[patch 56/73] VM/Security: add security hook to do_brk(CVE-2007-6434)

[Greg KH]

2.6.23-stable review patch.  If anyone has any objections, please let us know.
------------------
From: Eric Paris <eparis@xxxxxxxxxx>

patch ecaf18c15aac8bb9bed7b7aa0e382fe252e275d5 in mainline.

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 virtual 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@xxxxxxxxxx>
Acked-by: Alan Cox <alan@xxxxxxxxxx>
Cc: Stephen Smalley <sds@xxxxxxxxxxxxx>
Cc: James Morris <jmorris@xxxxxxxxx>
Cc: Chris Wright <chrisw@xxxxxxxxxxxx>
Cc: maximilian attems <max@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

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

--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -1938,6 +1938,10 @@ unsigned long do_brk(unsigned long addr,
 	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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