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VM/Security: add security hook to do_brk

PATCH In review Eric Paris 3 participants 3 messages Dec 4, 2007 – Dec 5, 2007

Subsystems (2)
Memory management Memory mapping
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Eric Paris

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#0 lore raw

PATCH 1/1 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 <[email protected]>

---

 mm/mmap.c |    4 ++++
 1 file changed, 4 insertions(+)
mm/mmap.c +4 -0
index f4cfc6a..15678aa 100644
@@ -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);
#1 lore raw
Quoted 6 lines · Eric Paris

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 <[email protected]>

ACK

#2 lore raw
Quoted 9 lines · Alan Cox
Quoted 6 lines · Eric Paris

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 <[email protected]>

ACK

Applied to
git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/selinux-2.6.git#for-akpm

Signature · 2 lines
James Morris
<[email protected]>