalf at ezchip.com>
Date: Thu, 25 Jun 2015 15:02:08 -0700
Subject: __bitmap_parselist: fix bug in empty string handling

commit 2528a8b8f457d7432552d0e2b6f0f4046bb702f4 upstream.

bitmap_parselist("", &mask, nmaskbits) will erroneously set bit zero in
the mask.  The same bug is visible in cpumask_parselist() since it is
layered on top of the bitmask code, e.g.  if you boot with "isolcpus=",
you will actually end up with cpu zero isolated.

The bug was introduced in commit 4b060420a596 ("bitmap, irq: add
smp_affinity_list interface to /proc/irq") when bitmap_parselist() was
generalized to support userspace as well as kernelspace.

Fixes: 4b060420a596 ("bitmap, irq: add smp_affinity_list interface to /proc/irq")
Signed-off-by: Chris Metcalf <cmetcalf at ezchip.com>
Cc: Rasmus Villemoes <linux at rasmusvillemoes.dk>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 lib/bitmap.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/lib/bitmap.c b/lib/bitmap.c
index e5c4ebe586ba..c0634aa923a6 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -603,12 +603,12 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
 	unsigned a, b;
 	int c, old_c, totaldigits;
 	const char __user __force *ubuf = (const char __user __force *)buf;
-	int exp_digit, in_range;
+	int at_start, in_range;

 	totaldigits = c = 0;
 	bitmap_zero(maskp, nmaskbits);
 	do {
-		exp_digit = 1;
+		at_start = 1;
 		in_range = 0;
 		a = b = 0;

@@ -637,11 +637,10 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
 				break;

 			if (c == '-') {
-				if (exp_digit || in_range)
+				if (at_start || in_range)
 					return -EINVAL;
 				b = 0;
 				in_range = 1;
-				exp_digit = 1;
 				continue;
 			}

@@ -651,16 +650,18 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
 			b = b * 10 + (c - '0');
 			if (!in_range)
 				a = b;
-			exp_digit = 0;
+			at_start = 0;
 			totaldigits++;
 		}
 		if (!(a <= b))
 			return -EINVAL;
 		if (b >= nmaskbits)
 			return -ERANGE;
-		while (a <= b) {
-			set_bit(a, maskp);
-			a++;
+		if (!at_start) {
+			while (a <= b) {
+				set_bit(a, maskp);
+				a++;
+			}
 		}
 	} while (buflen && c == ',');
 	return 0;