linux-kernel - Re: [PATCH] lib/bitmap.c: add some check to correct the parse result

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Message-Id: <20150709155701.3e3fe2cf5e7527d9aeb72338@linux-foundation.org>
Date:	Thu, 9 Jul 2015 15:57:01 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Pan Xinhui <xinhuix.pan@...el.com>
Cc:	linux-kernel@...r.kernel.org, linux@...musvillemoes.dk,
	tj@...nel.org, mnipxh@....com, Chris Metcalf <cmetcalf@...hip.com>
Subject: Re: [PATCH] lib/bitmap.c: add some check to correct the parse
 result

On Sat, 27 Jun 2015 14:36:18 +0800 Pan Xinhui <xinhuix.pan@...el.com> wrote:

> Sometimes the input from user may cause an unexpected result.
> 
> for example, echo "1-3," > /proc/irq/<xxx>/smp_affinity_list.
> The correct result should be 1-3, however we got 0-4.
> 
> To avoid this issue, we check if there is a ready digit.
> If no valid digit is set, we just continue to the next parse.
> 
> Signed-off-by: Pan Xinhui <xinhuix.pan@...el.com>
> ---
>   lib/bitmap.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/lib/bitmap.c b/lib/bitmap.c
> index 64c0926..3c489c1 100644
> --- a/lib/bitmap.c
> +++ b/lib/bitmap.c
> @@ -561,6 +561,8 @@ static int __bitmap_parselist(const char *buf, unsigned int buflen,
>   			return -EINVAL;
>   		if (b >= nmaskbits)
>   			return -ERANGE;
> +		if (unlikely(exp_digit))
> +			continue;
>   		while (a <= b) {
>   			set_bit(a, maskp);
>   			a++;

This bug might have been fixed by 2528a8b8f457d7 ("__bitmap_parselist:
fix bug in empty string handling"), below.  Please check?


commit 2528a8b8f457d7432552d0e2b6f0f4046bb702f4
Author:     Chris Metcalf <cmetcalf@...hip.com>
AuthorDate: Thu Jun 25 15:02:08 2015 -0700
Commit:     Linus Torvalds <torvalds@...ux-foundation.org>
CommitDate: Thu Jun 25 17:00:40 2015 -0700

    __bitmap_parselist: fix bug in empty string handling
    
    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@...hip.com>
    Cc: Rasmus Villemoes <linux@...musvillemoes.dk>
    Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>

diff --git a/lib/bitmap.c b/lib/bitmap.c
index 64c0926..40162f8 100644
--- a/lib/bitmap.c
+++ b/lib/bitmap.c
@@ -506,12 +506,12 @@ 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;
 
@@ -540,11 +540,10 @@ 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;
 			}
 
@@ -554,16 +553,18 @@ 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;

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