linux-kernel - [PATCH] fix count(), compat

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Message-ID: <20080919155003.GB3114@redhat.com>
Date:	Fri, 19 Sep 2008 11:50:03 -0400
From:	Jason Baron <jbaron@...hat.com>
To:	a.p.zijlstra@...llo.nl
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] fix count(), compat_count() bounds checking

hi,

With MAX_ARG_STRINGS set to 0x7FFFFFFF, and being passed to 'count()'
and compat_count(), it would appear that the current max bounds check
of fs/exec.c:394:

	if(++i > max)
		return -E2BIG;

would never trigger. Since 'i' is of type int, so values would wrap and the
function would continue looping.

Simple fix seems to be chaning ++i to i++ and checking for '>='.

thanks,

-Jason


Signed-off-by: Jason Baron <jbaron@...hat.com>

---

 fs/compat.c |    2 +-
 fs/exec.c   |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)


diff --git a/fs/compat.c b/fs/compat.c
index 3d4d57a..2c68dd7 100644
--- a/fs/compat.c
+++ b/fs/compat.c
@@ -1233,7 +1233,7 @@ static int compat_count(compat_uptr_t __user *argv, int max)
 			if (!p)
 				break;
 			argv++;
-			if(++i > max)
+			if (i++ >= max)
 				return -E2BIG;
 		}
 	}
diff --git a/fs/exec.c b/fs/exec.c
index 9bf0476..7766839 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -389,7 +389,7 @@ static int count(char __user * __user * argv, int max)
 			if (!p)
 				break;
 			argv++;
-			if(++i > max)
+			if (i++ >= max)
 				return -E2BIG;
 			cond_resched();
 		}
--
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