linux-kernel - Re: [PATCH] Fix for binary

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Date:	Thu, 15 Dec 2011 15:07:02 -0800
From:	Michel Lespinasse <walken@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix for binary_sysctl() memory leak

binary_sysctl() calls sysctl_getname() which allocates from
names_cache slab usin __getname()

The matching function to free the name is __putname(), and not
putname() which should be used only to match getname() allocations.

This is because when auditing is enabled, putname() calls
audit_putname *instead* (not in addition) to __putname(). Then, if a
syscall is in progress, audit_putname does not release the name -
instead, it expects the name to get released when the syscall
completes, but that will happen only if audit_getname() was called
previously, i.e. if the name was allocated with getname() rather than
the naked __getname(). So, __getname() followed by putname() ends up
leaking memory.

Signed-off-by: Michel Lespinasse <walken@...gle.com>
---
 kernel/sysctl_binary.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
index e8bffbe..2ce1b30 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -1354,7 +1354,7 @@ static ssize_t binary_sysctl(const int *name, int nlen,

 	fput(file);
 out_putname:
-	putname(pathname);
+	__putname(pathname);
 out:
 	return result;
 }
-- 
1.7.3.1

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
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