linux-kernel - [PATCH 1/3] mmap: protect from stack expantion into low vm addresses

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [day] [month] [year] [list]

Message-Id: <1195246479.2924.86.camel@localhost.localdomain>
Date:	Fri, 16 Nov 2007 15:54:39 -0500
From:	Eric Paris <eparis@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	jmorris@...ei.org, sds@...ho.nsa.gov, selinux@...ho.nsa.gov,
	alan@...hat.com, chrisw@...hat.com, hpa@...or.com,
	akpm@...ux-foundation.org
Subject: [PATCH 1/3] mmap: protect from stack expantion into low vm
	addresses

When adding the new security hooks into mmap to enhance protection
against NULL pointers in the kernel I overlooked that a user may be able
to expand the stack all the way down to low addresses.  This flaw was
pointed out by a PaX/grsecurity developer and this patch should provide
protection against this missed code path.

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

---

** Be very careful applying/rediffing this patch.  Standard 3 lines of
context from git diff will misapply the first hunk to expand_upwards
instead of properly in expand_downwards.  This patch was generated using
-U 4 to make sure it applies in the correct place.  **

 mm/mmap.c |    8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

--- kernel-1/mm/mmap.c
+++ kernel-2/mm/mmap.c
@@ -1614,17 +1614,21 @@ static inline int expand_downwards(struc
 	 * so that the anon_vma locking is not a noop.
 	 */
 	if (unlikely(anon_vma_prepare(vma)))
 		return -ENOMEM;
+
+	address &= PAGE_MASK;
+	error = security_file_mmap(0, 0, 0, 0, address, 1);
+	if (error)
+		return error;
+
 	anon_vma_lock(vma);
 
 	/*
 	 * vma->vm_start/vm_end cannot change under us because the caller
 	 * is required to hold the mmap_sem in read mode.  We need the
 	 * anon_vma lock to serialize against concurrent expand_stacks.
 	 */
-	address &= PAGE_MASK;
-	error = 0;
 
 	/* Somebody else might have raced and expanded it already */
 	if (address < vma->vm_start) {
 		unsigned long size, grow;


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/