linux-kernel - [033/116] sysctl: require CAP_SYS_RAWIO to set mmap_min

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Date:	Tue, 30 Mar 2010 15:55:11 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Kees Cook <kees.cook@...onical.com>,
	Serge Hallyn <serue@...ibm.com>,
	James Morris <jmorris@...ei.org>,
	Greg Kroah-Hartman <gregkh@...e.de>
Subject: [033/116] sysctl: require CAP_SYS_RAWIO to set mmap_min_addr

2.6.32-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Kees Cook <kees.cook@...onical.com>

commit 0e1a6ef2dea88101b056b6d9984f3325c5efced3 upstream.

Currently the mmap_min_addr value can only be bypassed during mmap when
the task has CAP_SYS_RAWIO.  However, the mmap_min_addr sysctl value itself
can be adjusted to 0 if euid == 0, allowing a bypass without CAP_SYS_RAWIO.
This patch adds a check for the capability before allowing mmap_min_addr to
be changed.

Signed-off-by: Kees Cook <kees.cook@...onical.com>
Acked-by: Serge Hallyn <serue@...ibm.com>
Signed-off-by: James Morris <jmorris@...ei.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 security/min_addr.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/security/min_addr.c
+++ b/security/min_addr.c
@@ -33,6 +33,9 @@ int mmap_min_addr_handler(struct ctl_tab
 {
 	int ret;
 
+	if (!capable(CAP_SYS_RAWIO))
+		return -EPERM;
+
 	ret = proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
 
 	update_mmap_min_addr();


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