linux-kernel - [PATCH] VM/Security: add security hook to do

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Date:	Tue, 04 Dec 2007 11:06:55 -0500
From:	Eric Paris <eparis@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	jmorris@...ei.org, alan@...hat.com, chrisw@...hat.com,
	akpm@...ux-foundation.org, linux-security-module@...r.kernel.org,
	solar@...nwall.com, wtarreau@...a.kernel.org
Subject: [PATCH] VM/Security: add security hook to do_brk

Given a specifically crafted binary do_brk() can be used to get low
pages available in userspace virtually memory and can thus be used to
circumvent the mmap_min_addr low memory protection.  Add security checks
in do_brk().

Signed-off-by: Eric Paris <eparis@...hat.com>

---

 mm/mmap.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/mmap.c b/mm/mmap.c
index f4cfc6a..15678aa 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1941,6 +1941,10 @@ unsigned long do_brk(unsigned long addr, unsigned long len)
 	if (is_hugepage_only_range(mm, addr, len))
 		return -EINVAL;
 
+	error = security_file_mmap(0, 0, 0, 0, addr, 1);
+	if (error)
+		return error;
+
 	flags = VM_DATA_DEFAULT_FLAGS | VM_ACCOUNT | mm->def_flags;
 
 	error = arch_mmap_check(addr, len, flags);


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