[PATCH 2/5] hurd: Map brk non-executable

[Sergey Bugaev]

The rest of the heap (backed by individual pages) is already mapped RW.
Mapping these pages RWX presents a security hazard.

Also, in another branch memory gets allocated using vm_allocate, which
sets memory protection to VM_PROT_DEFAULT (which is RW). The mismatch
between protections prevents Mach from coalescing the VM map entries.

Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
---
 sysdeps/mach/hurd/brk.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sysdeps/mach/hurd/brk.c b/sysdeps/mach/hurd/brk.c
index f1349495..3a335194 100644
--- a/sysdeps/mach/hurd/brk.c
+++ b/sysdeps/mach/hurd/brk.c
@@ -106,7 +106,7 @@ _hurd_set_brk (vm_address_t addr)
        /* First finish allocation.  */
        err = __vm_protect (__mach_task_self (), pagebrk,
                            alloc_start - pagebrk, 0,
-                           VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE);
+                           VM_PROT_READ|VM_PROT_WRITE);
       if (! err)
        _hurd_brk = alloc_start;
 
@@ -120,7 +120,7 @@ _hurd_set_brk (vm_address_t addr)
   else
     /* Make the memory accessible.  */
     err = __vm_protect (__mach_task_self (), pagebrk, pagend - pagebrk,
-                       0, VM_PROT_READ|VM_PROT_WRITE|VM_PROT_EXECUTE);
+                       0, VM_PROT_READ|VM_PROT_WRITE);
 
   if (err)
     return __hurd_fail (err);
-- 
2.41.0