linux-kernel - [2.6 PATCH] sysctl: String length calculated is wrong if it contains negative numbers

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Message-ID: <B2EAB41A1AF603458C6A01E3CC809C4402A65361@dbde01.ent.ti.com>
Date:	Mon, 27 Nov 2006 13:36:54 +0530
From:	"BP, Praveen" <praveenbp@...com>
To:	<linux-kernel@...r.kernel.org>
Subject: [2.6 PATCH] sysctl: String length calculated is wrong if it contains negative numbers

Hi All,

In the functions do_proc_dointvec() and do_proc_doulongvec_minmax(),
there seems to be a bug in string length calculation if string contains
negative integer.

The console log given below explains the bug. Setting negative values
may not be a right thing to do for "console log level" but then the test
(given below) can be used to demonstrate the bug in the code. 

# echo "-1 -1 -1 -123456" > /proc/sys/kernel/printk
# cat /proc/sys/kernel/printk
-1      -1      -1      -1234
#
# echo "-1 -1 -1 123456" > /proc/sys/kernel/printk
# cat /proc/sys/kernel/printk
-1      -1      -1      1234
#

It works as expected if string contains all +ve integers

# echo "1 2 3 4" > /proc/sys/kernel/printk
# cat /proc/sys/kernel/printk
1       2       3       4
#

The patch given below fixes the issue.
Patch is generated against linux-2.6.18.3

Signed-off-by: Praveen BP <praveenbp@...com>

sysctl.c |    4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/sysctl.c	2006-11-19 08:58:22.000000000 +0530
+++ b/kernel/sysctl.c	2006-11-24 17:33:23.000000000 +0530
@@ -1748,7 +1748,7 @@
 			p = buf;
 			if (*p == '-' && left > 1) {
 				neg = 1;
-				left--, p++;
+				p++;
 			}
 			if (*p < '0' || *p > '9')
 				break;
@@ -1989,7 +1989,7 @@
 			p = buf;
 			if (*p == '-' && left > 1) {
 				neg = 1;
-				left--, p++;
+				p++;
 			}
 			if (*p < '0' || *p > '9')
 				break;

Thanks,
Praveen.
-
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